树莓派因为没有BIOS，所以Raspbian对设备的加载都是依赖在/boot/config.txt中的配置来加载。当Linux内核加载时，会读取/boot/config.txt中的设备配置和设备参数配置来把设备动态加载到Device Tree(DT)中。
1. config.txt的配置语法
dtoverlay=<device>
dtparam=<param1>,<param2>,...
-
dtoverlay上配你想要加载设备，这些设备都必须是Raspbian支持的，它们位于
/boot/overlays下。这是设备他们的说明位于/boot/overlays/README，可以在这里查看到Raspbian支持的每个设备的具体信息和参数(也可以直接在官方Github查阅最新的设备支持) -
dtparam是设备的参数，具体信息可根据
/boot/overlays/README中的说明来配置
2. Raspbian支持的设备
截止2017.09.09发布的Raspbian最新版本，其支持的设备及信息如下。
1.Raspbian版本
Raspbian stretch with desktop
version: September 2017
release date: 2017.09.07
kernel version: 4.9
debian version: stretch
设备列表
Introduction
============
This directory contains Device Tree overlays. Device Tree makes it possible
to support many hardware configurations with a single kernel and without the
need to explicitly load or blacklist kernel modules. Note that this isn't a
"pure" Device Tree configuration (c.f. MACH_BCM2835) - some on-board devices
are still configured by the board support code, but the intention is to
eventually reach that goal.
On Raspberry Pi, Device Tree usage is controlled from /boot/config.txt. By
default, the Raspberry Pi kernel boots with device tree enabled. You can
completely disable DT usage (for now) by adding:
device_tree=
to your config.txt, which should cause your Pi to revert to the old way of
doing things after a reboot.
In /boot you will find a .dtb for each base platform. This describes the
hardware that is part of the Raspberry Pi board. The loader (start.elf and its
siblings) selects the .dtb file appropriate for the platform by name, and reads
it into memory. At this point, all of the optional interfaces (i2c, i2s, spi)
are disabled, but they can be enabled using Device Tree parameters:
dtparam=i2c=on,i2s=on,spi=on
However, this shouldn't be necessary in many use cases because loading an
overlay that requires one of those interfaces will cause it to be enabled
automatically, and it is advisable to only enable interfaces if they are
needed.
Configuring additional, optional hardware is done using Device Tree overlays
(see below).
raspi-config
============
The Advanced Options section of the raspi-config utility can enable and disable
Device Tree use, as well as toggling the I2C and SPI interfaces. Note that it
is possible to both enable an interface and blacklist the driver, if for some
reason you should want to defer the loading.
Modules
=======
As well as describing the hardware, Device Tree also gives enough information
to allow suitable driver modules to be located and loaded, with the corollary
that unneeded modules are not loaded. As a result it should be possible to
remove lines from /etc/modules, and /etc/modprobe.d/raspi-blacklist.conf can
have its contents deleted (or commented out).
Using Overlays
==============
Overlays are loaded using the "dtoverlay" directive. As an example, consider
the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
pre-DT world this would be loaded from /etc/modules, with an explicit
"modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
this becomes a line in config.txt:
dtoverlay=lirc-rpi
This causes the file /boot/overlays/lirc-rpi.dtbo to be loaded. By
default it will use GPIOs 17 (out) and 18 (in), but this can be modified using
DT parameters:
dtoverlay=lirc-rpi,gpio_out_pin=17,gpio_in_pin=13
Parameters always have default values, although in some cases (e.g. "w1-gpio")
it is necessary to provided multiple overlays in order to get the desired
behaviour. See the list of overlays below for a description of the parameters
and their defaults.
The Overlay and Parameter Reference
===================================
N.B. When editing this file, please preserve the indentation levels to make it
simple to parse programmatically. NO HARD TABS.
Name: <The base DTB>
Info: Configures the base Raspberry Pi hardware
Load: <loaded automatically>
Params:
audio Set to "on" to enable the onboard ALSA audio
interface (default "off")
i2c_arm Set to "on" to enable the ARM's i2c interface
(default "off")
i2c_vc Set to "on" to enable the i2c interface
usually reserved for the VideoCore processor
(default "off")
i2c An alias for i2c_arm
i2c_arm_baudrate Set the baudrate of the ARM's i2c interface
(default "100000")
i2c_vc_baudrate Set the baudrate of the VideoCore i2c interface
(default "100000")
i2c_baudrate An alias for i2c_arm_baudrate
i2s Set to "on" to enable the i2s interface
(default "off")
spi Set to "on" to enable the spi interfaces
(default "off")
random Set to "on" to enable the hardware random
number generator (default "on")
sd_overclock Clock (in MHz) to use when the MMC framework
requests 50MHz
sd_force_pio Disable DMA support for SD driver (default off)
sd_pio_limit Number of blocks above which to use DMA for
SD card (default 1)
sd_debug Enable debug output from SD driver (default off)
uart0 Set to "off" to disable uart0 (default "on")
uart1 Set to "on" or "off" to enable or disable uart1
(default varies)
watchdog Set to "on" to enable the hardware watchdog
(default "off")
act_led_trigger Choose which activity the LED tracks.
Use "heartbeat" for a nice load indicator.
(default "mmc")
act_led_activelow Set to "on" to invert the sense of the LED
(default "off")
N.B. For Pi3 see pi3-act-led overlay.
act_led_gpio Set which GPIO to use for the activity LED
(in case you want to connect it to an external
device)
(default "16" on a non-Plus board, "47" on a
Plus or Pi 2)
N.B. For Pi3 see pi3-act-led overlay.
pwr_led_trigger
pwr_led_activelow
pwr_led_gpio
As for act_led_*, but using the PWR LED.
Not available on Model A/B boards.
N.B. It is recommended to only enable those interfaces that are needed.
Leaving all interfaces enabled can lead to unwanted behaviour (i2c_vc
interfering with Pi Camera, I2S and SPI hogging GPIO pins, etc.)
