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DM365 USB problem: desktop vs battery powered

Michael16400
Intellectual 515 points


Hello,

I have been looking for hours on an answer but could not find one. Here is my question:

I have a custom DM365 board that has been tested and is working fine with Linux, etc.

Until now, I have been using a micro-B USB cable connected to a desktop PC to power and communicate with the board and I had no problems. I tried using a micro-A USB and same result, the circuit is on and Linux is booting.

Now here is where I have a problem: when using a USB battery (for example the New Trent), the circuit is ON (DM365 is powered as usual) but Linux is not booting. I don't see anything on the serial line: no UBL, bootloader or Linux. Simply blank. Usually there should be a LED switching on (I programmed that into my code) but here nothing...

Where is the problem? If the program is not booting, is there a miscommunication on the USB line? The only difference I see between the USB coming from the desktop and USB coming from the battery is on the USB_P / USB_N or USB_ID lines. The battery probably does not have these 3 lines.

I have attached the schematics of my circuit (DM365 <-> USB).

Please let me know what you think.

Thanks!

Mike

 

5556.dm365.pdf

  • 0
    Intellectual 515 points

    Alright, so the circuit was indeed booting correctly but the problem came in the RS232 line transmission... It seems that due to a difference in the ground signal between the desktop PC and the battery, the RS232 serial line is not on the same level and therefore there is nothing, no serial message for debugging.

  • 0 in reply to Michael16400
    Intellectual 515 points

    So I still have the problem, please HELP!

    The DM365 boots successfully when connected through USB to a desktop computer however it fails when using a 5V USB battery. I found a way to make it work: connect the GND signal to the GND of the desktop (i.e. the earth). The circuit does not work when using the battery ground but does when using the earth ground.

    PLEASE, does anybody know what is the simplest fix for the circuit so that it can rely on the battery GND only?