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Trouble with ttl to usb interface

Former Member

Hey guys, riotboard noob here!  A local computer store had a USB to TTL serial cable based on the PL2303 chip and I can see the boot information through screen and minicom as my riotboard is booting up so that's working just fine.  However, when it comes to the prompt where I can press any key to interrupt the boot sequence, nothing works.  Neither keypresses on the host computer (Ubuntu Linux) or an attached usb keyboard will interrupt the 3 second timer.  What am I doing wrong?  I apologize in advance if this is a painfully obvious problem.  I'm really stumped, though!

 

Background: I purchased the 7" LCD display and connector board for my riotboard.  I'm following the documentation where it instructs me to interrupt the boot sequence so I can enter the appropriate parameters to enable the screen.

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  • 0

    Sorry you did not specify the O/S you used. This sounds a bit more software related. Did you check your connections? Please look at @Debian on RIoTboard - After basic install, adding a GUI Desktop and other usefull stuff

  • 0 in reply to clem57

    I don't think this is software related. I've used minicom on PCs, Raspberry Pi, ODROID-C1, and other SBCs with no problems and I've used screen on PCs with no problems. Its

    also unlikely that minicom and screen would have the exact same problem.

     

    Rich, after checking out the riotboard and USB/TTL converter information from what I see they should be connected like this:

     

    USB/TTL                           riotboard pin #

     

    red wire                             not connected

    white wire  (input)               1  UART2_TXD  (output, this one must be correct for you to see the boot information coming from the riotboard)

    green wire  (output)            2  UART2_RXD (input)

    black wire                         3  GND

     

    If this is how you have it wired then there must be a problem with the USB/TTL converter output, or the riotboard UART2 RXD input. This could be anything from bad IC pins on

    either one (nothing you can do), bad solder connections to the IC pins on either one or the connector on the riotboard or the wires on the USB/TTL converter (may be fixable if you

    can solder), problems with the PCB on either one (probably nothing you can do), or the USB/TTL converter green and black wires are connected to the wrong place (swapped)

    although it probably wouldn't work at all because there would be no good ground reference between them.

     

    If you have a digital multimeter you could verify that there is 5V between the red and black wires on the USB/TTL converter when it is plugged into a USB port. This would at

    least tell you that the USB/TTL converter is probably wired properly. Just about anything else would require an oscilloscope to trace out the problem.

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  • 0 in reply to clem57

    I don't think this is software related. I've used minicom on PCs, Raspberry Pi, ODROID-C1, and other SBCs with no problems and I've used screen on PCs with no problems. Its

    also unlikely that minicom and screen would have the exact same problem.

     

    Rich, after checking out the riotboard and USB/TTL converter information from what I see they should be connected like this:

     

    USB/TTL                           riotboard pin #

     

    red wire                             not connected

    white wire  (input)               1  UART2_TXD  (output, this one must be correct for you to see the boot information coming from the riotboard)

    green wire  (output)            2  UART2_RXD (input)

    black wire                         3  GND

     

    If this is how you have it wired then there must be a problem with the USB/TTL converter output, or the riotboard UART2 RXD input. This could be anything from bad IC pins on

    either one (nothing you can do), bad solder connections to the IC pins on either one or the connector on the riotboard or the wires on the USB/TTL converter (may be fixable if you

    can solder), problems with the PCB on either one (probably nothing you can do), or the USB/TTL converter green and black wires are connected to the wrong place (swapped)

    although it probably wouldn't work at all because there would be no good ground reference between them.

     

    If you have a digital multimeter you could verify that there is 5V between the red and black wires on the USB/TTL converter when it is plugged into a USB port. This would at

    least tell you that the USB/TTL converter is probably wired properly. Just about anything else would require an oscilloscope to trace out the problem.

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