Debugging USART using Saleae logic probe

[Demon]

I must have several obsolete remotes lying around in the basement. What exactly do I want to scavenge out of them? Is it only that clear LED-looking-thing that is necessary?

Robert

[ozarkshermit]

Robert:

Any of the old remotes would probably work to experiment with for a transmitter. They would all have the related protocol for whatever device they were controlling, but that wouldn't matter, if you just want to prove out the method you use to capture the output on the Saleae. Yes, the LED is part of the transmitter.

You need a IR receiver as well. Some folks just use a photo transistor, I would recommend a good IR receiver, since they have additional features built in. I am using a TSSOP 32338, but there are a multitude of receivers available.

Here are a couple of good links on this subject:


http://learn.adafruit.com/ir-sensor

http://www.robotshop.com/blog/en/bui...e-decoder-4254

http://www.pic-tronics.com/IR-Transm...d-Receiver.php

If you want, I can post a couple of screen shots of my results, first a sample of an actual transmission from a TV remote, and then one of the duplicates using a PIC to output the pattern.

Ken

[Demon]

10 years later and I'm still loving my basic Saleae logic probe. It was invaluable to help me figure out what's going on with these encoders.

- noticed jitter on 2nd circuit on chinesium double encoder when I move other shaft,
- spent all day going through my code, turned out the 2nd channel is also dropping pulses.

I can't imagine life without it (top pair at PIC, bottom at encoder pins).




Pulses are inversed because I use a 74HC14 after Bourns debounce to clear up signal.

[richard]

the saleae can just as easily miss pulses as anything else if the sample rate is too low, re's need a high rate i use 12-16 Ms/S to be sure

[Demon]

Nah, I just rechecked with a setting as fast as it goes and the encoder is acting up:

- slight movement of shaft affects other circuit,
- missing pulses on 2nd circuit.

I'll have new EC11 PCBs coming in a week (silkscreen of 1st batch is wrong - D'OH! ), I'll test a few other EC11 double-shafts then.

It's not like I'm lacking tasks and chores to do until then.

[Demon]

It seems the USART analyser (Async Serial) has been updated since I last used it - the formatting has changed a bit.

Again proved invaluable to see if my data was being sent properly.

I love that feature of right-click on the red line of text, so I can quickly switch from Decimal to ASCII.