I have some questions concerning the programming interface for the STM32 MCU. Putting aside the serial bootloader - am I correct to say that the absolute minimum programming (not debugging) requirement would be:-
SWDIO
SWCLK
GND
VDD
with NRST as an option. Is this a correct assumption? All the documentation I could find regarding this mention this as a debugging option and do not explicitly mention that this is sufficient for programming.
Further to this, I would just make an adapter to connect the J-Link’s 20-pin JTAG header to connect these pins to program it in this reduced mode? Is there a schematic of the adapter, assuming that some other connections need to be made such as grounding some of the JTAG pins and so on?
My objective here is to have a minimum pin-count interface (excluding a serial bootloader) and using a J-Link JTAG to do the job (thus requiring an adapter.)
Speaking only with experience with the LPC1xxxx SWD programming, reset is not an option. 3.3V is sometimes an option depending on your programmer, but generally you need 5 pins. 3.3V, GND, SWDIO, SWCLK, and RESET.
Search SWD connector for the standard 10 pin 1.27mm SWD connector. I’ve tried using a 5 pin inline connector and for some reason it’s not working for me, but if I green wire in the 10pin connector it works. I haven’t figured out why, yet.
Well, I only use 5 wires, but with the 10pin connector it always works for me, but they are pretty expensive. A 5 pin 0.1" header takes about the same space, but is cheaper. I only tried the 5 pin connector on one board, but I could not get it working for some reason. It must be something I’m doing, but I checked over the wiring over and over and couldn’t figure it out. If I just soldered wires onto the same board directly to a 10pin connector it worked fine.