Dual cam debugging

Dual cameras with dual microcontrollers has been every bit as hard as expected. It would definitely be better done with an FPGA, but the microcontrollers were on hand.

They comprise a modular component used 3 times & the FPGA would have taken some time to bring up. The FPGA would still give much better results if the system proved successful.

The SPI drops bytes from the start of the buffer & has a strange alignment requirement. The cameras are proving flaky to get started on the new board.

Debugging along the chip communication path, step by step, SPI is proving difficult to switch between transmit & receive. You need 1k resistors to keep dueling outputs from burning out, but that causes quite a degradation in signal power.

The mane surprise was that #define has proven superior to bridging pins.

Tweeking the HSI calibration value in response to frame period is all that's needed to synchronize the cameras. They automatically line up just by changing the period, but the synchronization is pretty bad. The HSI calibration value isn't as precise as hoped. It also destroys the UART output.