This mornings catch… Made a new STM32H503CB base module. Swapped in STM32H503CB, a new 10 point 1.25 connector, my old SWD connector and a smaller SPI Flash. I also reversed 0402 trancient capacitors back to 0603 packages for now – I will reconsider moving to 0402 as I get the P&P working.
The Molex 10p connector at left have TTL IO only – CAN, USB, UART + 2 GPIO pins and 5V + GND. This will work well both as a module and as stand-alone with a small adapter board. I am out of space, but will add som TVS transient protection diodes on the back – more correctly 8 small diodes – either that or I need to use ca 5mm extra. I might consider full galvanic isolation as well if I find a solution for the 5V. Decent galvanic isolation on TTL is very straight forward, but I feel this is an overkill since we still have a galvanic isolation layer at right here towards the IO.
This SWD needs solering for dev purposes, but you can use a truck with a stick-in plug for just programming, so you do in effect have just a footprint SWD if you want to. I had no problem with this SWD over the years, but I will make some new adapter boards for it.