Note also that i2c, i2c_arm and i2c_vc are aliases for the physical
interfaces i2c0 and i2c1. Use of the numeric variants is still possible
but deprecated because the ARM/VC assignments differ between board
revisions. The same board-specific mapping applies to i2c_baudrate,
and the other i2c baudrate parameters.
Name: adau1977-adc
Info: Overlay for activation of ADAU1977 ADC codec over I2C for control
and I2S for data.
Load: dtoverlay=adau1977-adc
Params: <None>
Name: adau7002-simple
Info: Overlay for the activation of ADAU7002 stereo PDM to I2S converter.
Load: dtoverlay=adau7002-simple,<param>=<val>
Params: card-name Override the default, "adau7002", card name.
Name: ads1015
Info: Overlay for activation of Texas Instruments ADS1015 ADC over I2C
Load: dtoverlay=ads1015,<param>=<val>
Params: addr I2C bus address of device. Set based on how the
addr pin is wired. (default=0x48 assumes addr
is pulled to GND)
cha_enable Enable virtual channel a. (default=true)
cha_cfg Set the configuration for virtual channel a.
(default=4 configures this channel for the
voltage at A0 with respect to GND)
cha_datarate Set the datarate (samples/sec) for this channel.
(default=4 sets 1600 sps)
cha_gain Set the gain of the Programmable Gain
Amplifier for this channel. (default=2 sets the
full scale of the channel to 2.048 Volts)
Channel (ch) parameters can be set for each enabled channel.
A maximum of 4 channels can be enabled (letters a thru d).
For more information refer to the device datasheet at:
http://www.ti.com/lit/ds/symlink/ads1015.pdf
Name: ads1115
Info: Texas Instruments ADS1115 ADC
Load: dtoverlay=ads1115,<param>[=<val>]
Params: addr I2C bus address of device. Set based on how the
addr pin is wired. (default=0x48 assumes addr
is pulled to GND)
cha_enable Enable virtual channel a.
cha_cfg Set the configuration for virtual channel a.
(default=4 configures this channel for the
voltage at A0 with respect to GND)
cha_datarate Set the datarate (samples/sec) for this channel.
(default=7 sets 860 sps)
cha_gain Set the gain of the Programmable Gain
Amplifier for this channel. (Default 1 sets the
full scale of the channel to 4.096 Volts)
Channel parameters can be set for each enabled channel.
A maximum of 4 channels can be enabled (letters a thru d).
For more information refer to the device datasheet at:
http://www.ti.com/lit/ds/symlink/ads1115.pdf
Name: ads7846
Info: ADS7846 Touch controller
Load: dtoverlay=ads7846,<param>=<val>
Params: cs SPI bus Chip Select (default 1)
speed SPI bus speed (default 2MHz, max 3.25MHz)
penirq GPIO used for PENIRQ. REQUIRED
penirq_pull Set GPIO pull (default 0=none, 2=pullup)
swapxy Swap x and y axis
xmin Minimum value on the X axis (default 0)
ymin Minimum value on the Y axis (default 0)
xmax Maximum value on the X axis (default 4095)
ymax Maximum value on the Y axis (default 4095)
pmin Minimum reported pressure value (default 0)
pmax Maximum reported pressure value (default 65535)
xohms Touchpanel sensitivity (X-plate resistance)
(default 400)
penirq is required and usually xohms (60-100) has to be set as well.
Apart from that, pmax (255) and swapxy are also common.
The rest of the calibration can be done with xinput-calibrator.
See: github.com/notro/fbtft/wiki/FBTFT-on-Raspian
Device Tree binding document:
www.kernel.org/doc/Documentation/devicetree/bindings/input/ads7846.txt
Name: akkordion-iqdacplus
Info: Configures the Digital Dreamtime Akkordion Music Player (based on the
OEM IQAudIO DAC+ or DAC Zero module).
Load: dtoverlay=akkordion-iqdacplus,<param>=<val>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
dtoverlay=akkordion-iqdacplus,24db_digital_gain
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
Name: allo-boss-dac-pcm512x-audio
Info: Configures the Allo Boss DAC audio cards.
Load: dtoverlay=allo-boss-dac-pcm512x-audio,<param>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=allo-boss-dac-pcm512x-audio,
24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
slave Force Boss DAC into slave mode, using Pi a
master for bit clock and frame clock. Enable
with "dtoverlay=allo-boss-dac-pcm512x-audio,
slave"
Name: allo-digione
Info: Configures the Allo Digione audio card
Load: dtoverlay=allo-digione
Params: <None>
Name: allo-piano-dac-pcm512x-audio
Info: Configures the Allo Piano DAC (2.0/2.1) audio cards.
(NB. This initial support is for 2.0 channel audio ONLY! ie. stereo.
The subwoofer outputs on the Piano 2.1 are not currently supported!)
Load: dtoverlay=allo-piano-dac-pcm512x-audio,<param>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control.
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
Name: allo-piano-dac-plus-pcm512x-audio
Info: Configures the Allo Piano DAC (2.1) audio cards.
Load: dtoverlay=allo-piano-dac-plus-pcm512x-audio,<param>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control.
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
glb_mclk This option is only with Kali board. If enabled,
MCLK for Kali is used and PLL is disabled for
better voice quality. (default Off)
Name: at86rf233
Info: Configures the Atmel AT86RF233 802.15.4 low-power WPAN transceiver,
connected to spi0.0
Load: dtoverlay=at86rf233,<param>=<val>
Params: interrupt GPIO used for INT (default 23)
reset GPIO used for Reset (default 24)
sleep GPIO used for Sleep (default 25)
speed SPI bus speed in Hz (default 3000000)
trim Fine tuning of the internal capacitance
arrays (0=+0pF, 15=+4.5pF, default 15)
Name: audioinjector-addons
Info: Configures the audioinjector.net audio add on soundcards
Load: dtoverlay=audioinjector-addons
Params: <None>
Name: audioinjector-wm8731-audio
Info: Configures the audioinjector.net audio add on soundcard
Load: dtoverlay=audioinjector-wm8731-audio
Params: <None>
Name: audremap
Info: Switches PWM sound output to pins 12 (Right) & 13 (Left)
Load: dtoverlay=audremap,<param>=<val>
Params: swap_lr Reverse the channel allocation, which will also
swap the audio jack outputs (default off)
enable_jack Don't switch off the audio jack output
(default off)
Name: bmp085_i2c-sensor
Info: This overlay is now deprecated - see i2c-sensor
Load: dtoverlay=bmp085_i2c-sensor
Params: <None>
Name: dht11
Info: Overlay for the DHT11/DHT21/DHT22 humidity/temperature sensors
Also sometimes found with the part number(s) AM230x.
