The Field Stack - STspin32G4

Fellow Nerds !

The Field Stack PCB´s has arrived. I cant promise to reflow it straight away, its probably gonna take some time to set everything up. Boy oh boy fingers crossed :smiley:

Continuing this thread from here since now its not so much virtual PCB but actual reflow, programming and hopefully Field Oriented Control.


I managed to make a 3D printed frame for the stencil. No where near mass production capable, I am just hoping to succeed with a few prototypes. Had some issues with my 3D printer, getting it to print straight. Now, all that really is left to do is just to do it. I must say I regret using those tiny Molex connectors. It always bites, when going with such small pitches.

Those nails line up the PCB and the stencil pretty good.


This is cool. I have not ordered stencils before but at work I have seen a handful. Usually they are a pretty large size, even if the board is small (this is with a domestic vendor in US). How did you get such a small stencil? Cut it yourself or does JLC provide a smaller stencil? Did you just make the case from your cad file of the board outline or did they provide some dimensions for the stencil that are different from your board?

Yes, the stencils I get from JLC need to be cut down with scissors.

You Can specify pretty much everything when ordering. I just asked for 2mm larger than PCB stencil. The stencil is not stretched out, so it is not ideal. It just lines up with corner holes and get pressed down / held in place by that two part frame.

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First reflow test. No apparent shorts. The Molex 0.4mm pitch came out nice, I think (No visual shorts).

@runger placing parts, what it’s all about. Why does it take so long time to do manually. I hope this design works out, if so I will set up a PNP running SimpleFoc, closing the loop.


That’s pretty impressive, thank you. Did you use a reflow oven?

It looks beautiful! I hope it works as well as it looks, then I think you have a winner :slight_smile:


Second side came out with bridge on the MCU, the Powerstage looks ok, so all is not lost. Will try to wick the bridge. And hot-air-reflow the LDO which I placed :expressionless: wrong. Sensor breakout looks good.

Hmm… 3 solder bridges removed with flux and wick. Hope I didn’t damage the MCU…

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I gave up on doing this and would rather pay more but get it done by machine.

The external LDO I just hot-air-reflowed is now working. But the strangest thing, I know the MCU has 5v on the REGIN pin, but 0.2V on the REG3V3 pin. Maybe it’s a fuse or register or something. The MCU is still virgin. Hmm :thinking:

@runger did you try to burn/flash the STSpin32G4 already? How was the internal LDO behavior?

Edit: Maybe we have to provide 3.3v on REG3V3 while flashing first time, in order to set up the Internal LDO ?

Ahmmm, so I should have tied the external LDO EN pin (powering VDDA) to the MCU.

During power-up and power-down, the following power sequence is required:
• When VDD is below 1 V, then VDDA supply must remain below VDD + 300 mV
• When VDD is above 1 V, all power supplies became independent.

Unfortunately I think I’m 2 months behind you on this… still working on my designs, and not even finished the layout yet…

So I can’t give any feedback on experiences yet

Ok, I wonder if it’s safe to apply VM voltage before flashing the MCU?

Maybe I should ask STM.

I could just force 3.3v on the REGIN and REG3V3 circumventing the internal LDO, but that will require snipping the REGIN trace and soldering in a jumper wire. Last resort.

I guess the best way to see if the MCU has power is to hook up the ST-link and try to get a SWD connection

I believe I could apply 12V to VM without damaging anything. I suppose the buck has a default setting (8V)

Ay ay :saluting_face:

Mouse-bites brakes off easy.

No Buck functionality w. 12V on VM… No smoke either. Its like the Buck is not active.

Edit: Man! I flipped the buck diode the wrong way. That is, the symbol was flipped, and I did make a mental note to remember that. Don´t do that.

Comparing FOC SPING4 size with the Portenta light.

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Holy Guacamole

By flipping the diode, there is 8V regulated. Internal LDO outputs 3.3V. External LDOs are functioning.

Its alive!


Apparently there are two planets aligning in the sky. Jupiter and Venus ?

Edit: It really is so difficult to capture. I hope where ever you are, you have this beautiful experience.

Lets say it can drive 48V led Strings w. 5 amp on each bridge. 5 amp x 48 = 240W x 4 = 960W LED GROWTH LIGHT ( 7 amp is 1.078mW on the shunt rated for 7W). If you take the three level stack into account, it essentially is a 12 layer PCB

What are you growing?