2023-02-07 07:24 AM
I have a custom board powered by using USB, if I need to program a firmware by using the SWD feature in the ST-Link V2 Probe, may I connect just following 3 pins (without VDD) ?
- TMS_SWDIO (pin 7)
- TCK_SWCLK (pin 9)
- GND
Do I need also to connect VDD to the custom board even if the board is powered by USB ?
Thanks
2023-02-07 08:44 AM
Yes, these 3 wires will do. No need to connect VDD. On a real ST-LINK this is meant to be an input for detecting/measuring board voltage and/or connecting a level converter for 1.8V etc..
hth
KnarfB
2023-02-07 09:13 AM
Hello KnarfB,
thank you for the feedback
Just to put a detail: we are using a ST-LINK/V2-ISOL probe device.
We are using that 3 pins but the probe doesn't Connect to the board, the STM32CubeProgrammed issues an Error. This why I made that question, in order to be sure we don't need other pins.
Regards
Max
2023-02-07 09:36 AM
Haven't used the ISOL, but it make sense that VDD is needed to feed the board side of the isolated coupler, Hmm. Not sure, and don't have schematics, sorry.
hth
KnarfB
2023-02-07 11:34 AM
2023-02-07 01:35 PM
What chip, what software? Did it/something work ever before? Do you have a known good similar board like Nucelo or DK? Is the flash programmed?
2023-02-07 02:37 PM
On the authentic ST-LINK/V2 the VDD on Pin 1 (VTarget) is used to power voltage appropriate buffers
Connecting NRST is also recommended as it permits "Connect Under Reset" to work, allowing the ST-LINK to gain control of the MCU quickly/effectively, and in situations where user code may disrupt the mode/function of SWDIO/SWCLK.