Programming when on external power (basic schematic ideas)

[Mecanix]

Hey folks

Just got on populating the passives and ICs on what would appear to be my first ever STM32 based controller (custom PCB). Quite successful and rather impressed with the end result although, perhaps, with the exception of being able to program (ST-Link) while external power is applied (learning harder than I thought lol).

Can someone please share a "basic" schematic that would allow for this be achieved. I understand that there are several Discovery board schematics however those shows rather complex circuits with jumpers all over & al. I'm just hoping to see if we have a far better, and "simple/r", approach to that.

Any brilliant ideas welcome, that would be kind and helpful. Thanks guys

[waclawek.jan]

> with the exception of being able to program (ST-Link) while external power is applied

Post photo of your setup.

JW

[RMcCa]

I was confused as well when designing a board for an F730, so i made connections for all 8 signals to/from an stlink2. I don't think the jtag stuff is needed, so i think you just need swd, power and ground so 5 signals/pins. The power connection to the stlink is not for powering anything but rather is used by the stlink to detect the correct voltage for interacting with the target.​

[Mecanix]

Sure. Not much going on in all honesty other than;

1) External pwr (24V to 5V) Step-down feeding a LDO (3V3)

2) PC/Programmer connecting to 3V3, SWCLK, SWDIO, GND

[Mecanix]

Tried connecting SWCLK, SWDIO, GND and leaving 3V3 disconnected and that didn't worked out. Still getting current going to the programmer. Tried a diode on the prog GND to prevent that and that didn't do anything.

[Mecanix]

If anyone have achieved programming from ST-LINK (USB/PC) and with External Power ON, it would be nice to see how you did that circuit-wise.

Basic schematic (i.e. as basic as it can get) would certainly help visualizing this.

Cheers guys

[RMcCa]

Dunno. The stlink is powered thru the usb and the target board should be powered separately. The Vcc connection between the two is for sensing on the stlink. I've had no trouble using stlink with multiple boards using 8 pogo pins to connect to pads on the f730 target board.​

[Mecanix]

I have a feeling what you are trying to say is that the programmer I am using might/could be the issue 😉 Attached is what I was given by the IC supplier, told me this is all what I needed to get balls rolling. Do I need to get myself an official ST-LINK V3 or similar to get External Power to work with PC/USB?

Given I might use the same SW interface on the official prog (i.e. SWCLK, SWDIO, 3V3, GND), would the end result (fault?) not be the same as this V2.1?

[RMcCa]

There is nothing to visualize. I'm only trying to help because I've got little to do at the moment.

The datasheet contains everything you need to know. The stlink header pinout is readily accessible. Connect pins according to their label​s.

*Edited by Moderation*

[Mecanix]

I am not bored troll. I am a mechanical engineer who've recently taken onto EEV and trying to wrap my head around several MCU technologies/circuits, particularly STM32. I am hoping to seek "best advice" from a professional/experienced community.

Am I on the right forum??