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PIC Output Driving Voltage

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  • PIC Output Driving Voltage

    Would a PIC (12LF1822) which is a 3 volt i.c., be able to debug to a serial 5 volt LCD? Enough reference to high/low?
    Secondly, the 'bit' assigned in the debug define, for example using RA2 I/O, does this mean using 2 as the bit or 3 as the designated bit?

  • #2
    Three volts might be enough for the LCD to register as a binary "1", you'll have to look at the data sheet.. If you are receiving signals from the LCD at 5 volts, you will have to use a voltage divider. Pins cannot be driven more than 0.5 volts above VDD. There is an internal diode that will try to short anything above that, and too much current and it'll fry the PIC. It may also cause the LCD some harm.
    We can crack this cotton PIC'n thang!

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    • #3
      Nothing going to the PIC from 5 volts. Just confused about the name (bit) for the debug out rather than calling it a pin. So if I'm debugging out RA2 on this pic, is it considered bit 2 or bit 3 (RA-0,1,2)

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      • #4
        I think you're now asking about using PBP commands to do something I just bang out manually. Don't think I can help you there.
        We can crack this cotton PIC'n thang!

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        • #5
          It's called a bit because it actually is a bit, in the register called PORTx. That register is then connected to the actual pin via the tristate buffers than is controlled via the TRISx register. If you
          Code:
          DEFINE DEBUG_REG PORTA
          DEFINE DEBUG_BIT 2
          The debug output will be on PORTA.2 or RA2 if you like (which is the 3rd bit in that register since you start counting at 0).

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          • #6
            Thanks Henrik. Then in that case, using RA2, the PIC's I/O is not capable, at 3 volts to trigger the 5 volt driven, serial display.

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            • #7
              You could use a transistor or 2N7000 and invert the output. Tie the transistor to 5 volts with a pull up resistor.
              We can crack this cotton PIC'n thang!

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              • #8
                Yeah, that was my thought

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