Driving multiple 74hc595's running at 5V (works reliably now)
RobotWorkshop
Posts: 2,307
I made a nice LED display for one of my latest robot projects using a set of four 74HC595 chips to drive them. One of the 595 chips is located on the Propeller Proto board and the other three are remotely located on the main LED board. When I finally had everything wired up with multiple 74HC595's (running at 5V) the LED's would often display garbage. When I was just running one it worked perfectly. After some testing it appeared to be an issue with the prop trying to drive all the latch and clock lines directly (I have a resistor between the prop pins and the 595. The Serial data wasn't a problem since that was only going to one chip.
My fix was to use a 74HC14 to buffer the latch and clock lines. I had one on my board already to use one of the inverters for the reset circuit. Five of the inverters were unused. So, I used four of the available inverters 2 sets of 2 in order to buffer those signals before going to my remote display. Now the display is working exactly as expected.
Robert
My fix was to use a 74HC14 to buffer the latch and clock lines. I had one on my board already to use one of the inverters for the reset circuit. Five of the inverters were unused. So, I used four of the available inverters 2 sets of 2 in order to buffer those signals before going to my remote display. Now the display is working exactly as expected.
Robert