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Trouble with ttl to usb interface

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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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    I'm not a RIoTboard user but I've done a lot of UART.

     

    Here are a few things I'd try.  First, make sure the USB UART dongle is working by itself.  Unplug it from the RIoTboard and connect the RX and TX bits to each other.  Then start up your terminal emulator and see if it echoes the characters you type to the screen.

     

    If this doesn't work, you either have a bad USB UART dongle or you don't have the serial configuration right.  Specifically, be sure that flow control is OFF or NONE since you only have RX and TX.

     

    Once the USB UART echo works, make sure you have the correct serial config for RIoTboard.  You obviously have the Baud rate correct or you wouldn't be seeing the boot trace.  I think the correct setting is 115200N8 so make sure you have parity turned OFF, 8 bits per byte, and flow control OFF.

     

    Otherwise, as Gary says you probably need a 'scope to see the signal from USB UART TX to RIoTboard RX.

     

    Hope this helps!

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  • 0

    I'm not a RIoTboard user but I've done a lot of UART.

     

    Here are a few things I'd try.  First, make sure the USB UART dongle is working by itself.  Unplug it from the RIoTboard and connect the RX and TX bits to each other.  Then start up your terminal emulator and see if it echoes the characters you type to the screen.

     

    If this doesn't work, you either have a bad USB UART dongle or you don't have the serial configuration right.  Specifically, be sure that flow control is OFF or NONE since you only have RX and TX.

     

    Once the USB UART echo works, make sure you have the correct serial config for RIoTboard.  You obviously have the Baud rate correct or you wouldn't be seeing the boot trace.  I think the correct setting is 115200N8 so make sure you have parity turned OFF, 8 bits per byte, and flow control OFF.

     

    Otherwise, as Gary says you probably need a 'scope to see the signal from USB UART TX to RIoTboard RX.

     

    Hope this helps!

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