I had to make a new iteration of my alternative electronics hat for the Turtle Rover. On the former revision G I run into trouble with external I2C due to level shifting issues. Took the chance to simplify the circuit and route I2C and RS232 directly to the Raspberry Pi header instead through ARM micro-controller. So the server software can directly access any external peripherals through kernel drivers. Hardware description available on Github.
In addition I created a experimental motor driver board with dual ST L6206 DMOS full bridge driver as a direct drop-in replacement for the L298.