Raspberry Pi plate/software for Foxhunting

My fascination with polar plotting gadgets lead me to try something with the Raspberry Pi. It's a fun little $35 platform with lots of IO. The main drawback I found was there are no A/D ports on the Pi, so I threw together a little plate that connects to the Pi's GPIO connector.

Since the Pi has SPI as well as a UART, I selected a MCP3202 chip. There are two A/D ports, so the first is used to acquire the S-Meter voltage, and the second can be used with a continuous-turn pot to get the antenna position (based on the front of the vehicle). The UART is used if you want to use a digital compass, the code is currently configured for the CMPS10. The code has comments, so you can see which area to comment/uncomment for either option.

The nice thing about using the digital compass is that the display is always north-up, no matter which way the vehicle is pointing. But the drawback is that it is 9600 baud serial, so when you move the antenna quickly, the display will tend to lag.

My Sequoia has a in-dash audio/video system, and with that I have a composite monitor in the dash. I used the composite out on the Pi for the main Polar display (but it is only 640x380). Big circle in the middle for the polar info, and the right side is an S-Meter thermometer. Upper left is Antenna bearing, lower left is Max Average bearing, lower right is 12-bit S-Meter (0-1024)

Python Source Code

Eagle CAD board file

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