Load: dtoverlay=dht11,<param>=<val>
Params: gpiopin GPIO connected to the sensor's DATA output.
(default 4)
Name: dionaudio-loco
Info: Configures the Dion Audio LOCO DAC-AMP
Load: dtoverlay=dionaudio-loco
Params: <None>
Name: dionaudio-loco-v2
Info: Configures the Dion Audio LOCO-V2 DAC-AMP
Load: dtoverlay=dionaudio-loco-v2,<param>=<val>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=hifiberry-dacplus,24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24dB_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
Name: dpi18
Info: Overlay for a generic 18-bit DPI display
This uses GPIOs 0-21 (so no I2C, uart etc.), and activates the output
2-3 seconds after the kernel has started.
Load: dtoverlay=dpi18
Params: <None>
Name: dpi24
Info: Overlay for a generic 24-bit DPI display
This uses GPIOs 0-27 (so no I2C, uart etc.), and activates the output
2-3 seconds after the kernel has started.
Load: dtoverlay=dpi24
Params: <None>
Name: dwc-otg
Info: Selects the dwc_otg USB controller driver which has fiq support. This
is the default on all except the Pi Zero which defaults to dwc2.
Load: dtoverlay=dwc-otg
Params: <None>
Name: dwc2
Info: Selects the dwc2 USB controller driver
Load: dtoverlay=dwc2,<param>=<val>
Params: dr_mode Dual role mode: "host", "peripheral" or "otg"
g-rx-fifo-size Size of rx fifo size in gadget mode
g-np-tx-fifo-size Size of non-periodic tx fifo size in gadget
mode
[ The ds1307-rtc overlay has been deleted. See i2c-rtc. ]
Name: enc28j60
Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI0
Load: dtoverlay=enc28j60,<param>=<val>
Params: int_pin GPIO used for INT (default 25)
speed SPI bus speed (default 12000000)
Name: enc28j60-spi2
Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI2
Load: dtoverlay=enc28j60-spi2,<param>=<val>
Params: int_pin GPIO used for INT (default 39)
speed SPI bus speed (default 12000000)
Name: fe-pi-audio
Info: Configures the Fe-Pi Audio Sound Card
Load: dtoverlay=fe-pi-audio
Params: <None>
Name: goodix
Info: Enables I2C connected Goodix gt9271 multiple touch controller using
GPIOs 4 and 17 (pins 7 and 11 on GPIO header) for interrupt and reset.
Load: dtoverlay=goodix,<param>=<val>
Params: interrupt GPIO used for interrupt (default 4)
reset GPIO used for reset (default 17)
Name: googlevoicehat-soundcard
Info: Configures the Google voiceHAT soundcard
Load: dtoverlay=googlevoicehat-soundcard
Params: <None>
Name: gpio-ir
Info: Use GPIO pin as rc-core style infrared receiver input. The rc-core-
based gpio_ir_recv driver maps received keys directly to a
/dev/input/event* device, all decoding is done by the kernel - LIRC is
not required! The key mapping and other decoding parameters can be
configured by "ir-keytable" tool.
Load: dtoverlay=gpio-ir,<param>=<val>
Params: gpio_pin Input pin number. Default is 18.
gpio_pull Desired pull-up/down state (off, down, up)
Default is "down".
rc-map-name Default rc keymap (can also be changed by
ir-keytable), defaults to "rc-rc6-mce"
Name: gpio-poweroff
Info: Drives a GPIO high or low on poweroff (including halt)
Load: dtoverlay=gpio-poweroff,<param>=<val>
Params: gpiopin GPIO for signalling (default 26)
active_low Set if the power control device requires a
high->low transition to trigger a power-down.
Note that this will require the support of a
custom dt-blob.bin to prevent a power-down
during the boot process, and that a reboot
will also cause the pin to go low.
Name: gpio-shutdown
Info: Initiates a shutdown when GPIO pin changes. The given GPIO pin
is configured as an input key that generates KEY_POWER events.
This event is handled by systemd-logind by initiating a
shutdown. Systemd versions older than 225 need an udev rule
enable listening to the input device:
ACTION!="REMOVE", SUBSYSTEM=="input", KERNEL=="event*", \
SUBSYSTEMS=="platform", DRIVERS=="gpio-keys", \
ATTRS{keys}=="116", TAG+="power-switch"
This overlay only handles shutdown. After shutdown, the system
can be powered up again by driving GPIO3 low. The default
configuration uses GPIO3 with a pullup, so if you connect a
button between GPIO3 and GND (pin 5 and 6 on the 40-pin header),
you get a shutdown and power-up button.
Load: dtoverlay=gpio-shutdown,<param>=<val>
Params: gpio_pin GPIO pin to trigger on (default 3)
active_low When this is 1 (active low), a falling
edge generates a key down event and a
rising edge generates a key up event.
When this is 0 (active high), this is
reversed. The default is 1 (active low).
gpio_pull Desired pull-up/down state (off, down, up)
Default is "up".
Note that the default pin (GPIO3) has an
external pullup.
