STM32WL + ST-Link = Target no device found (Custom Board)

[MoralkaraLynn]

Hello ST Community,

My team and I have been working on a custom radio board using the STM32WLx5 MCU. We got the PCBs fabricated and have assembled three boards so far. But all the boards (one after another) kept reporting "Target no device found" while trying to program using an ST-Link V2.

Our current assumptions have been:

• Our soldering process has been cooking the STMs (I don't think this is a problem as we have used the same oven and reflow profile to solder F4s and WLs before and things were working)
• Something wrong on the schematic level (possibly with the NRST and BOOT pins)

Attached below is the STM section of the schematic:

(NOTE: We have made the NRST pullup resistor R6 as DNP and things still aren't working)

It would be of great help to gain some insight as to why this issue could be occurring.

 

Thanks,

MoralkaraLynn

 

 

[STM_Thirty2]

Did you take a loot at our Nucleo schematics for reference?

Nucleo-WL55JC 

 

Are you using a genuine STLink V2 ?

Also make sure all your software tools are up to date :STM32Cube/IDE/CLT/Programmer etc.

By default we tie our Boot0 to GND via a jumper. 

There are associated option bytes for Boot0 Pin behavior but of course you need to be able to connect to the board for that.

Some circuitry to manually reset mcu would have been nice since there was no connection made for the programmer to reset the device.

Have you probed the reset line to see if its toggling maybe the mcu is constantly resting. I would  probe around to see what insight you can get at the hardware level, voltages states etc. If you have any other boards I would assemble and test in steps starting with absolute minimum to get the mcu powered , no crystals , let it use internal oscillator and see if you can connect to it.

[MoralkaraLynn]

Did you take a loot at our Nucleo schematics for reference?

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Yes, we have referred to it in the schematic design phase. We have also referred to MB1720 and MB1849. Our implementation matches with that of STM.

 

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Are you using a genuine STLink V2 ?

Yes, I have uploaded code to a Nucleo-WL55JC1 with this very ST-Link successfully

 

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Also make sure all your software tools are up to date :STM32Cube/IDE/CLT/Programmer etc.

Updated all, issue still persists.

 

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By default we tie our Boot0 to GND via a jumper. 

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Tried via an external wire, still no luck

 

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Have you probed the reset line to see if its toggling maybe the mcu is constantly resting.

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NRST is at a solid 3.3V with a 60mVp-p noise (measured using oscilloscope)

 

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I would  probe around to see what insight you can get at the hardware level, voltages states etc.

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We probed along a lot of pins, especially the power section. Looks like the internal SMPS and LDO are functional. We obtained all voltages as mentioned in the below image (obtained from STM32WLE5 Datasheet)

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If you have any other boards I would assemble and test in steps starting with absolute minimum to get the mcu powered , no crystals , let it use internal oscillator and see if you can connect to it.

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Done this, one board has only the STM on it and we still are in the same state.

 

Additionally, we tried verifying the System ROM / Bootloader using USART by setting BOOT0 to HIGH while powering (following this post and AN3155). Used UART1, got nothing on sending the start byte.

All these results are consistent with three of our boards. At this point, we are doubting the integrity of the STMs (although purchased from Digikey)

 

Any help in making some progress would be greatly appreciated

MoralkaraLynn