3 Replies Latest reply on Mar 27, 2014 1:09 PM by JPMontero_Intel

    PWM pins and Shift Register Clocks Boggus Interaction

    janunezc

      Hi,

       

      I have been running some experiments with Shift Register (74HC595) and the Galileo board, and got stuck with a behavior that is quite weird.

       

      I put up some breadboard wiring to have a shift Register operate a 7 segment display (or a led sequence)

       

      Fritzing Diagram Here: https://github.com/janunezc/ARDUINO/blob/master/demo_shift_register/74HC595_7SEGs%20-%20Single.fzz?raw=true

       

      Basic Code Here: https://github.com/janunezc/ARDUINO/blob/master/demo_shift_register/shift_register_leds/shift_register_leds.ino

       

      What this does is basically fill the shift register up to 6 bits forming a zero in the 7 segment display.

       

      But, when I use pin 11~ of the Galileo board as Shift Clock (connected to pin 11 in the 74HC595) then it esporadically makes two shifts instead of just one when the Shift function is called.

       

      After a lot of troubleshooting I moved to pin 8 which is not PWM, and the misbehavior ceased.

       

      The question is: is there any consideration we have to officially take in regards of PWM pins to control digital clock signals there? I though using digitalWrite would be good enough, to make those pins behave the same as non PWM pins... Analo