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pic18f2550 serial communication

Discussion in 'Microcontrollers, Programming and IoT' started by ashwinraj, Jun 11, 2013.

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  1. ashwinraj


    Jun 11, 2013
    hi i am new to pic uc 18f2550. i am using mplab and writing program in assembly language
    problem is when ever i turn off power supply , data in transmitted to hyper terminal (turn off is not instantaneous)
    i used 4MHZ AND 20MHZ CRYSTAL same problem occurred in both cases ,also checked baudrate setting

    check attach for code

    Attached Files:

  2. gorgon


    Jun 6, 2011
    It depends on what you are receiving. If it's only noise(random characters) It could come from how the serial hardware is powered/designed. If it is valid data you need to check out what initiates that when powering down.
    I don't know the PIC in question, but normally PICs has brownout protection that should prevent the processor from going off track.
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Post a schematic of your serial port hardware.

    You could try adding a pullup resistor on the transmitted data pin on the PIC, if the RS-232 driver (or whatever you're using) doesn't have one internally.

    Can you capture the signal on the transmitted data pin from the board to the computer at switch-off?
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