device-tree

Device Tree Overlay and Boot Files for the Pi-puck

For more information about Linux device tree overlays on the Raspberry Pi, see https://www.raspberrypi.org/documentation/configuration/device-tree.md.

Included Hardware

The device tree overlay enables the following hardware on the Pi-puck board:

• System LEDs
• Shutdown button (optional)
• UART/Bluetooth modifications (optional)
• I2C switch
  • On-board I2C bus
    • ADC
      • Battery level inputs
      • External ADC channels (optional on kernel < 5.4)
  • e-puck I2C bus
  • Sensor board I2C buses (x6)
• Software I2C (optional)
• Audio output
• I2S microphone input

Build Instructions

A compiled copy of the device tree overlay (pi-puck.dtbo) is included . To recompile, use the following:

dtc -@ -I dts -O dtb -W no-unit_address_vs_reg -o pi-puck.dtbo pi-puck.dts

The .dtbo file should then be copied to /boot/overlays/ on the Raspberry Pi.

To enable the overlay and other GPIO options necessary for booting the Pi-puck, copy pi-puck-config.txt to /boot/ on the Raspberry Pi, and add the following to the end of /boot/config.txt:

[all]
include pi-puck-config.txt

Overlay Parameters

The device tree overlay allows certain features to be enabled, disabled or customised through parameters specified in pi-puck-config.txt.

• shutdown_key_disable disables using the aux on button as a Linux power key at a kernel level, allowing for scripts to use this button instead.
• shutdown_key_debounce sets up the debounce interval for the power button, effectively allowing a delay before shutdown is triggered (default 1000, value in milliseconds).
• bluetooth_disable disables Raspberry Pi Bluetooth and instead switches the Pi-puck UART to the PL011 controller. This is the same as using dtoverlay=pi3-disable-bt - see Raspberry Pi UART documentation.
• ain2/ain3 or ain2_soft_i2c/ain3_soft_i2c enables the external AIN2/AIN3 inputs to the ADC (on kernel < 5.4) (use _soft_i2c variants if also using soft_i2c).
• ain2_gain/ain3_gain sets the gain for the AIN2/AIN3 channels of the ADC (on kernel < 5.4) (see ads1015 documentation for values) (default 2).
• ain2_datarate/ain3_datarate sets the data rate for the AIN2/AIN3 channels of the ADC (on kernel < 5.4) (see ads1015 documentation for values) (default 4).
• soft_i2c disables the hardware I2C controller and enables a software I2C driver in its place. This can be useful for certain I2C devices that have timing issues, but causes additional CPU load when using I2C communication.
• soft_i2c_gpio_delay_us specifies the delay between GPIO operations (see i2c-gpio documentation) (default 2).