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Circuit for progamming uLCD-32PT

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  • Circuit for progamming uLCD-32PT

    I recently received a uLCD-32PT-GFX and a uUSB-CE5. Unfortunately the uUSB-CE5 was defective and I'm trying to figure out how to program the LCD with a standard USB-Serial converter that has a D9 connector. I've gotten as far as wiring up the LCD to a power supply (with a common ground for the serial connection). I can power up the display and reset it but I cannot get 4D Workshop to communicate with the device. The serial port looks to be working fine: I can put an LED on the TX and it blinks when I try to communicate with the LCD. (As far as I can tell RX and TX are all that are required from the serial connector.) I'm wiring TX and RX straight into the LCD, so I'm not sure if level conversion needs to be done (if so, hopefully I haven't damaged the LCD). I've seen other posts regarding confusion over which pin is RX vs TX but every time I try a new configuration, I swap the lines just to be sure. And I started with the standard 9600-8-N-1 baud settings but have tried numerous others. Other than that I'm all out of ideas.

    A (crude) schematic of the circuit is attached.

    Thanks,
    John Attached files

  • #2


    you cant - should not do that - D9 can have upto +12/-12V and are inverted to the standard - you need a MAX232 type IC in circuit to level shift

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    • #3


      I was afraid of that, actually. My assumption (incorrectly) was that the uUSB-CE5 was a true USB to serial converter (i.e. +/- 12v) when, in reality, it converts to a TTL signal. The datasheet does state "RX and TX signals are both 3.3v and 5v tolerant", I just missed that part.
      I should have a MAX232 or similar in the parts bin so I'll give that a try. Hopefully I didn't fry the RX/TX ports on the LCD.
      Can anyone confirm that the COM port settings are indeed 9600-8-N-1?

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