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README
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README
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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).
GPIO numbering uses the hardware pin numbering scheme (aka BCM scheme) and
not the physical pin numbers.
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" config.txt setting. As an example,
consider I2C Real Time Clock drivers. In the pre-DT world these would be loaded
by writing a magic string comprising a device identifier and an I2C address to
a special file in /sys/class/i2c-adapter, having first loaded the driver for
the I2C interface and the RTC device - something like this:
modprobe i2c-bcm2835
modprobe rtc-ds1307
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
With DT enabled, this becomes a line in config.txt:
dtoverlay=i2c-rtc,ds1307
This causes the file /boot/overlays/i2c-rtc.dtbo to be loaded and a "node"
describing the DS1307 I2C device to be added to the Device Tree for the Pi. By
default it usees address 0x68, but this can be modified with an additional DT
parameter:
dtoverlay=i2c-rtc,ds1307,addr=0x68
Parameters usually have default values, although certain parameters are
mandatory. 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")
axiperf Set to "on" to enable the AXI bus performance
monitors.
See /sys/kernel/debug/raspberrypi_axi_monitor
for the results.
eee Enable Energy Efficient Ethernet support for
compatible devices (default "on"). See also
"tx_lpi_timer".
eth_downshift_after Set the number of auto-negotiation failures
after which the 1000Mbps modes are disabled.
Legal values are 2, 3, 4, 5 and 0, where
0 means never downshift (default 2).
eth_led0 Set mode of LED0 (usually orange) (default
"1"). The legal values are:
0=link/activity 1=link1000/activity
2=link100/activity 3=link10/activity
4=link100/1000/activity 5=link10/1000/activity
6=link10/100/activity 14=off 15=on
eth_led1 Set mode of LED1 (usually green) (default
"6"). See eth_led0 for legal values.
eth_max_speed Set the maximum speed a link is allowed
to negotiate. Legal values are 10, 100 and
1000 (default 1000).
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)
sdio_overclock Clock (in MHz) to use when the MMC framework
requests 50MHz for the SDIO/WiFi interface.
tx_lpi_timer Set the delay in microseconds between going idle
and entering the low power state (default 600).
Requires EEE to be enabled - see "eee".
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: adv7282m
Info: Analog Devices ADV7282M analogue video to CSI2 bridge.
Uses Unicam1, which is the standard camera connector on most Pi
variants.
Load: dtoverlay=adv7282m,<param>=<val>
Params: i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
Useful on Compute Modules.
i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
This is required for Pi B+, 2, 0, and 0W.
addr Overrides the I2C address (default 0x21)
Name: adv728x-m
Info: Analog Devices ADV728[0|1|2]-M analogue video to CSI2 bridges.
This is a wrapper for adv7282m, and defaults to ADV7282M.
Load: dtoverlay=adv728x-m,<param>=<val>
Params: i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
Useful on Compute Modules.
i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
This is required for Pi B+, 2, 0, and 0W.
addr Overrides the I2C address (default 0x21)
adv7280m Select ADV7280-M.
adv7281m Select ADV7281-M.
adv7281ma Select ADV7281-MA.
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-katana-dac-audio
Info: Configures the Allo Katana DAC audio card
Load: dtoverlay=allo-katana-dac-audio
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: applepi-dac
Info: Configures the Orchard Audio ApplePi-DAC audio card
Load: dtoverlay=applepi-dac
Params: <None>
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,<param>=<val>
Params: non-stop-clocks Keeps the clocks running even when the stream
is paused or stopped (default off)
Name: audioinjector-ultra
Info: Configures the audioinjector.net ultra soundcard
Load: dtoverlay=audioinjector-ultra
Params: <None>
Name: audioinjector-wm8731-audio
Info: Configures the audioinjector.net audio add on soundcard
Load: dtoverlay=audioinjector-wm8731-audio
Params: <None>
Name: audiosense-pi
Info: Configures the audiosense-pi add on soundcard
For more information refer to
https://gitlab.com/kakar0t/audiosense-pi
Load: dtoverlay=audiosense-pi
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: balena-fin
Info: Overlay that enables WiFi, Bluetooth and the GPIO expander on the
balenaFin carrier board for the Raspberry Pi Compute Module 3/3+ Lite.
Load: dtoverlay=balena-fin
Params: <None>
Name: bmp085_i2c-sensor
Info: This overlay is now deprecated - see i2c-sensor
Load: <Deprecated>
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: draws
Info: Configures the NW Digital Radio DRAWS Hat
The board includes an ADC to measure various board values and also
provides two analog user inputs on the expansion header. The ADC
can be configured for various sample rates and gain values to adjust
the input range. Tables describing the two parameters follow.
