Hi TI Community:
I am hoping to solicit some ideas; knowing full well this may not be related to anything TI.
I am working with a TM4C129XNCZAD.
I started off using 4 PINs to sequentially light 4 LEDs, one at a time. No two LEDs would ever be On at the same time.
I replaced each LED with a PhotoResistor and then I wired an ADC 'detector' in each of the 4 circuits to measure Voltage.
I was careful to align the "power - on/off" PINs to the ADC channels that were being used on each circuit.
I'm using SS3 and feeding the Sequencer one Channel at a time. I'm using Power from each PIN and using a common ground for each circuit back to the board.
Sequence of Events: Turn On PIN, Detect Voltage using ADC, Turn Off PIN, Rinse / Repeat for each and show all 4 results.
Each individual ADC value changed when I changed the lighting level to each individual PhotoResistor.
It appeared as if each circuit was acting independently.
I covered 3 of the PhotoResistors with 3 layers of tape. Those 3 ADC values dropped to expected levels.
I shined a light on the uncovered PhotoResistor and the ADC value went up as expected.
Then I noticed something odd..
A few of the 'covered' ADC values climbed significantly when I shined a light on the uncovered PhotoResistor.
Those values should have remained constant because they were covered up.
As a control, I shined the light on the 3 covered PhotoResistors and none of the values changed.
This was a check to make sure that light was not bleeding past the covered PhotoResistors. It wasn't.
I'm not sure what to make of the uncovered PhotoResistor causing an increase in values on the covered PhotoResistors.
This does not quite add up to me. If anyone has any ideas to share, I would really appreciate it.
Thank you.
Rick
