tree dedeefe8fdd3d56adec947484c6b0ac0bc332221
parent 94c09a5fae61a2769d4006d27dd4a5c3d5c6169f
author Varun Sharma <vars@google.com> 1617337602 -0700
committer CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com> 1617384639 +0000

[stm32] Add pw_sys_io_stm32cubef4

The USART configurability is needed because the F429 Discovery uses
USART1 for the virtual com port through the st-link, while the F439
Nucleo uses USART3.

The actual implementation is extremely basic, only reading/writing one
byte at a time using the synchrounous API. The HAL also has interrupt
driven and DMA API's to improve performance.

Change-Id: Ia5b99df543bd75511c8daefcbc885e5651df3f86
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/39769
Commit-Queue: Varun Sharma <vars@google.com>
Reviewed-by: Ali Zhang <alizhang@google.com>