ADC Gain Values:
0 = +/- 6.144V
1 = +/- 4.096V
2 = +/- 2.048V
3 = +/- 1.024V
4 = +/- 0.512V
5 = +/- 0.256V
6 = +/- 0.256V
7 = +/- 0.256V
ADC Datarate Values:
0 = 128sps
1 = 250sps
2 = 490sps
3 = 920sps
4 = 1600sps (default)
5 = 2400sps
6 = 3300sps
7 = 3300sps
Load: dtoverlay=draws,<param>=<val>
Params: draws_adc_ch4_gain Sets the full scale resolution of the ADCs
input voltage sensor (default 1)
draws_adc_ch4_datarate Sets the datarate of the ADCs input voltage
sensor
draws_adc_ch5_gain Sets the full scale resolution of the ADCs
5V rail voltage sensor (default 1)
draws_adc_ch5_datarate Sets the datarate of the ADCs 4V rail voltage
sensor
draws_adc_ch6_gain Sets the full scale resolution of the ADCs
AIN2 input (default 2)
draws_adc_ch6_datarate Sets the datarate of the ADCs AIN2 input
draws_adc_ch7_gain Sets the full scale resolution of the ADCs
AIN3 input (default 2)
draws_adc_ch7_datarate Sets the datarate of the ADCs AIN3 input
alsaname Name of the ALSA audio device (default "draws")
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: exc3000
Info: Enables I2C connected EETI EXC3000 multiple touch controller using
GPIO 4 (pin 7 on GPIO header) for interrupt.
Load: dtoverlay=exc3000,<param>=<val>
Params: interrupt GPIO used for interrupt (default 4)
sizex Touchscreen size x (default 4096)
sizey Touchscreen size y (default 4096)
invx Touchscreen inverted x axis
invy Touchscreen inverted y axis
swapxy Touchscreen swapped x y axis
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-fan
Info: Configure a GPIO pin to control a cooling fan.
Load: dtoverlay=gpio-fan,<param>=<val>
Params: gpiopin GPIO used to control the fan (default 12)
temp Temperature at which the fan switches on, in
millicelcius (default 55000)
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 "up".
rc-map-name Default rc keymap (can also be changed by
ir-keytable), defaults to "rc-rc6-mce"
Name: gpio-ir-tx
Info: Use GPIO pin as bit-banged infrared transmitter output.
This is an alternative to "pwm-ir-tx". gpio-ir-tx doesn't require
a PWM so it can be used together with onboard analog audio.
Load: dtoverlay=gpio-ir-tx,<param>=<val>
Params: gpio_pin Output GPIO (default 18)
invert "1" = invert the output (make it active-low).
Default is "0" (active-high).
Name: gpio-key
Info: This is a generic overlay for activating GPIO keypresses using
the gpio-keys library and this dtoverlay. Multiple keys can be
set up using multiple calls to the overlay for configuring
additional buttons or joysticks. You can see available keycodes
at https://github.com/torvalds/linux/blob/v4.12/include/uapi/
linux/input-event-codes.h#L64
Load: dtoverlay=gpio-key,<param>=<val>
Params: gpio 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
label Set a label for the key
keycode Set the key code for the button
Name: gpio-no-bank0-irq
Info: Use this overlay to disable GPIO interrupts for GPIOs in bank 0 (0-27),
which can be useful for UIO drivers.
N.B. Using this overlay will trigger a kernel WARN during booting, but
this can safely be ignored - the system should work as expected.
Load: dtoverlay=gpio-no-bank0-irq
Params: <None>
Name: gpio-no-irq
Info: Use this overlay to disable all GPIO interrupts, which can be useful
for user-space GPIO edge detection systems.
Load: dtoverlay=gpio-no-irq
Params: <None>
Name: gpio-poweroff
Info: Drives a GPIO high or low on poweroff (including halt). Enabling this
overlay will prevent the ability to boot by driving GPIO3 low.
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.
input Set if the gpio pin should be configured as
an input.
export Set to export the configured pin to sysfs
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: hd44780-lcd
Info: Configures an HD44780 compatible LCD display. Uses 4 gpio pins for
data, 2 gpio pins for enable and register select and 1 optional pin
for enabling/disabling the backlight display.
Load: dtoverlay=hd44780-lcd,<param>=<val>
Params: pin_d4 GPIO pin for data pin D4 (default 6)
pin_d5 GPIO pin for data pin D5 (default 13)
pin_d6 GPIO pin for data pin D6 (default 19)
pin_d7 GPIO pin for data pin D7 (default 26)
pin_en GPIO pin for "Enable" (default 21)
pin_rs GPIO pin for "Register Select" (default 20)
pin_bl Optional pin for enabling/disabling the
display backlight. (default disabled)
display_height Height of the display in characters
display_width Width of the display in characters
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-dacplusadc
Info: Configures the HifiBerry DAC+ADC audio card
Load: dtoverlay=hifiberry-dacplusadc,<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: hy28b-2017
Info: HY28B 2017 version - 2.8" TFT LCD Display Module by HAOYU Electronics
Default values match Texy's display shield
Load: dtoverlay=hy28b-2017,<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: i-sabre-q2m
Info: Configures the Audiophonics I-SABRE Q2M DAC
Load: dtoverlay=i-sabre-q2m
Params: <None>
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)
bus Set to a unique, non-zero value if wanting
multiple i2c-gpio busses. If set, will be used
as the preferred bus number (/dev/i2c-<n>). If
not set, the default value is 0, but the bus
number will be dynamically assigned - probably
3.
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
rv3028 Select the Micro Crystal RV3028 device
addr Sets the address for the RTC. Note that the
device must be configured to use the specified
address.