Using SWD with nRF52832 via custom software

[guraaf]

Hello all,

I need to program nRF52 via the SWD pins. I cannot use the nrfjprog or J-link or Segger etc. I have connected 3 wires to the nRF52 - SWCLK, SWDIO and GND.

These wires are now driven by a host and I am using the ARM reference manual for SWD at: hackipedia.org/.../IHI0031A_ARM_debug_interface_v5.pdf

or other places as well. I send the initial packet header (START, APnDP, Read, Addr, Stop, Parity etc.). However, after that, the SWDIO never turns around. The nRF52 never starts driving the SWDIO line with the ACK.

Has anyone experienced this or have any clue why this might be happening? The SWDCLK transitions happen at 100 kHZ. (clock period of 10 us). The host makes the SWDIO as input but the nRF52 doesn't drive it low.

[run_ar]

Added an attachment. Note that this is work in progress. Please let me know if this helps or not.

EDIT: had to remove the attachment due to copyright issues.

[daguro]

I had seen the drawings in that docx file before. From the drawing, I assumed that data was sampled on the negative phase of the clock, as it is in the middle of the clock cell. From the drawing, it would appear that clock cycles are delineated by the rising edge and define the set up and hold time for the negative edge which is where the data is sampled. I implemented it as such , and now need to revise my implementation.