Name: hifiberry-amp
Info: Configures the HifiBerry Amp and Amp+ audio cards
Load: dtoverlay=hifiberry-amp
Params: <None>
Name: hifiberry-dac
Info: Configures the HifiBerry DAC audio card
Load: dtoverlay=hifiberry-dac
Params: <None>
Name: hifiberry-dacplus
Info: Configures the HifiBerry DAC+ audio card
Load: dtoverlay=hifiberry-dacplus,<param>=<val>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=hifiberry-dacplus,24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24dB_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
slave Force DAC+ Pro into slave mode, using Pi as
master for bit clock and frame clock.
Name: hifiberry-digi
Info: Configures the HifiBerry Digi and Digi+ audio card
Load: dtoverlay=hifiberry-digi
Params: <None>
Name: hifiberry-digi-pro
Info: Configures the HifiBerry Digi+ Pro audio card
Load: dtoverlay=hifiberry-digi-pro
Params: <None>
Name: hy28a
Info: HY28A - 2.8" TFT LCD Display Module by HAOYU Electronics
Default values match Texy's display shield
Load: dtoverlay=hy28a,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
resetgpio GPIO used to reset controller
ledgpio GPIO used to control backlight
Name: hy28b
Info: HY28B - 2.8" TFT LCD Display Module by HAOYU Electronics
Default values match Texy's display shield
Load: dtoverlay=hy28b,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
resetgpio GPIO used to reset controller
ledgpio GPIO used to control backlight
Name: i2c-bcm2708
Info: Fall back to the i2c_bcm2708 driver for the i2c_arm bus.
Load: dtoverlay=i2c-bcm2708
Params: <None>
Name: i2c-gpio
Info: Adds support for software i2c controller on gpio pins
Load: dtoverlay=i2c-gpio,<param>=<val>
Params: i2c_gpio_sda GPIO used for I2C data (default "23")
i2c_gpio_scl GPIO used for I2C clock (default "24")
i2c_gpio_delay_us Clock delay in microseconds
(default "2" = ~100kHz)
Name: i2c-mux
Info: Adds support for a number of I2C bus multiplexers on i2c_arm
Load: dtoverlay=i2c-mux,<param>=<val>
Params: pca9542 Select the NXP PCA9542 device
pca9545 Select the NXP PCA9545 device
pca9548 Select the NXP PCA9548 device
addr Change I2C address of the device (default 0x70)
[ The i2c-mux-pca9548a overlay has been deleted. See i2c-mux. ]
Name: i2c-pwm-pca9685a
Info: Adds support for an NXP PCA9685A I2C PWM controller on i2c_arm
Load: dtoverlay=i2c-pwm-pca9685a,<param>=<val>
Params: addr I2C address of PCA9685A (default 0x40)
Name: i2c-rtc
Info: Adds support for a number of I2C Real Time Clock devices
Load: dtoverlay=i2c-rtc,<param>=<val>
Params: abx80x Select one of the ABx80x family:
AB0801, AB0803, AB0804, AB0805,
AB1801, AB1803, AB1804, AB1805
ds1307 Select the DS1307 device
ds1339 Select the DS1339 device
ds3231 Select the DS3231 device
m41t62 Select the M41T62 device
mcp7940x Select the MCP7940x device
mcp7941x Select the MCP7941x device
pcf2127 Select the PCF2127 device
pcf8523 Select the PCF8523 device
pcf8563 Select the PCF8563 device
trickle-diode-type Diode type for trickle charge - "standard" or
"schottky" (ABx80x only)
trickle-resistor-ohms Resistor value for trickle charge (DS1339,
ABx80x)
wakeup-source Specify that the RTC can be used as a wakeup
source
Name: i2c-rtc-gpio
Info: Adds support for a number of I2C Real Time Clock devices
using the software i2c controller
Load: dtoverlay=i2c-rtc-gpio,<param>=<val>
Params: abx80x Select one of the ABx80x family:
AB0801, AB0803, AB0804, AB0805,
AB1801, AB1803, AB1804, AB1805
ds1307 Select the DS1307 device
ds1339 Select the DS1339 device
ds3231 Select the DS3231 device
mcp7940x Select the MCP7940x device
mcp7941x Select the MCP7941x device
pcf2127 Select the PCF2127 device
pcf8523 Select the PCF8523 device
pcf8563 Select the PCF8563 device
trickle-diode-type Diode type for trickle charge - "standard" or
"schottky" (ABx80x only)
trickle-resistor-ohms Resistor value for trickle charge (DS1339,
ABx80x)
wakeup-source Specify that the RTC can be used as a wakeup
source
i2c_gpio_sda GPIO used for I2C data (default "23")
i2c_gpio_scl GPIO used for I2C clock (default "24")
i2c_gpio_delay_us Clock delay in microseconds
(default "2" = ~100kHz)
Name: i2c-sensor
Info: Adds support for a number of I2C barometric pressure and temperature
sensors on i2c_arm
Load: dtoverlay=i2c-sensor,<param>=<val>
Params: addr Set the address for the BME280, BMP280, TMP102
or LM75
bme280 Select the Bosch Sensortronic BME280
Valid addresses 0x76-0x77, default 0x76
bmp085 Select the Bosch Sensortronic BMP085
bmp180 Select the Bosch Sensortronic BMP180
bmp280 Select the Bosch Sensortronic BMP280
Valid addresses 0x76-0x77, default 0x76
htu21 Select the HTU21 temperature and humidity sensor
lm75 Select the Maxim LM75 temperature sensor
Valid addresses 0x48-0x4f, default 0x4f
lm75addr Deprecated - use addr parameter instead
si7020 Select the Silicon Labs Si7013/20/21 humidity/
temperature sensor
tmp102 Select the Texas Instruments TMP102 temp sensor
Valid addresses 0x48-0x4b, default 0x48
Name: i2c0-bcm2708
Info: Enable the i2c_bcm2708 driver for the i2c0 bus. Not all pin combinations
are usable on all platforms.
