PIC32 needs a filter on the ICSP/power supply wires

Discussion in 'Embedded Systems and Microcontrollers' started by takao21203, Aug 6, 2014.

  1. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
    3,577
    463
    There is too much noise on the LED matrixx board, the PIC runs at 80 MHz internally, powered it up a few days ago, and each time I moved my hand near the ICSP pins or the orange wires, the PIC actually stopped (LED stops blinking).

    One morning I came up with the weird idea to wrap a shielding wire around the 5 ICSP wires (2 also for power supply via 2 LED from 5v), short it together, and ground that.

    It worked instantly, even touching the PIC32 anywhere does not cause any reaction at all anymore. maybe the beads are not required, did not test.

    The 22uH inductor in the Vcc line is required too, just the shielding alone or the inductor dont do the job. Tried that, removed it, same problem again.

    Yes I know the PIC32 board looks messy, its very old, was a gift I received, see date stamp on the PCB, actually the first TQFP chip I ever soldered.

    It has 512K FLASH and 128K RAM, and 80 MHz, not a bad IC for that time.
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    How have you wired the MCLR/Vpp wire? Sounds like you might have left it floating?
     
  3. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
    3,577
    463
    Set as IO, also tested, no result to put a 4.7k resistor.

    It would still react even with the filter.
     
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