MIOS 32 Not Showing Up Under MIDI In/Out

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Howdy,

I’m assembling a LoopA and am at the point of pluggin it into the computer to install the software. The power LED lights up and the LED on the MCU daughter board lights as well. At that point I was hoping to be able to select “MIOS 32” from the MIDI In/Out menu but alas, it is not showing up.

I have tried both Windows and Mac versions of the software.

Any suggestions???

Thanks in advance,

Ed.

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Hi Ed,
sorry to hear about this - in the end @latigid on will be able to help best, as he designs all the hardware and knows everything best - but here are some ideas upfront:

a) Could you try another USB cable? You would not believe how many USB connection problems we experienced because of either broken USB cables or ones that supply power only.
b) Could you check that the Waveshare MCU board orientation is correct and that all headers are inserted firmly?
c) Could you check the two switches on the Waveshare PCB? One sets the power supply mode, the other the boot address, both must be correctly set.
d) Did you install the resistor R101 and the nearby region components? This is required for a proper bootup of the STM32 microcontroller.
e) could you check the soldering around the phyisical USB connector, the TVS diode (is the orientation correct??) and around the bottom of the Waveshare headers? It could be that one USB line is interrupted, e.g. due to an unwanted soldering short or maybe the TVS diode installed the wrong way. Andy could probably give you a pointer which signal goes to which final pin on the STM32 microcontroller - you could trace the USB RX and TX pins all the way from the physical USB connector up to the microcontroller pins to be sure there is connectivity - my guess is that we have an interruption here.

If nothing helps, if you could upload high-resolution pictures of the bottom and top of the core PCB, we could have a closer look.

Best regards and good luck!
Peter

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Thanks for the comprehensive response Hawkeye.

“d) Did you install the resistor R101 and the nearby region components? This is required for a proper bootup of the STM32 microcontroller.”

I have not installed theses so this looks like a good place to start. I will populate and try it again!

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I populated r101 and r102 but no luck. Is there something else around those resistors that I should populate also?

I have attempted to attach some hi-res photos. Note: the electronics shop only had 1w 330r resistors hence why r102 looks like it does…

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Hi,

As a first step, switch the waveshare board back to USB power and use a micro cable to connect directly. That would check if the board itself is okay. Switch it back after for normal LoopA operation.

I can’t really make out the TVS diode or the resistors by the USB port. The largest pin of the TVS diode is located by the silkscreen “corner” mark, so if the pin is in any other corner it’s not oriented correctly. It should be oriented so that the long axis of the package is parallel to the long axis of the board. In your picture it actually looks like it is rotated 90°, so that might be your problem right there.

Other observations:
R14 is missing, so that MIDI out won’t work properly.
You can touch up the pins on IC1B

Best,
Andy

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Excellent!

I pluged in via micro usb direct to the wave share board and i have sucess, the “MIOS 32” shows up.

I will investigate the other issues you mention Andy and report back, thank you so much for the input.

Best,

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Also i dont have r10 filled it seems. Its on the BOM so I’ll populate that.

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hrmmm, I populate r14 (and r10, I am assembling two boards and it was missing on one) but still not working.

I also tuched up the pins on IC1B but no luck. Also, i tripple checked all diode orientations and they are all per te silk screen.

Any further sugestions would be appreciated.

Many thanks,

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Let’s see a closeup of that TVS diode. Also you can try to trace the USB pins right to the waveshare board, or even the STM chip.
R30 to PA11
R31 to PA12

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Thanks again Andy,

I have checked and i have continuity between R30 and PA11 and R31 to PA12 on both boards. But no luck.

Are these data pins? Is there something on there i could se with a scope? Worth checking?

Is the TVS didoe diode 01? There is a close up attached of D1 and D2,D3

Lastly just to make tripple sure i tested with a different USB cable, the one from my printer. I assume if I can print with it, it must be transmitting data…

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Hi Ed, you’ll find TVS1 on the back of the board.

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Ohh, yeah right, you mean the one labled TVS1 🤣

I have it rotated 90deg dont I?

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I corrected the orientation and tested again but still not showing up. I hope I haven’t compromised some other component(s) with having the TVS wired in wrong…?

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90° clockwise or anticlockwise? Check the build video for the right orientation.
You could have cold joints on the USB socket, so look closer there and consider tracing the USB pins on a cable or the inside of a connector to R30(D-)/R31(D+).

It would be pretty unlikely but you could have a missing trace from the header to the STM chip (pins 70/71).

Good luck!

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I sacrificed a USB cable to the cable gods and found that I had created a short between the USB + and - on one of the boards when I repositioned the TVS diode (when I flooded it with solder and flicked it off, I managed to get some solder on the USB socket pins.

So that mystery is solved! One board now reading MIOS 32.

I can’t see the orientation of the TVS now as the markings are now not visable probably due to the heat when I unsolderes/reordered. I’m pretty sure I rotated it 90deg clockwise.

Other board still not working but I will investigate further. Just wanted to update that I got one board working for now so half way there!

Thanks again for the help Andy. Very much appreciated!