@Juraj I can share my issue and solution using an M5Core3SE and a Win11 computer.

When I connected the M5 to the USB-A port on the PC using a USB-A to USB-C cable, I got power, but no COM ports.

When I connected the M5 to the USB-C port on the PC (using a USB-C to USB-C cable), BOOM: COM port.

I haven't dug into it to see particularly why (best guess right now is the M5 connection uses both the legacy USB 2.0 connection as well as the SuperSpeed connection: one for the terminal and one for the M5 program data stream?)

Hope this helps.

Sharing issues we've had with the hardware (problems that turned out to be due to the physical module).

• 4-Relay modules (U097). Several modules in different applications had relays that "stuck" off. The LED came on, but the relay did not close. Desoldering them from the board confirmed they were not functional, and a teardown confirmed that they could work. Our solution was to replace the relays with TE equivalents (T77S1D3-05). The most recent relay modules haven't exhibited this problem so far.
• DAC2 modules (U012-B). Two of three modules are dead. Both seem to be having problems with the boost converter (provides 12V for the DAC 10V range). Output of one boost is ~5V, no switching at the SW pin. Other boost gets really warm. Analysis ongoing to what and why they failed. Anyone have insight here?

Anyone have other issues (and hopefully fixes)?

Update on DAC module: found probable root cause from within my system setup.

Failure point on the module is the +5V input - only a few ohms vs GND. I found the +5Vdc supply transient of -4V relative to GND for 200µs. Most ICs don't do well with anything below -0.3V relative to GND.

(the transient is caused by design depending on a great deal of Grove wiring as a GND path, combined with relatively high voltage/current on other rails in the system. One solution is redesign for low-ohm, low impedance GNDs)

Sharing issues we've had with the hardware (problems that turned out to be due to the physical module).

• 4-Relay modules (U097). Several modules in different applications had relays that "stuck" off. The LED came on, but the relay did not close. Desoldering them from the board confirmed they were not functional, and a teardown confirmed that they could work. Our solution was to replace the relays with TE equivalents (T77S1D3-05). The most recent relay modules haven't exhibited this problem so far.
• DAC2 modules (U012-B). Two of three modules are dead. Both seem to be having problems with the boost converter (provides 12V for the DAC 10V range). Output of one boost is ~5V, no switching at the SW pin. Other boost gets really warm. Analysis ongoing to what and why they failed. Anyone have insight here?

Anyone have other issues (and hopefully fixes)?

I'm apparently hard on these modules?

There have been a couple of 4-Relay modules (U097) that I have found where the relay sticks off. We was able to find a drop-in replacement (TE T77S1D3-05), but still don't know why the original relays were sticking (I did a tear-down analysis, but haven't gotten authorization to send it through the x-ray machine yet).

Now I have had two DAC2 modules (U012-B) fail. On one the boost just ... isn't switching anymore: 4.88V at the output (what you'd expect after a single diode drop). The other is still under analysis, but there is no boost output and the IC gets hot

All this to say: is there a place where the Bill of Materials for M5 stuff is accessible? The schematics and some datasheets are available at https://docs.m5stack.com/. However, the schematic is often lacking relevant part specifications or part numbers.

At the least it would be useful to figure out WHY the modules are giving up the ghost (am I demanding too much output current? Do I need to layer additional protections?). Being able to replace parts may sometimes be helpful too.

@robski I tried multiple cables. Every USB-A to USB-C cable failed, some of which I had used in the past for data transfer. I am only using 1 cable: USB-C to USB-C

@ajb2k3 To clarify: are you saying that somewhere in the Core3SE documentation it says that USB-A is power only? Could you link that or point me to it? I clearly need to dig into the hardware a bit more :)

@Juraj I can share my issue and solution using an M5Core3SE and a Win11 computer.

When I connected the M5 to the USB-A port on the PC using a USB-A to USB-C cable, I got power, but no COM ports.

When I connected the M5 to the USB-C port on the PC (using a USB-C to USB-C cable), BOOM: COM port.

I haven't dug into it to see particularly why (best guess right now is the M5 connection uses both the legacy USB 2.0 connection as well as the SuperSpeed connection: one for the terminal and one for the M5 program data stream?)

Hope this helps.

We have been exploring the M5Stack to standardize on for automated board-level testing, and have three sets of fixtures designed around the modular scalable M5Stack Core2 and CoreS3. The fixtures include the U097 4-relay module connected through the Groove port, or through a U040-B I2C expansion hub.

Unfortunately, we have experienced multiple failures of the U097, characterized by relay 1 not engaging wen energized. This has occurred with one U097 out-of-box and two during fixture verification. Root-cause analysis of the U097 seems to indicate mechanical sticking of the LCSC 932-5VDC-SL-AH relay: if the relay is removed and the coil directly energized there is still no continuity between the switch pins, but if the relay outer case is removed it functions as expected.

The relays are being used to switch signals well within their capabilities (5V, 5-50mW).

Is this a known issue? I saw another user who had an "old" and "new" U097, where the old one worked fine and the new one did not. Has something changed?