NixOS on Pinecube

Download / install Nix using the instructions here. Then, build an SD card image with ./build.sh. Otherwise, a prebuilt image is available here (last updated 2021-03-11). Decompress and flash with (replace /dev/sdX):

$ cat ./result/sd-image/nixos-sd-image-21.03pre-git-armv7l-linux.img.zst | zstd -d | dd of=/dev/sdX bs=1024

It should be accessible over UART2 pins (see pinout on wiki) or SSH.

• Username: nixos
• Password: nixos

This repository remains a work-in-progress, with certain features I need still not finished, including hardware accelerated encoding support.

Additional Notes

Recording from CSI camera:

• https://linux-sunxi.org/CSI#CSI_on_mainline_Linux_with_v4l2
• https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/subdev-formats.html

Streaming via rtmp:

Run a RTMP server on a machine on the network (assuming at 192.168.1.200).

On pinecube

$ media-ctl --set-v4l2 '"ov5640 1-003c":0[fmt:UYVY8_2X8/640x480@1/15]'
$ ffmpeg -s 640x480 -r 15 -i /dev/video0 -vcodec flv -f flv rtmp://192.168.1.200/live/pinecube

On receiving machine:

$ mpv "rtmp://192.168.1.200/live/pinecube" --profile=low-latency --cache-secs=1

To enable audio in the stream: (see section below for further audio details)

$ media-ctl --set-v4l2 '"ov5640 1-003c":0[fmt:UYVY8_2X8/320x240@1/15]'
$ ffmpeg -s 320x240 -r 15 -i /dev/video0 -f alsa -ac 1 -ar 22050 -i hw:0,0 -acodec libmp3lame -vcodec flv  -f flv rtmp://192.168.1.200/live/pinecube

(Ensure that Mic1 is active and unmuted using alsamixer) CPU usage while encoding required me to also lower camera resolution and also the audio sampling rate. Let me know if you find ffmpeg settings that give a good balance between quality, CPU usage, and bitrate.

Activating IR LEDs:

$ echo 1 > /sys/class/leds/pine64\:ir\:led1/brightness
$ echo 1 > /sys/class/leds/pine64\:ir\:led2/brightness

GPIO:

https://linux-sunxi.org/GPIO

$ cat /sys/kernel/debug/pinctrl/1c20800.pinctrl/pinmux-pins

gives information about pin numbering and what pins already claimed for other things

Enabling/disabling IR-cut filter

# Export gpio, set direction
$ echo 45 > /sys/class/gpio/export
$ echo out > /sys/class/gpio/gpio45/direction

# 1 to enable, 0 to disable
$ echo 1 > /sys/class/gpio/gpio45/value

Passive IR detection

# Export gpio, set direction
$ echo 199 > /sys/class/gpio/export
$ echo in > /sys/class/gpio/gpio199/direction

# Returns 1 for presence, 0 for none
$ cat /sys/class/gpio/gpio199/value

SPI NOR

The published schematic says it's a GD5F4GQ4UCYIG, however the label on the pinecube I have is for an XT25F128B. And this matches the JEDEC bytes reported in Linux.

$ sudo modprobe spi-nor

The device is accessible at /dev/mtd0.

SPI Boot

Run nix-build -A firmware-installer. Then,

$ dd if=result/firmware-installer-image.img of=/dev/sdX bs=1024

Then, use the menu option available over UART2 to install u-boot to the SPI.

I initially flashed a bad u-boot, which caused me to be unable to boot from MMC or even FEL. I was able to force the Pinecube to load into FEL by grounding the SPI0_MISO pin. Then, I could boot into u-boot and erase the SPI, returning the Pinecube to factory condition.

Ethernet

Working fine in linux, and now also u-boot with patch derived from: https://lists.denx.de/pipermail/u-boot/2020-May/413924.html S3 datasheet says it supports up to 1000Mbit, but we only have a 100Mbit PHY: H1601CG Maybe this is for easier PoE support?

USB

Working in linux, currently not in u-boot.

WIFI

Other individuals have reported WiFi is working for them with exactly the same NixOS configuration. However, it currently doesn't work for me. This may be a hardware / power issue on my device. Sometimes, iwlist wlan0 scan works fine. However, it frequently stopps working after starting wpa_supplicant. Dmesg errors:

Oct 19 06:11:31 nixos wpa_supplicant[926]: Successfully initialized wpa_supplicant
Oct 19 06:11:32 nixos kernel: sunxi-mmc 1c10000.mmc: data error, sending stop command
Oct 19 06:11:32 nixos kernel: sunxi-mmc 1c10000.mmc: send stop command failed

Audio

S3 has significant differences when compared with V3s. It has 4 audio inputs (3 mics, 1 line in), and 2 audio outputs (headphone and line out). PineCube MainBoard schematic says that the audio amplifier is connected in pin PB5 (PWM1) but in reality it is connected to PG6 (UART1_TX). Use alsamixer to ensure mic is active and unmuted.

$ ffmpeg -f alsa -ar 22050 -i hw:0,0 -acodec mp3 -f flv rtmp://192.168.1.200/live/pinecube

To test your speaker, first turn up the "Line Out" and "DAC" controls in alsamixer. Next run:

$ speaker-test -c2 -t wav
``
You should be able to hear the audio being played via the speaker.

## Power Supply
See `/sys/class/power_supply/axp20x-ac`.
See `/sys/class/power_supply/axp20x-battery/{status,capacity}`.
Green LED if power is on.
Red LED if battery is charging.