Installing OpenBSD on the Pinephone

... with Crystal Kolipe ...

WARNING

The information presented on these pages is NOT intended to be followed as a guide to installing OpenBSD on your own Pinephone device, and must not be used for this purpose.

Unlike most SBCs, the Pinephone contains a rechargeable battery intended to power the device. Correct configuration of the charging circuits, including various safety features such as thermal protection will not be enabled by the current OpenBSD kernel as of the time of writing.

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General purpose I/O - LEDs, vibration motor and more!

Controlling the multi-coloured LED and vibration motor on the Pinephone is surprisingly easy, even from a simple shell script, since they are connected as GPIO devices.

All of the connections are to the gpio3 device, with pins 18, 19, and 20 controlling the green, red, and blue LED outputs respectively, and pin 2 controlling the vibration motor.

Some other devices are also connected to various gpio pins, such the backlight, and various sensors. The device tree file lists the pin assignments for these devices if you're curious. However, in the case of the backlight, since a driver for this device already exists in OpenBSD, there doesn't seem much point in trying to control it directly.

Setting up GPIO devices

To use gpio devices on OpenBSD, it's necessary to configure them before the kern.securelevel sysctl is raised during the boot process. To do this, we just need to put the relevant commands in /etc/rc.securelevel:

 gpioctl gpio3 2 set out Vibration motor
 gpioctl gpio3 18 set outGreen LED
 gpioctl gpio3 19 set outRed LED
 gpioctl gpio3 20 set outBlue LED

Then after rebooting, the configured gpio pins can be toggled from userland. It's also possible to assign a symbolic name to each of the configured pins to avoid having to hard-code pin numbers directly in the controlling program. For testing purposes, though, it's just as easy to use the numeric values.

Controlling the vibration motor

We can start and stop the vibration motor from the shell using the following commands:

 # gpioctl gpio3 2 on
 # gpioctl gpio3 2 off

Or alternatively we can toggle it to the opposite state using:

 # gpioctl gpio3 2 toggle

Setting up LED colour combinations

Since each of the red, green, and blue LED components can either be on or off, we can set a total of seven colours, or eight if we include black:

LED colour combinations

Colour              Pin 18   Pin 19   Pin 20
Black               Off      Off      Off
Blue                Off      Off      On
Red                 Off      On       Off
Magenta / Purple    Off      On       On
Green               On       Off      Off
Cyan / Turquoise    On       Off      On
Yellow              On       On       Off
White               On       On       On

The commands are similar to those used to control the vibration motor. The following will turn on the blue LED, for example:

 # gpioctl gpio3 20 on

Useful applications

Since we don't yet have any framebuffer output to the built-in display panel, adding an LED toggle to /etc/rc.local at least allows us to see if the phone is switched on and booted into the kernel, even when not connected to the serial console.

Article navigation

=> Part 1 - Building the installation media and installing. | Part 2 - Booting the completed installation and initial information gathering. | Part 3 - Starting to debug USB issues. | Part 4 - Investigating errors from sxirsb.

Part 5 - Controlling the LEDs and vibration motor.

=> Part 6 - PMIC and battery charging. | Part 7 - External keyboard battery.

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