I am having problems with the TLC4950 PWM shield from SparkFun. Occasionally it will fire all channels for one of my 50 millisecond cycles (change values as most, every 50 milliseconds).
I am using my setup to control my Christmas light display. My setup includes an Arduino UNO, the Sparkfun PWM shield, a Rugged Audio Shield to play the music, and the Arduino Wireless shield (using the micro SD card slot only, no wireless option connected).
I use the SD card to store the sequence of lights to turn on and off. The Rugged Audio Shield is mostly self contained in that I only have to tell it to start playing a song on its own SD card, and it takes care of it. The Arduino doesn't have to drive it. My lights have a cycle of 50 milliseconds (time between when lights might turn off or on). I am not doing any dimming the lights, either on or off. The flashes may occur as often as every 10 seconds (keeping in mind that I am switching states every 50 milliseconds) and appear to last for a full cycle. The time between flashes is often longer.
The flashes seem to occur at roughly the same spot in my sequence, though I have been able to change that by inserting additional delays (which makes the sequence unusable). I have observed the flashes during periods where the shield was in a steady state - meaning the light values did not change between cycles though I did resend the same data. I observed this when there was only a single channel that was on. Getting the data from the PWM shield showed what I had sent, and not what was on.
I am driving relays (both mechanical and SSRs) from the shield. It doesn't make a difference which one I am using.
Any ideas what the problem might be? Is the PWM shield defective?
Thanks for the help.