Serial Wire Debug Port Interface for nRF52832

RE: Serial Wire Debug Port Interface for nRF52832

DanielK_GarminEng — Thu, 07 Feb 2019 17:36:26 GMT

One of the things I found really confusing in ARM IHI 0031C (the official ARM spec) was the representation of the ACK bits. They're presented as a number in the reverse order from how you would see them on a scope trace. It is REALLY easy to miss that the ack bits are transmitted LSB first.

RE: Serial Wire Debug Port Interface for nRF52832

daguro — Wed, 21 Jun 2017 16:13:10 GMT

ARM CMSIS code at github.com/.../releases

RE: Serial Wire Debug Port Interface for nRF52832

RK — Sat, 03 Jun 2017 00:19:15 GMT

Nice article - rarely does anyone dive into what SWD actually does and how it works.

For anyone writing their own I always suggest starting with, or at least looking at, the ARM CMSIS-DAP code. That's designed to implement the whole CMSIS protocol with a USB front end however it does contain the full implementation of a bitbanging SWD driver, which deals with all the timing and turnaround and other details. It's easy to take that piece out and use it driven by your own code, or use it as a reference.