Automotive power hat for OpenAuto

This hat is designed to work together with OpenAuto Pro and deliver some functionality which makes integrating OpenAuto into your car easier.

Work in progress - a word of warning

I'm not an electronics professional and this board is currently work in progress. If somebody is willing to do a indepth review with me I would be very glad. Reach out to me on twitter @MoJo2600.

Features

• Integrated 5A Power Supply
• Wide range power input (+7.5V to +40V)
• On-/Off circuit with ignition sensing
• 2 Digital inputs for e.g. reverse signal
• I2S sound
• RTC clock
• CSI to HDMI adapters to connect a display and camera
  • I2C bus availabe on the display connector for a light sensor
• Designed to fit exactly onto a Geekworm x825 SSD V1 (Not tested with V2 but should fit)

Connections

the following pins are used on the pi.

OpenAuto Pro Setup

Set up the device before you add the header to the raspberry pi. The device will constantly reboot if the Start / Stop script is not installed. An alternative is to bridge the 3.3V pin from the raspberry pi to BCM23.

Start / Stop script

Copy scripts/startstop.sh to the openauto device.

sudo bash startstop.sh

I2C Real Time Clock

Make sure the battery has contact to the pad on the minus size. Mine had not and I added a little bit of solder to the pad to make contact.

# select pcf85063

Rearview camera script

This script will open raspivid and show the picture of the rear camera.

Copy all files to the raspberry pi and start the setup

./setup.sh

Brightness control script

My brightness script utilizes the TSL2561 ambient light sensor. The script implements a recommendation from analog devices https://www.analog.com/en/design-notes/a-simple-implementation-of-lcd-brightness-control-using-the-max44009-ambientlight-sensor.html

Copy all files to the raspberry pi and start the setup

./setup.sh

Audio output

The current audio circuit is not really usable. The output is very noisy und the signal is too low to usw it effectively. If you want to try i t you can use the following settings.

Add the overlays to /boot/config.txt

dtoverlay=hifiberry-dac
dtoverlay=i2s-mmap

After a reboot the sound should be working. Expect a line level output. If the volume is set to high, there will be clipping.

Fixes for Issues

Bluetooth Dongle BCM20702A1 not working

I had to install the bluetooth firmware for my broadcom bluetooth dongle from this repository https://github.com/winterheart/broadcom-bt-firmware.

The error in dmesg was:

bluetooth hci1: Direct firmware load for brcm/BCM20702A1-0a5c-21e8 failed with error -2
Bluetooth: hci1: BCM: Patch brcm/BCM20702A1-0a5c-21e8 not found

The installation was easy:

wget https://github.com/winterheart/broadcom-bt-firmware/raw/master/brcm/BCM20702A1-0a5c-21e8.hcd
sudo cp *.hcd /lib/firmware/brcm/

History

Here is a picture of prototype V1 with a Mouseberry power supply.

Disclaimer

Due to the fact we are not providing a product in the legal sense, we are also not providing any warranty in any aspect.