Help troubleshooting F7 Lightning Plus #74
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I assembled one of these from scratch - I included a gallery of pictures. I think I did ok at putting it together, but during the flash step it says I can't connect, and the st-link programmer just flashes yellow (connection error). I included some detailed pictures from my scope - I'm guessing maybe I got a part backwards or something (although I've double checked a bunch of times) I'm using an official ST-link V2 Programmer, but I do have a cheapy knockoff coming from China in case this one is having issues. Sorry for the picture spam ;). I guess I just need some pointers on where to start troubleshooting. I admit I'm not super well versed on microcontrollers - I've had a rough time just finding a pinout for this one. I did just notice U5 is missing some solder, easy to fix, but that shouldn't affect programming right?
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Replies: 3 comments 13 replies
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It may help to power the board separately and not rely on the STLink to power the board while you program it. Looks like maybe shorts on R12 and R7? Can't be sure. It's tedious, but check for any continuity between adjacent pins on the STM. Yes, all 100. |
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Good general advice. The potential shorts on the lower rows of R7 and R12 don't matter here because all those pins across all three arrays are connected to 3v3. Hence they're electrically connected anyway. |
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I noticed that as well, but there's actually a trace between those two pins so I think its ok (that side is basically one big plane anyhow). I'll test every adjacent pin on the microcontroller as well. Visually (under the microscope) they all look perfect. I did test continuity between the chip and the pad for each pin as well - every appears to be soldered on there. |
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The big gotcha here is that the official ST-Link does not provide power. Its VCC pin is an input to power its level shifters, so it can work safely with different voltage levels (eg, 1.8v, 3.3v). So, you need to provide external power or, more easily, just hook up your ST-Link clone because those DO provide 3v3 and 5v power. Just make sure to hook up the 3v3 ;) I should have mentioned this big gotcha in the wiki. That's now fixed. Your soldering looks great, but a couple of points:
Be very careful messing with XO1. If you get stray solder on the package I've found they no longer work. Hot air it off, and I would probably hot air it back on again with more flux. |
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Woot! It connects, and I see the memory and the device id. When I go to write and verify I get an internal command error, but it actually detects the mcu now! I tested the vdd pin (1) and its at 1.7 volts.
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I would try and separately power the Greaseweazle rather than use the ST-Link power. For example, just connect a USB lead to the USB-B connector, with the PWR_SEL jumpered to USB. And disconnect 3.3v from the programming header! |
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You know what ultimately "solved it" was a work-around. I found that the programmer didn't like it when the device was powered by usb or bench power supply (for whatever reason). Running a jumper between 3.3v and acc (pin 1) worked around this - and it works! Thank you everyone for your patience and help :). |
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Oh yes pin 1 on the programmer has to be fed target voltage:
So yes jumpering 1 to 19 is fine! Or you could have powered from USB, and connected pin 1 (not 19!) to 3.3v on the board. Anyway, problem solved. Hopefully your board flashes the ACT LED three times now? Just waiting for the external XO. |
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Yup - it just flashes 3x, but I'll be able to fix the crystal tomorrow (I think). I'll just use hot air to attach it to the pcb this go so I don't end up grounding the top part to the bottom part. |
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I thought I'd follow up :) - it works perfectly fine now. I installed a new crystal using just hot air today. I just need to learn the command line options and all the associated utilities: https://twitter.com/Angelworks42/status/1357133005332963328 (some old Samsung 3.5" floppy). Edit: Oh and too add thank you very much again for everyone's patience and help :)! |
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The big gotcha here is that the official ST-Link does not provide power. Its VCC pin is an input to power its level shifters, so it can work safely with different voltage levels (eg, 1.8v, 3.3v). So, you need to provide external power or, more easily, just hook up your ST-Link clone because those DO provide 3v3 and 5v power. Just make sure to hook up the 3v3 ;)
I should have mentioned this big gotcha in the wiki. That's now fixed.
Your soldering looks great, but a couple of points:
Be very careful messing with XO1. If you get stray solder on the package I've found they no longer work. Hot air it off, and I would probably hot air it ba…