Guys I have some questions regarding the Texas Instruments TLC5940 16 channel PWM. I see this is mainly for Output but I am in need of reading that output's voltage value to basically test continuity between each channel.
Basically here is my situation I am trying to accomplish ..
I need to test cables that I am building to make sure the "pin" out's have been poked correctly. so for instance a USB cable which is 4 pins, 8 pins total counting both sides. I need to make a test fixture that I can plug the cable into which will test each pin on each side for continuity and let me know if theirs a OPEN short or not. Now this will start small but we have cables that are much more complex which will require much more pin outs. for instance 255 total nodes about 128 wires to test in some of our harnesses.
What would be a good solution for handling this type of thing? Any help would greatly be appreciated.
128 outputs, 128 inputs with pullup resistors.
Read all inputs, make sure none shorted to Gnd/shield/backshell.
Drive 1 output low, read all inputs and check that only the correct one is going low.
Confirms continuity and no shorts to other pins.
Bank of shift out registers and shift in registers, all daisy chained.
I would use open-drain shift out registers to sink current from the pullup resistor, won’t be damaged by shorts.
Actually, this board I carry has 96 outputs, so you'd be halfway there. I could design a similar mating board with shift in registers.
I don't think the TLC5940 is useful for this. It's a current sink, not a voltage source.
You don't say if you need to test each wire individually, all at once. Are you only interested in OPEN wires or do you also need to check if the pins are mixed up?
An Arduino can easily do this sort of thing with some add-on shift registers like the 74HC595 to expand the number of pins.