Interesting discussion. From my own testing, I’m actually not sure that this OBD brake pressure channel is the best signal to use, especially for an overlay.
I tried using brake pressure from OBD as well, and the response looked a bit strange and not very linear or consistent. What MRRIZK describes above about repeated pedal applications would probably explain some of that.
For a simple brake indicator, I’ve had better results using longitudinal acceleration from the accelerometer. It obviously doesn’t show actual pedal position or hydraulic pressure, but it represents the real braking effect on the car and tends to be much more consistent.
For detailed analysis I’d still prefer real brake pressure if a reliable CAN/RAM channel is available, but for a video overlay I think an accelerometer-based brake bar can actually work better than this particular OBD PID.