Load: dtoverlay=i2c0-bcm2708,<param>=<val>
Params: sda0_pin GPIO pin for SDA0 (deprecated - use pins_*)
scl0_pin GPIO pin for SCL0 (deprecated - use pins_*)
pins_0_1 Use pins 0 and 1 (default)
pins_28_29 Use pins 28 and 29
pins_44_45 Use pins 44 and 45
pins_46_47 Use pins 46 and 47
Name: i2c1-bcm2708
Info: Enable the i2c_bcm2708 driver for the i2c1 bus
Load: dtoverlay=i2c1-bcm2708,<param>=<val>
Params: sda1_pin GPIO pin for SDA1 (2 or 44 - default 2)
scl1_pin GPIO pin for SCL1 (3 or 45 - default 3)
pin_func Alternative pin function (4 (alt0), 6 (alt2) -
default 4)
Name: i2s-gpio28-31
Info: move I2S function block to GPIO 28 to 31
Load: dtoverlay=i2s-gpio28-31
Params: <None>
Name: iqaudio-dac
Info: Configures the IQaudio DAC audio card
Load: dtoverlay=iqaudio-dac,<param>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=iqaudio-dac,24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
Name: iqaudio-dacplus
Info: Configures the IQaudio DAC+ audio card
Load: dtoverlay=iqaudio-dacplus,<param>=<val>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=iqaudio-dacplus,24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24db_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
auto_mute_amp If specified, unmute/mute the IQaudIO amp when
starting/stopping audio playback.
unmute_amp If specified, unmute the IQaudIO amp once when
the DAC driver module loads.
Name: iqaudio-digi-wm8804-audio
Info: Configures the IQAudIO Digi WM8804 audio card
Load: dtoverlay=iqaudio-digi-wm8804-audio,<param>=<val>
Params: card_name Override the default, "IQAudIODigi", card name.
dai_name Override the default, "IQAudIO Digi", dai name.
dai_stream_name Override the default, "IQAudIO Digi HiFi",
dai stream name.
Name: justboom-dac
Info: Configures the JustBoom DAC HAT, Amp HAT, DAC Zero and Amp Zero audio
cards
Load: dtoverlay=justboom-dac,<param>=<val>
Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
Digital volume control. Enable with
"dtoverlay=justboom-dac,24db_digital_gain"
(The default behaviour is that the Digital
volume control is limited to a maximum of
0dB. ie. it can attenuate but not provide
gain. For most users, this will be desired
as it will prevent clipping. By appending
the 24dB_digital_gain parameter, the Digital
volume control will allow up to 24dB of
gain. If this parameter is enabled, it is the
responsibility of the user to ensure that
the Digital volume control is set to a value
that does not result in clipping/distortion!)
Name: justboom-digi
Info: Configures the JustBoom Digi HAT and Digi Zero audio cards
Load: dtoverlay=justboom-digi
Params: <None>
Name: lirc-rpi
Info: Configures lirc-rpi (Linux Infrared Remote Control for Raspberry Pi)
Consult the module documentation for more details.
Load: dtoverlay=lirc-rpi,<param>=<val>
Params: gpio_out_pin GPIO for output (default "17")
gpio_in_pin GPIO for input (default "18")
gpio_in_pull Pull up/down/off on the input pin
(default "down")
sense Override the IR receive auto-detection logic:
"0" = force active-high
"1" = force active-low
"-1" = use auto-detection
(default "-1")
softcarrier Turn the software carrier "on" or "off"
(default "on")
invert "on" = invert the output pin (default "off")
debug "on" = enable additional debug messages
(default "off")
Name: mcp23017
Info: Configures the MCP23017 I2C GPIO expander
Load: dtoverlay=mcp23017,<param>=<val>
Params: gpiopin Gpio pin connected to the INTA output of the
MCP23017 (default: 4)
addr I2C address of the MCP23017 (default: 0x20)
Name: mcp23s17
Info: Configures the MCP23S08/17 SPI GPIO expanders.
If devices are present on SPI1 or SPI2, those interfaces must be enabled
with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
If interrupts are enabled for a device on a given CS# on a SPI bus, that
device must be the only one present on that SPI bus/CS#.
Load: dtoverlay=mcp23s17,<param>=<val>
Params: s08-spi<n>-<m>-present 4-bit integer, bitmap indicating MCP23S08
devices present on SPI<n>, CS#<m>
s17-spi<n>-<m>-present 8-bit integer, bitmap indicating MCP23S17
devices present on SPI<n>, CS#<m>
s08-spi<n>-<m>-int-gpio integer, enables interrupts on a single
MCP23S08 device on SPI<n>, CS#<m>, specifies
the GPIO pin to which INT output of MCP23S08
is connected.
s17-spi<n>-<m>-int-gpio integer, enables mirrored interrupts on a
single MCP23S17 device on SPI<n>, CS#<m>,
specifies the GPIO pin to which either INTA
or INTB output of MCP23S17 is connected.
