I want to program an STM32F103C8T6 in-circuit using the SWD interface and an ST-Link. If I don't have a reset button, do I still need to connect a capacitor and pullup resistor to the NRST pin?

[KnarfB]

SWCLK+SWDIO+GND are minimum. You might want to mimic some of the existing headers depending on your probe.

NRST is optional, as TDK wrote. Might be useful if you re-configure SWCLK+SWDIO in your code and cannot do a "soft" (SWDIO triggered) reset.

VDD is sometimes misunderstood. STM probes use it to detect the board voltage level. Cheap clones might try to suppy the board via that same pin, beware.

"AN4989 Application note “STM32 microcontroller debug toolbox�? is a good read.

[Peter BENSCH]

Very many users still use the external pull-up because the MCUs of the last century had no internal current source, so indeed some kind of copy'n'paste.

This is just like how some universities still use the letters i or j as a counter for loops, even though this once came from a language called FORTRAN, where I...N were implicit integers.

Regards

/Peter