@@ -56,23 +56,29 @@ have its contents deleted (or commented out).
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Using Overlays
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==============
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- Overlays are loaded using the "dtoverlay" directive. As an example, consider
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- the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
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- pre-DT world this would be loaded from /etc/modules, with an explicit
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- "modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
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- this becomes a line in config.txt :
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+ Overlays are loaded using the "dtoverlay" config.txt setting. As an example,
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+ consider I2C Real Time Clock drivers. In the pre-DT world these would be loaded
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+ by writing a magic string comprising a device identifier and an I2C address to
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+ a special file in /sys/class/i2c-adapter, having first loaded the driver for
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+ the I2C interface and the RTC device - something like this :
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- dtoverlay=lirc-rpi
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+ modprobe i2c-bcm2835
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+ modprobe rtc-ds1307
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+ echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
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- This causes the file /boot/overlays/lirc-rpi.dtbo to be loaded. By
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- default it will use GPIOs 17 (out) and 18 (in), but this can be modified using
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- DT parameters:
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+ With DT enabled, this becomes a line in config.txt:
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- dtoverlay=lirc-rpi,gpio_out_pin=17,gpio_in_pin=13
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+ dtoverlay=i2c-rtc,ds1307
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- Parameters always have default values, although in some cases (e.g. "w1-gpio")
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- it is necessary to provided multiple overlays in order to get the desired
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- behaviour. See the list of overlays below for a description of the parameters
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+ This causes the file /boot/overlays/i2c-rtc.dtbo to be loaded and a "node"
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+ describing the DS1307 I2C device to be added to the Device Tree for the Pi. By
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+ default it usees address 0x68, but this can be modified with an additional DT
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+ parameter:
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+
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+ dtoverlay=i2c-rtc,ds1307,addr=0x68
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+
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+ Parameters usually have default values, although certain parameters are
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+ mandatory. See the list of overlays below for a description of the parameters
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and their defaults.
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The Overlay and Parameter Reference
@@ -292,7 +298,9 @@ Info: Analog Devices ADV7282M analogue video to CSI2 bridge.
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Uses Unicam1, which is the standard camera connector on most Pi
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variants.
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Load: dtoverlay=adv7282m,<param>=<val>
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- Params: i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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+ Params: i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
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+ Useful on Compute Modules.
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+ i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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This is required for Pi B+, 2, 0, and 0W.
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addr Overrides the I2C address (default 0x21)
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@@ -301,7 +309,9 @@ Name: adv728x-m
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Info: Analog Devices ADV728[0|1|2]-M analogue video to CSI2 bridges.
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This is a wrapper for adv7282m, and defaults to ADV7282M.
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Load: dtoverlay=adv728x-m,<param>=<val>
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- Params: i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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+ Params: i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
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+ Useful on Compute Modules.
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+ i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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This is required for Pi B+, 2, 0, and 0W.
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addr Overrides the I2C address (default 0x21)
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adv7280m Select ADV7280-M.
@@ -608,7 +618,7 @@ Load: dtoverlay=gpio-ir,<param>=<val>
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Params: gpio_pin Input pin number. Default is 18.
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gpio_pull Desired pull-up/down state (off, down, up)
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- Default is "down ".
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+ Default is "up ".
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rc-map-name Default rc keymap (can also be changed by
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ir-keytable), defaults to "rc-rc6-mce"
@@ -769,6 +779,27 @@ Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
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master for bit clock and frame clock.
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+ Name: hifiberry-dacplusadc
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+ Info: Configures the HifiBerry DAC+ADC audio card
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+ Load: dtoverlay=hifiberry-dacplusadc,<param>=<val>
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+ Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
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+ Digital volume control. Enable with
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+ "dtoverlay=hifiberry-dacplus,24db_digital_gain"
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+ (The default behaviour is that the Digital
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+ volume control is limited to a maximum of
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+ 0dB. ie. it can attenuate but not provide
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+ gain. For most users, this will be desired
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+ as it will prevent clipping. By appending
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+ the 24dB_digital_gain parameter, the Digital
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+ volume control will allow up to 24dB of
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+ gain. If this parameter is enabled, it is the
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+ responsibility of the user to ensure that
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+ the Digital volume control is set to a value
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+ that does not result in clipping/distortion!)
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+ slave Force DAC+ Pro into slave mode, using Pi as
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+ master for bit clock and frame clock.
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+
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+
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Name: hifiberry-digi
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Info: Configures the HifiBerry Digi and Digi+ audio card
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Load: dtoverlay=hifiberry-digi
@@ -1138,29 +1169,8 @@ Params: <None>
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Name: lirc-rpi
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- Info: Configures lirc-rpi (Linux Infrared Remote Control for Raspberry Pi)
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- Consult the module documentation for more details.
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- Load: dtoverlay=lirc-rpi,<param>=<val>
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- Params: gpio_out_pin GPIO for output (default "17")
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-
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- gpio_in_pin GPIO for input (default "18")
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-
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- gpio_in_pull Pull up/down/off on the input pin
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- (default "down")
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-
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- sense Override the IR receive auto-detection logic:
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- "0" = force active-high
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- "1" = force active-low
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- "-1" = use auto-detection
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- (default "-1")
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-
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- softcarrier Turn the software carrier "on" or "off"
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- (default "on")
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-
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- invert "on" = invert the output pin (default "off")
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-
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- debug "on" = enable additional debug messages
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- (default "off")
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+ Info: This overlay has been deprecated and removed - see gpio-ir
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+ Load: <Deprecated>
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Name: ltc294x
@@ -1356,7 +1366,10 @@ Info: Omnivision OV5647 camera module.
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Uses Unicam 1, which is the standard camera connector on most Pi
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variants.
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Load: dtoverlay=ov5647,<param>=<val>
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- Params: i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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+ Params: i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
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+ Useful on Compute Modules.
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+
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+ i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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This is required for Pi B+, 2, 0, and 0W.
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@@ -2015,6 +2028,9 @@ Params: 4lane Use 4 lanes (only applicable to Compute Modules
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(574Mbit/s) and 486000000 (972Mbit/s - default)
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are supported by the driver.
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+ i2c_pins_0_1 Use pins 0&1 for the I2C instead of 44&45.
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+ Useful on Compute Modules.
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+
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i2c_pins_28_29 Use pins 28&29 for the I2C instead of 44&45.
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This is required for Pi B+, 2, 0, and 0W.
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