Author Topic: Rigol DS1054z serial decode problem  (Read 1256 times)

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Offline artelse

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Rigol DS1054z serial decode problem
« on: October 31, 2016, 11:06:10 PM »
Trying out the serial decode option on my Rigol DS1054z and can't figure out why it is not decoding properly. I've set trigger to rs232, baud, etc. , but it seems to treat every pulse as a full frame? See attached screenshot and text file with settings where I send an uppercase U (0x55). As I am just starting to explore this functionality perhaps I need another setting?
 

Offline Fungus

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Re: Rigol DS1054z serial decode problem
« Reply #1 on: November 01, 2016, 12:43:23 AM »
a) Most RS232 signals start high and go low when there's data.

b) Try sending a different byte and see if it's what you expect.
 

Online nctnico

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Re: Rigol DS1054z serial decode problem
« Reply #2 on: November 01, 2016, 01:02:16 AM »
a) Most RS232 signals start high and go low when there's data.
That is on TTL level. On real RS232 you see what is pictured in the screendump (note the v/div setting!). If the OP sets the decoding to 'idle low', not-inverted, -whatever Rigol calls it- it should work.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Fungus

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Re: Rigol DS1054z serial decode problem
« Reply #3 on: November 01, 2016, 01:06:11 AM »
On real RS232 you see what is pictured in the screendump (note the v/div setting!).

I see 2 v/div, 5.3Vp/p.

"Real" RS232 would be +/- 12V.
« Last Edit: November 01, 2016, 01:07:42 AM by Fungus »
 

Online nctnico

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Re: Rigol DS1054z serial decode problem
« Reply #4 on: November 01, 2016, 01:08:42 AM »
Hmm yeah. I'm too used to 3.3V (and less logic).
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online H.O

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Re: Rigol DS1054z serial decode problem
« Reply #5 on: November 01, 2016, 01:10:08 AM »
Except the polarity setting, what's the baudrate?
I see in the settings file that the decoder is set to 2400 baud but the bit-time seems to be WAY to long for tat.
 

Offline artelse

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Re: Rigol DS1054z serial decode problem
« Reply #6 on: November 01, 2016, 01:27:17 AM »
Thanks for the replies! I found the problem, it was the cheap ass Chinese USB - Serial converter.. I swapped it with a decent one et voila all is fine! The problem with the board now also became apparent: a faulty MAX236.
 


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