Developer Instructions

Installing specific Hardware support

Generic instructions for raspbian 2018-06-27 or later:

Download the pre-build Raspbian (both lite and full available) for the balenaFin at this link
Flash (we suggest using etcher 1.5.0+ ) and boot your device.

balenaOS / balenaCloud instructions:

Download the balenaFin (CM3) device type image (2.29.2+rev7 or later) (on balenaCloud, create a balenaFin application first, than download balenaOS clicking "add Device")
Flash (we suggest using balenaEtcher ) and boot your device.

Programming the co-processor on balenaFin

The co-processor (BGM111) SWDIO interface is exposed to the CM3L/CM3+L via bit-banged GPIO pins. This means that the co-processor can be flashed from the CM3L/CM3+L via, for example, openOCD. A reference can be found here.

Using the RTC from CM3L/CM3+L

The balenaFin sports a very common I2C RTC module that is well known, supported, and documented within the Raspberry Pi ecosystem: the DS1307.

There are plenty of guides on how to interact with the chip, including the following:

Controlling the RGB LED

balenaFin v1.1 sports a PCA9633 LED controller. This controller is mainline supported and enumerates the 3 color LEDs as sysfs led class devices in /sys/class/led/pca963x:$COLOR where $COLOR can be blue, red or green. This interface allows to set each color brightness or register a kernel trigger to each color.

Setting a color brightness: echo "$BRIGHTNESS" /sys/class/leds/pca963x\:$COLOR/brightness where $BRIGHTNESS is a value between 0 (off) and 255 (100%) and $COLOR can be blue, red or green
Registering a trigger to a color: echo "$TRIGGER" /sys/class/leds/pca963x\:$COLOR/trigger where $TRIGGER is a supported kernel trigger (like mmc0 that will make the LED behave the same as the green ACT led of the Raspberry Pi) and $COLOR can be blue, red or green

Dual camera mode

Replace the dt-blob.bin file in the boot partition of the board with this file. You can use etcher for mounting the balenaFin boot partition attached via the PRG cable (and no PSU attached!) or you can edit the OS image before flashing it onto the balenaFin.
Power off the balenaFin and unplug it from the PSU
Switch the DIP switch located on the bottom of the board, behind the Compute module (marked as #37 in the datasheet mapping section) to the CAM1 position. This operation needs to be performed with the device powered OFF!
Boot your device, you now have both cam0 and cam1 interfaces available.

Toggling the Status LED bank

This device sports 9 status LEDs varying from power, eMMC, ethernet, WiFi, WAN, etc. There is a switch which allows users to toggle them all on and off via software.

echo 511 > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio511/direction
echo 0 > /sys/class/gpio/gpio511/value # turn off
echo 1 > /sys/class/gpio/gpio511/value # turn on

Cellular via mPCIe card

We are working on identifying and documenting cards known to work out of the box on the board. If you plan on adding LTE capability to the device, we suggest the Quectel EC20EA-MINIPCIE: the card is known to work out of the box, hence only APN configuration is required. On balenaOS (2.0.0+) you do so by adding a NetworkManager profile in the boot partition under the "system-connections" folder. You can find more info about this on our docs at: https://balena.io/docs/deployment/network/2.0.0/#cellular-modem-setup.

Fin bottom with mPCIe modem

Disabling RF activity on mPCIe radio cards

echo 508 > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio508/direction
echo 1 > /sys/class/gpio/gpio508/value # mPCIe on
echo 0 > /sys/class/gpio/gpio508/value # mPCIe off

Disabling HDMI

echo 507 > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio507/direction
echo 1 > /sys/class/gpio/gpio507/value # HDMI off
echo 0 > /sys/class/gpio/gpio507/value # HDMI on

Power saving

Turn off HDMI when not required
Turn off the STATUS LEDs bank
Programmatically disable RF activity on mPCIe when not required (assumes a cellular modem is being used)
Programmatically power on and off the CM3L/CM3+L when not required via the co-processor PIN PC9 (5V interface) and PIN PF5 (3.3V interface). This is the equivalent of unplugging power from the Raspberry Pi