this takes better advantage of the new UART code. Log download over
USB gets to 730 kbyte/s. For comparison, with the 4.0 code on the same
H7 we get about 300 kbyte/s
this gains about 20k of RAM, and has almost no impact on log download
speed at 921600 on a F427. The improved threading means we can afford
to have smaller buffers
this uses the ChibiOS system timer instead of a separate GPT timer for
the core ChibiOS timer. The advantage is it saves us a timer, plus it
changes ChibiOS to use a 1MHz clock on its timer, which gives us
higher resolution for delays.
This has a remarkable effect on timing jitter, reducing it greatly
Andrew Tridgell
Siddharth Purohit