Electronics > Beginners
Decoding with An O-Scope
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JAndrew:
I'm quite new when it comes to decoding digital signals and I am trying to use my Rigol DS2072 to decode a signal.

I believe the signal follows the RS232 protocol, but the baud rate looks to be 55,550 baud which is an oddball baud.

I've been trying to get my decoding feature to work on the O-Scope but its been a bit of a bugger to try and figure out  some of the settings such as how many bits, whether there is a parity bit, or how many stop bits. I have no information on camera the signal is being sent to, or the unit that the is sending the signal.

Any help would be appreciated. I've attached a screen shot from the O-Scope




Thanks,

Jay
ataradov:
Do you expect it to be RS232, or UART? Where does this signal come from? Normally UART has idle level high. And RS232 has higher voltage levels.

It is hard to tell from this capture, but it looks like there is also quite a bit of variability in the bit timing.

Try to zoom in close on the first suspected byte and do the decode by hand. Assuming it is 8N1 format, the data appears to be malformed.
JAndrew:
The plug is a Type Micro-B, I was playing with it a few minutes ago, the image above was generate when the probe was connected to the Data + line, I have subsequently found that if I connect the probed to the Data - I get a far clearer signal. Same signal, just a the picture perfect square waves you'd expect.

This is what throws me off. As you said UART idles High, this idles low. This is the full waveform and it repeats. I suspect the micro controller is querying the camera to see if it's there.

I'll see if I can't maybe decode it by hand. Still working on learning how to decode binary.

Thanks,

Jay
ataradov:
Is it actually the same signal? Put them both on two different channels and compare.

How often is this sent?

If you provide more information on the actual devices you are probing, we may be able to help you better.
JAndrew:
I'll get some more screen shots with the set up and what I am trying to do tomorrow. I appreciate the help!

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