So I recently bought the STM32F103C8T6 "black pill" dev board along with the ST-LINK/V2 dongle (more probably a Chinese clone). After much struggling I figured out that I need to hold down the dev board's reset button for the dongle to detect the MCU but then when I connected the dongle to my STM32F429 Discovery board, it detected the F429 without having to hold down reset.
I know the connection process has a "Connect with reset" option where you connect a reset pin to the board and the dongle does the hard reset for you, but I monitored the pin and it doesn't do the reset (probably a Chinese flaw?).
It's not the end of the world, it's just weird that the 103 needs to be in reset to connect, but the 429 doesn't. The 103's SWD pins aren't assigned other functions so that's not the issue. Any insight would be greatly appreciated.
Why do I need to have the 103 in reset and not the 429?
Best Answer
A key driver of your problem is likely that the overwhelming majority of the compact little unofficial "ST-LINK" dongles do not actually drive their labeled reset pin, as the pin is connected to a different GPIO than wherever whatever firmware they are runnings thinks it is. You can verify this while watching the pin with a storage scope triggered on it. As they say, "you get what you pay for"
As a result, they won't work in a situation where you need to actually assert the target's actual reset line automatically. Substitute an actual ST-LINK or use a Discovery or Nucleo board recent enough to be able to drive the reset (the early ones could not do that either)