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No output or invalid output on a 74HC595 shift register

I have a PIC18F2550 microcontroller on one board with three daisy chained 74HC595 chips. These are driving 7-segment displays and everything is working fine. 7-segment displays are connected with a cable. The thing is connected to my computer with USB. This is where it draws it power.

Then I added an another 74HC595 on a separate board to drive LEDs. It's not daisy chained with the other chips, but connected to separate pins on the microcontroller. These LEDs are sometimes on and sometimes off, might change state once when I try set them in different states from software, or not. Usually all of those LEDs end up being all on or all off. 7-segment displays continue to work as expected.

Here is the date sheet of 74HC595:http://www.componentschip.com/details/Texas-Instruments/74HC595D.html

Then I added yet another 74HC595 on yet another board to drive a separate 7-segment display and connected it to separate set of pins on the micro. It functions the same way as the other separate board.

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Topic - No output or invalid output on a 74HC595 shift register - makiyang614@gmail.com 20:59:57 07/03/17 (1)


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