(first posting here so bear with!)
I'm a very novice embedded programmer and have hit a wall trying to use an STM32 discovery board as an ST-Link programmer to an external STM32F051K8T. I know that the hardware I have is correct as I have inherited this project from someone who had everything working and was able to program without issue.
The SWD connections are as follows:
Discovery board CN3 -> external STM32F051K8T VDD_TARGET -> VDD SWCLK -> PA14 GND -> GND SWDIO -> PA13 NRST -> NRST with NOT, pulled up to VDD with 1K SWO -> PB3
I have removed the CN2 jumpers from the discovery board, and am powering the external chip via a UART USB lead.
The only other observation I have made that might be of some use is that when I initially connect the SWD lead to the external board, an LED on it remains on (this LED is permanently on when the board is powered with the current firmware loaded onto it). When I attempt to connect to target in the ST-Link app and get the below failure message, the LED turns off and remains off until I cycle power to the board or remove the SWD lead.
14:11:34 : Can not connect to target! If you're trying to connect to an STM32W1xx device, please select Normal or HotPlug mode from Target->Settings menu. If you're trying to connect to a low frequency application , please select a lower SWD Frequency mode from Target->Settings menu. 14:12:55 : Internal command error
I have exhausted all avenues I can think of to try to get this project working so any help would be much appreciated!
2018-12-03 10:43 edit:
I'm not at liberty to share the entire schematic but here are the SWD connections. Also, power comes over USB through a UART -> I2C bridge and then regulated by a TPS61071DDCR.