Name: mcp2515-can0
Info: Configures the MCP2515 CAN controller on spi0.0
Load: dtoverlay=mcp2515-can0,<param>=<val>
Params: oscillator Clock frequency for the CAN controller (Hz)
spimaxfrequency Maximum SPI frequence (Hz)
interrupt GPIO for interrupt signal
Name: mcp2515-can1
Info: Configures the MCP2515 CAN controller on spi0.1
Load: dtoverlay=mcp2515-can1,<param>=<val>
Params: oscillator Clock frequency for the CAN controller (Hz)
spimaxfrequency Maximum SPI frequence (Hz)
interrupt GPIO for interrupt signal
Name: mcp3008
Info: Configures MCP3008 A/D converters
For devices on spi1 or spi2, the interfaces should be enabled
with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
Load: dtoverlay=mcp3008,<param>[=<val>]
Params: spi<n>-<m>-present boolean, configure device at spi<n>, cs<m>
spi<n>-<m>-speed integer, set the spi bus speed for this device
Name: midi-uart0
Info: Configures UART0 (ttyAMA0) so that a requested 38.4kbaud actually gets
31.25kbaud, the frequency required for MIDI
Load: dtoverlay=midi-uart0
Params: <None>
Name: midi-uart1
Info: Configures UART1 (ttyS0) so that a requested 38.4kbaud actually gets
31.25kbaud, the frequency required for MIDI
Load: dtoverlay=midi-uart1
Params: <None>
Name: mmc
Info: Selects the bcm2835-mmc SD/MMC driver, optionally with overclock
Load: dtoverlay=mmc,<param>=<val>
Params: overclock_50 Clock (in MHz) to use when the MMC framework
requests 50MHz
Name: mpu6050
Info: Overlay for i2c connected mpu6050 imu
Load: dtoverlay=mpu6050,<param>=<val>
Params: interrupt GPIO pin for interrupt (default 4)
Name: mz61581
Info: MZ61581 display by Tontec
Load: dtoverlay=mz61581,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
txbuflen Transmit buffer length (default 32768)
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
Name: papirus
Info: PaPiRus ePaper Screen by Pi Supply (both HAT and pHAT)
Load: dtoverlay=papirus,<param>=<val>
Params: panel Display panel (required):
1.44": e1144cs021
2.0": e2200cs021
2.7": e2271cs021
speed Display SPI bus speed
[ The pcf2127-rtc overlay has been deleted. See i2c-rtc. ]
[ The pcf8523-rtc overlay has been deleted. See i2c-rtc. ]
[ The pcf8563-rtc overlay has been deleted. See i2c-rtc. ]
Name: pi3-act-led
Info: Pi3 uses a GPIO expander to drive the LEDs which can only be accessed
from the VPU. There is a special driver for this with a separate DT
node, which has the unfortunate consequence of breaking the
act_led_gpio and act_led_activelow dtparams.
This overlay changes the GPIO controller back to the standard one and
restores the dtparams.
Load: dtoverlay=pi3-act-led,<param>=<val>
Params: activelow Set to "on" to invert the sense of the LED
(default "off")
gpio Set which GPIO to use for the activity LED
(in case you want to connect it to an external
device)
REQUIRED
Name: pi3-disable-bt
Info: Disable Pi3 Bluetooth and restore UART0/ttyAMA0 over GPIOs 14 & 15
N.B. To disable the systemd service that initialises the modem so it
doesn't use the UART, use 'sudo systemctl disable hciuart'.
Load: dtoverlay=pi3-disable-bt
Params: <None>
Name: pi3-disable-wifi
Info: Disable Pi3 onboard WiFi
Load: dtoverlay=pi3-disable-wifi
Params: <None>
Name: pi3-miniuart-bt
Info: Switch Pi3 Bluetooth function to use the mini-UART (ttyS0) and restore
UART0/ttyAMA0 over GPIOs 14 & 15. Note that this may reduce the maximum
usable baudrate.
N.B. It is also necessary to edit /lib/systemd/system/hciuart.service
and replace ttyAMA0 with ttyS0, unless you have a system with udev rules
that create /dev/serial0 and /dev/serial1, in which case use
/dev/serial1 instead because it will always be correct. Furthermore,
you must also set core_freq=250 in config.txt or the miniuart will not
work.
Load: dtoverlay=pi3-miniuart-bt
Params: <None>
Name: piscreen
Info: PiScreen display by OzzMaker.com
Load: dtoverlay=piscreen,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
Name: piscreen2r
Info: PiScreen 2 with resistive TP display by OzzMaker.com
Load: dtoverlay=piscreen2r,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
Name: pisound
Info: Configures the Blokas Labs pisound card
Load: dtoverlay=pisound
Params: <None>
Name: pitft22
Info: Adafruit PiTFT 2.2" screen
Load: dtoverlay=pitft22,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
Name: pitft28-capacitive
Info: Adafruit PiTFT 2.8" capacitive touch screen
Load: dtoverlay=pitft28-capacitive,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
touch-sizex Touchscreen size x (default 240)
touch-sizey Touchscreen size y (default 320)
touch-invx Touchscreen inverted x axis
touch-invy Touchscreen inverted y axis
touch-swapxy Touchscreen swapped x y axis
Name: pitft28-resistive
Info: Adafruit PiTFT 2.8" resistive touch screen
Load: dtoverlay=pitft28-resistive,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
Name: pitft35-resistive
Info: Adafruit PiTFT 3.5" resistive touch screen
Load: dtoverlay=pitft35-resistive,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
Name: pps-gpio
Info: Configures the pps-gpio (pulse-per-second time signal via GPIO).
Load: dtoverlay=pps-gpio,<param>=<val>
Params: gpiopin Input GPIO (default "18")
assert_falling_edge When present, assert is indicated by a falling
edge, rather than by a rising edge
Name: pwm
Info: Configures a single PWM channel
Legal pin,function combinations for each channel:
PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
N.B.:
1) Pin 18 is the only one available on all platforms, and
it is the one used by the I2S audio interface.
Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
2) The onboard analogue audio output uses both PWM channels.
3) So be careful mixing audio and PWM.
4) Currently the clock must have been enabled and configured
by other means.
Load: dtoverlay=pwm,<param>=<val>
Params: pin Output pin (default 18) - see table
func Pin function (default 2 = Alt5) - see above
clock PWM clock frequency (informational)
Name: pwm-2chan
Info: Configures both PWM channels
Legal pin,function combinations for each channel:
PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
N.B.:
1) Pin 18 is the only one available on all platforms, and
it is the one used by the I2S audio interface.
Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
2) The onboard analogue audio output uses both PWM channels.
3) So be careful mixing audio and PWM.
4) Currently the clock must have been enabled and configured
by other means.
Load: dtoverlay=pwm-2chan,<param>=<val>
Params: pin Output pin (default 18) - see table
pin2 Output pin for other channel (default 19)
func Pin function (default 2 = Alt5) - see above
func2 Function for pin2 (default 2 = Alt5)
clock PWM clock frequency (informational)
Name: qca7000
Info: I2SE's Evaluation Board for PLC Stamp micro
Load: dtoverlay=qca7000,<param>=<val>
Params: int_pin GPIO pin for interrupt signal (default 23)
speed SPI bus speed (default 12 MHz)
Name: raspidac3
Info: Configures the RaspiDAV Rev.3x audio card
Load: dtoverlay=raspidac3
Params: <None>
Name: rotary-encoder
Info: Overlay for GPIO connected rotary encoder.
