Can't connect Mega 2560 Pro on Ubuntu; not brltty problem

Hardware
1

Hello,

I'm trying to connect some Mega 2560 Pro (Embed) clone boards to my Ubuntu 22.04 system. I swear that this was working less than two months ago.

I don't think that this is the 'brltty' problem, because I've removed brltty.

Now, when I connect the board to the USB port, nothing at all shows up in dmesg. The board, itself, seems to be okay, and running the blink program.

I've installed the CH34* package, according to the instructions at How to Install CH340 Drivers - SparkFun Learn. However, something's still not right with this. The drivers show up with:

$ lsmod | grep ch34
ch34x                  24576  0
usbserial              69632  1 ch34x
$

But, they disapear on reboot, and I have to manually load them again each time. Even after the drivers show up in dmesg, the board doesn't show up when I disconnect and connect it.

I've tried different cables, with basically the same results, so I don't think it's the cable.

I've had some strange experiences with the boards, that maybe could have affected them. With one cable, the +5V regulator (the one closest to the edge of the board) got so hot in less than 10 seconds that it burnt me. I get this result intermittently with different cables and different boards, and wonder if it could have damaged the CH341 chip on the board.

Any suggestions? Any diagnostics I could run? Thanks for any suggestions.

-Kevin

2

Not sure what the problem is but check the cables to be sure they are correct. Also what type of USB port are you connecting to. What type of connector is on the board. Three things that will make the regulator, reversed polarity, overloads, or improperly bypassed and it is oscillation. An annotated schematic and links to the technical information on the boards would help.

3

No help but Linux comes with the driver; there should not be a need to install. On my 32-bit linux system

  1. After a reboot (CH341 disconnected), lsmod does not show the CH341.
  2. After connecting the CH341, lsmod shows the driver.

Because your dmesg output does not show any reaction, my suspicion is cable, broken USB port on the PC or broken Mega2560 Pro.

1 Like
4

@sterretje and @gilshultz , thanks for replying.

I don't think it's the USB port or the cables:

  • I can use the same cable and USB port to read and write a MP3 player
  • I can use the USB port and a different cable to connect to an Arduino Nano.
  • I can use the USB port to read and write a USB memory stick.

Occasionally, the 5V regulator on the two Mega 2560s gets really hot. Not every time, but at least 1 out of 3 times. I can't determine what causes this.

I've rebooted and tried to connect. The Nano shows up correctly in dmesg, but both of the two Mega 2560s don't show any activity in dmesg when connected.

Boy, this is weird.

-Kevin

5

This might be caused by a short or external circuitry connected to the Arduino board drawing excessive current.

Make sure the board is not sitting on anything conductive that could short the contacts on the bottom of the board. Inspect the board carefully on both sides to make sure there isn't any conductive debris (e.g., strands of wire or component leads) on the board or on the surface the board is sitting on.

If you have a shield or any external circuitry or components connected to your Arduino board, try this experiment:

  1. Disconnect the USB cable of the Arduino board from your computer.
  2. Disconnect any shields, modules, external circuitry, etc. from your board.
  3. Connect the Arduino board to your computer with a USB cable.

Now check to see if the problem still occurs.

This experiment will determine whether the problem was caused by the external circuitry. If so, you can then focus your attention on identifying the specific problem with the circuit and resolving it.

1 Like
6

@ptillisch , thanks for your thoughts.

I don't think that there's anything shorting both boards, intermittently. One of the Mega 2560s just has the headers soldered in. The other one has had nothing done to it. It's just the way it arrived from the manufacturer. No headers or anything else connected. I've tested both on a wooden desk surface; no conductive materials. I've done your 1 and 3 steps; can't do 2 because nothing's connected. No change, no joy.

Thanks, again.

-Kevin

7

The problem is probably caused by the boards having suffered permanent physical damage. I recommend you carefully review what you were doing with the boards the last time it was in a working state. You may be able to identify the cause of the damage and in this way profit from the mishap by gaining knowledge that will allow you to avoid subjecting boards to the same conditions in the future.

Unless you have the right tools on hand and the skills to use those tools, repair of the boards will not be feasible. I suggest you attach a note to the damaged board describing what is wrong with it and put it in your electronics salvage bin. Then purchase a replacement board.

8

Finally getting back to this after a month.

I think I've sorted out the 'no USB communications.' I think I had more than one 'charging-only' USB micro cables. When I finally used a cable that work with reading my USB MP3 player, it also worked correctly with the Mega 2560. I now see information on the Mega in dmesg when I connect it.

I'm still experiencing the intermittent overheating problem, though. I've got a brand new, fresh from the factory "MEGA 2560 PRO (EMBED)" with nothing soldered it, no headers attached. When I connect it using my good USB micro cable, about 4 out of 5 times, it seems to run the blink program for about 20 seconds, then stops. When I disconnect it and touch it, the 5V regulator is hot enough to burn me. The other time, it runs the blink program fine, and the 5V regulator doesn't get noticeably hot or even warm. I've tried it with two different USB micro cables, with the same intermittent results. The board is suspended in the air; nothing touching it.

I'm baffled by this. Any thoughts or suggestions?

-Kevin