Issues upgrading to NHD-0220D3Z-V3

Comments

7 comments

  • Michael_L

    It sounds like it is something to do with the timing.  Not the baud rate of the rs232 itself, but rather the timing between writes/commands.  Can you try adding a delay between writes?

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  • M_DeVries

    I tried delays of 1, 2, 5, 10, 20, 50 & 100 ms between each write with no luck on the -V3 display.  The Rev 1.0 display was successful regardless of the delay length.

    I used my DMM and measured a few pins on the connector.  Because I am using RS232, I don't need to use pins 5, 7 or 8 on the display's connector.  These pins are connected to my micro, which is set-up to drive these pins as outputs with a low signal (so they are non-floating).  When the display is not connected, I measure 0V at each of these pins on my board.  When I connect the display, pin 5 goes up to ~0.3V and pins 7 & 8 drive up to 4.9V.  If I take pin 8 (the data line) and directly connect it to ground (rather than using the low output of my micro), the -V3 display functions as expected with no need for delays between my commands.

    The best I can tell, is that even though R1 and R2 are open (thus indicating RS232 in use), the -V3 display will still listen to the SPI/I2C data line if it does not have a hard short to ground.  The Rev 1.0 display shows similar voltages on pins 5, 7 & 8, but seems to ignore pin 8 data when in RS232 mode.

    It isn't going to be easy for me to modify my PCBs to hard short pin 8 to ground, so any other ideas to get RS232 working would be appreciated.

    Thanks,
    Matt

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  • Michael_L

    I have just tested that display to confirm operation with only the use of 3 pins, without any other pins needing to be grounded.  The 3 pins I used were pins 1-3, RX, VSS, VDD.  Using only these 3 pins, the display was fully functional.  We have never seen this issue before where that pin needs to be grounded in order for the RS232 to work.  Do you have some connection to these pins?  Or are they completely disconnected from any other devices/circuitry as they should be?

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  • M_DeVries

    The other pins are connected to my micro, but I am not doing anything with them - I am not attempting to send or read any data from those pins.  I don't think that I've said before that my micro runs at 3.3V, so I have a bidirectional voltage level translator between my micro and the display.  It is a TI chip, part number is TXB0108.  The Rev 1.0 display works just fine with this setup, but the -V3 display does not.

    .. are they completely disconnected from any other devices/circuitry as they should be?

    I am little surprised by this.  No where in your datasheet does it indicate that these pins need to be disconnected, let alone fully disconnected from everything.  Also, it is generally not good electrical engineering practice to have floating inputs, even if they are unusued, so connecting them to ground or +VDD is often considered a best practice.

    I made a test cable that only had pins 1, 2 & 3 connected and no luck, still getting the character stream.  Exact same cable on the Rev 1.0 display works just as you describe.  I'm using a 14-way ribbon cable with IDC connectors and it is about 6" long.  To make my test cable, I just clipped wires 4-14 in the middle and left them floating.

    Looking at the display board, the silk screen on the board itself says 2002D3 VER 1.1, but the sticker is for the NHD-0220D3Z-NSW-BBW-V3.  What I believe is a lot number above the model number is 112680-11-03-30.

    -Matt

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  • Michael_L

    Do you have another V3 display you could try?  As I mentioned, I tested this display without the need to ground any additional pins and it worked properly.
    If you do have other V3 versions you can try, please confirm if these work correctly or if they are experiencing this same issue.
    If not, would you be willing to purchase another sample to test?

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  • M_DeVries

    I have 3 different -V3 displays and all of them behave the same way.  Is the 112680-11-03-30 a lot code?  If so, does the display you are testing with from that same lot?

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  • Michael_L

    It is a lot code, and the display I was testing is 112680-11-03-23.  Please email us at nhtech@newhavendisplay.com if you would like to submit an RMA form.

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