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Grand Central USB stopped working
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Grand Central USB stopped working

by evgbrowns on Thu Apr 02, 2020 10:34 pm

I have a GCM4 that was working fine (after a little help with power and ground - thanks adafruit_support_bill), but all of a sudden the USB connection no longer works. On power up the big LED goes green, the power green is on, and the yellow LED is steady and red off. I no longer get a CIRCUITPY drive (on my connected Raspberry Pi), and Mu says there's no Adafruit device connected. My prototype code.py communicates with the Pi via a UART, and that works fine, Pi sends a command to GCM4 via UART and GCM4 responds as it should. I tried double reset and the big LED went, small red blinking, but no GCM4BOOT drive. lsusb doesn't show the GCM4 (it did before). Same USB cable (and same result with a different cable). Tried plugging into Windows 10 (with USB power - it did power up OK), again no drive shows. Between it working last, I did some rewiring to get a common ground distribution for all my connected hardware, power supplies, and the GCM4 and RP (vs. one-offs), but reverting to the connections before with dedicated ground plus the USB and UART TX/RX same result. Any thoughts on how to recover the USB functionality?

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Re: Grand Central USB stopped working

by dastels on Fri Apr 03, 2020 10:06 am

I have to ask... have you tried other USB cables? You don't say whether you have or whether this is the same cable as you were using before. It's a common enough issue that it's always my first question.

Dave

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Re: Grand Central USB stopped working

by evgbrowns on Fri Apr 03, 2020 12:45 pm

Good question - it was the same cable, which hadn't moved when this started. I swapped cables with the same result. This morning I took the cable and verified it worked separately. I've also tried multiple ports on the powered hub connected to the Pi (including ones working for other devices). All the same - no CIRCUITPY drive and no Mu Serial connect, but the code.py appears to be running and responding to the UART communication.

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Re: Grand Central USB stopped working

by dastels on Fri Apr 03, 2020 1:10 pm

I'm stumped, but I reached out to see if I can find someone who might have something to offer.

One thought is going in via the debug connector and reflash the bootloader & such. But I suggest waiting a bit to see if anyone has an easier fix.

DAve

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Re: Grand Central USB stopped working

by dastels on Fri Apr 03, 2020 8:13 pm

There's some wondering about the rewiring you did. I'm wondering if that's related.

Dave

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Re: Grand Central USB stopped working

by adafruit_support_bill on Fri Apr 03, 2020 8:25 pm

I believe this is the thread regarding what seemed to be grounding issues between the M4 and the Pi: viewtopic.php?f=63&t=152862&p=804628#p804628

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Re: Grand Central USB stopped working

by evgbrowns on Fri Apr 03, 2020 9:50 pm

Per the earlier thread, I installed a direct ground connection between the Pi and the GCM4, which stopped the “device removed improperly” Pi messages on the CIRCUITPY. I have several LED strips, servos and solenoids and associated driver boards, which were all wired somewhat haphazardly (lots of wires connected with electrical tape). So, I got a couple power distribution strips (one +5 for the servos and LEDs and one +7.5 for the medium solenoids) and connected all the miscellaneous hardware to them, connected their grounds together, and connected the Pi and GCM4 grounds to the power strip grounds. That’s when the USB stopped working. I had removed the direct ground because they were both connected to the grounds of the power strips, but when I saw what was (not) going on, I tried several combinations including putting the direct Pi-GCM4 ground connect back in addition, removing the power strip ground connections and only having the direct ground connect, and ultimately removing all connections of any kind to the GCM4. I can’t get USB functionality in any configuration.

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Re: Grand Central USB stopped working

by adafruit_support_bill on Sat Apr 04, 2020 7:36 am

When you say "power strip" are you referring to an AC plug-in power strip? Or some sort of a DC power bus?

Some wiring diagrams that show all those connections and what changes you made would be helpful.

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Re: Grand Central USB stopped working

by dastels on Sat Apr 04, 2020 12:30 pm

Have you tried changing the USB port on the Pi, or power cycling it? There's often protection circuitry on USB ports that will shut them down when there's a problem.

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Re: Grand Central USB stopped working

by evgbrowns on Sat Apr 04, 2020 5:14 pm

The "power strip" here is a DC power distribution set. I have tried multiple USB ports on the powered hub that connects the GCM4 to the RPi. Other USB devices on that hub work fine in all ports. Thanks for all your help.
GCM4-RPi Wiring.JPG
Prototype setup with GCM4, RPi, power supplies and other hardware
GCM4-RPi Wiring.JPG (352.88 KiB) Viewed 64 times

Prototype April 4 Wiring.pdf
Wiring list
(226.98 KiB) Downloaded 4 times

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Re: Grand Central USB stopped working

by adafruit_support_bill on Sun Apr 05, 2020 7:04 am

The RasPi schematics for some reason do not show the connections to the jacks. But there is some discussion on the forums indicating that they are not isolated. Not too surprising I suppose since it is a low-cost board.
https://www.raspberrypi.org/forums/view ... hp?t=12008

Is there any particular reason you are powering the Grand Central from a separate supply rather than via USB from the Pi? Try removing all connections from the Grand Central other than power, then measure the voltage between GND on the Grand Central and GND on the Pi.

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Re: Grand Central USB stopped working

by evgbrowns on Sun Apr 05, 2020 1:31 pm

I powered the GCM4 separately when I was working the earlier issue. I did earlier try plugging the GCM4 into my Windows 10 box with just USB and behavior was the same (green solid status, no USB visibility). I just now tried the GCM4 only powered through the powered USB hub connected to the RPi, same.

With all connections removed from the GCM4 other than power and USB, 0 voltage between GCM4 GND and RPi GND. Removing the external power so only connection is USB, I measure 0.4V. With no external power GCM4's +5 reads 4.9 and +3.3 reads 3.3.

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Re: Grand Central USB stopped working

by adafruit_support_bill on Sun Apr 05, 2020 1:33 pm

With all connections removed from the GCM4 other than power and USB,

Remove ALL connections - including the USB. Measure with just power connected to the boards.

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Re: Grand Central USB stopped working

by evgbrowns on Sun Apr 05, 2020 3:28 pm

With only external power to the GCM4 and only power and USB/HDMI connections to RPi, GND to GND is floating (meter bops around, always well under 200mv). I understood the things we looked at before, what were you looking for here?

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Re: Grand Central USB stopped working

by adafruit_support_bill on Sun Apr 05, 2020 4:45 pm

Your system has symptoms consistent with a grounding issue. Your Pi was reporting power issues on the USB port. A substantial difference in ground potential could cause abnormal current flow through the port.

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Please be positive and constructive with your questions and comments.