Load: dtoverlay=rotary-encoder,<param>=<val>
Params: rotary0_pin_a GPIO connected to rotary encoder channel A
(default 4).
rotary0_pin_b GPIO connected to rotary encoder channel B
(default 17).
Name: rpi-backlight
Info: Raspberry Pi official display backlight driver
Load: dtoverlay=rpi-backlight
Params: <None>
Name: rpi-cirrus-wm5102
Info: Configures the Cirrus Logic Audio Card
Load: dtoverlay=rpi-cirrus-wm5102
Params: <None>
Name: rpi-dac
Info: Configures the RPi DAC audio card
Load: dtoverlay=rpi-dac
Params: <None>
Name: rpi-display
Info: RPi-Display - 2.8" Touch Display by Watterott
Load: dtoverlay=rpi-display,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
xohms Touchpanel sensitivity (X-plate resistance)
swapxy Swap x and y axis
Name: rpi-ft5406
Info: Official Raspberry Pi display touchscreen
Load: dtoverlay=rpi-ft5406
Params: <None>
Name: rpi-proto
Info: Configures the RPi Proto audio card
Load: dtoverlay=rpi-proto
Params: <None>
Name: rpi-sense
Info: Raspberry Pi Sense HAT
Load: dtoverlay=rpi-sense
Params: <None>
Name: rpi-tv
Info: Raspberry Pi TV HAT
Load: dtoverlay=rpi-tv
Params: <None>
Name: rra-digidac1-wm8741-audio
Info: Configures the Red Rocks Audio DigiDAC1 soundcard
Load: dtoverlay=rra-digidac1-wm8741-audio
Params: <None>
Name: sc16is750-i2c
Info: Overlay for the NXP SC16IS750 UART with I2C Interface
Enables the chip on I2C1 at 0x48. To select another address,
please refer to table 10 in reference manual.
Load: dtoverlay=sc16is750-i2c,<param>=<val>
Params: int_pin GPIO used for IRQ (default 24)
addr Address (default 0x48)
Name: sc16is752-spi1
Info: Overlay for the NXP SC16IS752 Dual UART with SPI Interface
Enables the chip on SPI1.
N.B.: spi1 is only accessible on devices with a 40pin header, eg:
A+, B+, Zero and PI2 B; as well as the Compute Module.
Load: dtoverlay=sc16is752-spi1,<param>=<val>
Params: int_pin GPIO used for IRQ (default 24)
Name: sdhost
Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock.
N.B. This overlay is designed for situations where the mmc driver is
the default, so it disables the other (mmc) interface - this will kill
WiFi on a Pi3. If this isn't what you want, either use the sdtweak
overlay or the new sd_* dtparams of the base DTBs.
Load: dtoverlay=sdhost,<param>=<val>
Params: overclock_50 Clock (in MHz) to use when the MMC framework
requests 50MHz
force_pio Disable DMA support (default off)
pio_limit Number of blocks above which to use DMA
(default 1)
debug Enable debug output (default off)
Name: sdio
Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
and enables SDIO via GPIOs 22-27.
Load: dtoverlay=sdio,<param>=<val>
Params: sdio_overclock SDIO Clock (in MHz) to use when the MMC
framework requests 50MHz
poll_once Disable SDIO-device polling every second
(default on: polling once at boot-time)
bus_width Set the SDIO host bus width (default 4 bits)
Name: sdio-1bit
Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
and enables 1-bit SDIO via GPIOs 22-25.
Load: dtoverlay=sdio-1bit,<param>=<val>
Params: sdio_overclock SDIO Clock (in MHz) to use when the MMC
framework requests 50MHz
poll_once Disable SDIO-device polling every second
(default on: polling once at boot-time)
Name: sdtweak
Info: Tunes the bcm2835-sdhost SD/MMC driver
N.B. This functionality is now available via the sd_* dtparams in the
base DTB.
Load: dtoverlay=sdtweak,<param>=<val>
Params: overclock_50 Clock (in MHz) to use when the MMC framework
requests 50MHz
force_pio Disable DMA support (default off)
pio_limit Number of blocks above which to use DMA
(default 1)
debug Enable debug output (default off)
Name: smi
Info: Enables the Secondary Memory Interface peripheral. Uses GPIOs 2-25!
Load: dtoverlay=smi
Params: <None>
Name: smi-dev
Info: Enables the userspace interface for the SMI driver
Load: dtoverlay=smi-dev
Params: <None>
Name: smi-nand
Info: Enables access to NAND flash via the SMI interface
Load: dtoverlay=smi-nand
Params: <None>
Name: spi-gpio35-39
Info: Move SPI function block to GPIO 35 to 39
Load: dtoverlay=spi-gpio35-39
Params: <None>
Name: spi-rtc
Info: Adds support for a number of SPI Real Time Clock devices
Load: dtoverlay=spi-rtc,<param>=<val>
Params: pcf2123 Select the PCF2123 device
Name: spi0-cs
Info: Allows the (software) CS pins for SPI0 to be changed
Load: dtoverlay=spi0-cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 8)
cs1_pin GPIO pin for CS1 (default 7)
Name: spi0-hw-cs
Info: Re-enables hardware CS/CE (chip selects) for SPI0
Load: dtoverlay=spi0-hw-cs
Params: <None>
Name: spi1-1cs
Info: Enables spi1 with a single chip select (CS) line and associated spidev
dev node. The gpio pin number for the CS line and spidev device node
creation are configurable.
N.B.: spi1 is only accessible on devices with a 40pin header, eg:
A+, B+, Zero and PI2 B; as well as the Compute Module.
Load: dtoverlay=spi1-1cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.0 (default
is 'okay' or enabled).
Name: spi1-2cs
Info: Enables spi1 with two chip select (CS) lines and associated spidev
dev nodes. The gpio pin numbers for the CS lines and spidev device node
creation are configurable.
N.B.: spi1 is only accessible on devices with a 40pin header, eg:
A+, B+, Zero and PI2 B; as well as the Compute Module.
Load: dtoverlay=spi1-2cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.0 (default
is 'okay' or enabled).
cs1_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.1 (default
is 'okay' or enabled).
Name: spi1-3cs
Info: Enables spi1 with three chip select (CS) lines and associated spidev
dev nodes. The gpio pin numbers for the CS lines and spidev device node
creation are configurable.
N.B.: spi1 is only accessible on devices with a 40pin header, eg:
A+, B+, Zero and PI2 B; as well as the Compute Module.
Load: dtoverlay=spi1-3cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
cs2_pin GPIO pin for CS2 (default 16 - BCM SPI1_CE2).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.0 (default
is 'okay' or enabled).
cs1_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.1 (default
is 'okay' or enabled).
cs2_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev1.2 (default
is 'okay' or enabled).
Name: spi2-1cs
Info: Enables spi2 with a single chip select (CS) line and associated spidev
dev node. The gpio pin number for the CS line and spidev device node
creation are configurable.
N.B.: spi2 is only accessible with the Compute Module.
Load: dtoverlay=spi2-1cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.0 (default
is 'okay' or enabled).
Name: spi2-2cs
Info: Enables spi2 with two chip select (CS) lines and associated spidev
dev nodes. The gpio pin numbers for the CS lines and spidev device node
creation are configurable.
N.B.: spi2 is only accessible with the Compute Module.
Load: dtoverlay=spi2-2cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.0 (default
is 'okay' or enabled).
cs1_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.1 (default
is 'okay' or enabled).
Name: spi2-3cs
Info: Enables spi2 with three chip select (CS) lines and associated spidev
dev nodes. The gpio pin numbers for the CS lines and spidev device node
creation are configurable.
N.B.: spi2 is only accessible with the Compute Module.
Load: dtoverlay=spi2-3cs,<param>=<val>
Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
cs2_pin GPIO pin for CS2 (default 45 - BCM SPI2_CE2).
cs0_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.0 (default
is 'okay' or enabled).
cs1_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.1 (default
is 'okay' or enabled).
cs2_spidev Set to 'disabled' to stop the creation of a
userspace device node /dev/spidev2.2 (default
is 'okay' or enabled).
Name: tinylcd35
Info: 3.5" Color TFT Display by www.tinylcd.com
Options: Touch, RTC, keypad
Load: dtoverlay=tinylcd35,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
fps Delay between frame updates
debug Debug output level {0-7}
touch Enable touch panel
touchgpio Touch controller IRQ GPIO
xohms Touchpanel: Resistance of X-plate in ohms
rtc-pcf PCF8563 Real Time Clock
rtc-ds DS1307 Real Time Clock
keypad Enable keypad
Examples:
Display with touchpanel, PCF8563 RTC and keypad:
dtoverlay=tinylcd35,touch,rtc-pcf,keypad
Old touch display:
dtoverlay=tinylcd35,touch,touchgpio=3
Name: uart1
Info: Enable uart1 in place of uart0
Load: dtoverlay=uart1,<param>=<val>
Params: txd1_pin GPIO pin for TXD1 (14, 32 or 40 - default 14)
rxd1_pin GPIO pin for RXD1 (15, 33 or 41 - default 15)
Name: vc4-fkms-v3d
Info: Enable Eric Anholt's DRM VC4 V3D driver on top of the dispmanx
display stack.
Load: dtoverlay=vc4-fkms-v3d,<param>
Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
cma-128 CMA is 128MB, 128MB-aligned
cma-96 CMA is 96MB, 128MB-aligned
cma-64 CMA is 64MB, 64MB-aligned
Name: vc4-kms-v3d
Info: Enable Eric Anholt's DRM VC4 HDMI/HVS/V3D driver. Running startx or
booting to GUI while this overlay is in use will cause interesting
lockups.
Load: dtoverlay=vc4-kms-v3d,<param>
Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
cma-128 CMA is 128MB, 128MB-aligned
cma-96 CMA is 96MB, 128MB-aligned
cma-64 CMA is 64MB, 64MB-aligned
Name: vga666
Info: Overlay for the Fen Logic VGA666 board
This uses GPIOs 2-21 (so no I2C), and activates the output 2-3 seconds
after the kernel has started.
Load: dtoverlay=vga666
Params: <None>
Name: w1-gpio
Info: Configures the w1-gpio Onewire interface module.
Use this overlay if you *don't* need a GPIO to drive an external pullup.
Load: dtoverlay=w1-gpio,<param>=<val>
Params: gpiopin GPIO for I/O (default "4")
pullup Non-zero, "on", or "y" to enable the parasitic
power (2-wire, power-on-data) feature
Name: w1-gpio-pullup
Info: Configures the w1-gpio Onewire interface module.
Use this overlay if you *do* need a GPIO to drive an external pullup.
Load: dtoverlay=w1-gpio-pullup,<param>=<val>
Params: gpiopin GPIO for I/O (default "4")
pullup Non-zero, "on", or "y" to enable the parasitic
power (2-wire, power-on-data) feature
extpullup GPIO for external pullup (default "5")
Name: wittypi
Info: Configures the wittypi RTC module.
Load: dtoverlay=wittypi,<param>=<val>
Params: led_gpio GPIO for LED (default "17")
led_trigger Choose which activity the LED tracks (default
"default-on")
Troubleshooting
===============
If you are experiencing problems that you think are DT-related, enable DT
diagnostic output by adding this to /boot/config.txt:
dtdebug=on
and rebooting. Then run:
sudo vcdbg log msg
and look for relevant messages.
Further reading
===============
This is only meant to be a quick introduction to the subject of Device Tree on
Raspberry Pi. There is a more complete explanation here:
http://www.raspberrypi.org/documentation/configuration/device-tree.md
