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2205MSO SPI decoding not working at high speed (2Mhz)

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2205MSO SPI decoding not working at high speed (2Mhz)

Postby bunjatec » Tue Jun 19, 2012 2:22 pm

I have managed to get the SPI decoding to work with a clock at 200khz, but at 2 Mhz the decoding seems to have missed the packet.

it recognises the start, but misses the clock. although this is clearly visible in the trace.
at 200khz the decoding works fine, but the end of the last byte is missed, (the CS line goes high, but the data bubble continues on)
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby Martyn » Wed Jun 20, 2012 9:15 am

Can you post a psdata file showing the issue for us to take a look at. Go to "File->SaveCurrentWaveform" and save as .psdata

Thanks
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby bunjatec » Wed Jun 20, 2012 11:16 am

Attached waveform as requested.

in the attached file the 4 signals are:
D0, CS
D1, SDI
D2, SD0
D3, SCLk
from the waveforms at 5.44us
should decode as:
SDO, AB,00,00,00
SDI, 00,00,00,29
Attachments
20120620-0003.psdata
file showing SPI issue
(11.08 KiB) Downloaded 181 times
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby Martyn » Thu Jun 21, 2012 7:52 am

Can you try with a Collection Time of 200us/div so that you increase the sampling rate, and then repost the psdata file.
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby bunjatec » Thu Jun 21, 2012 11:46 am

200us/div as requested,
10MS/sec
can see waveforms clearly (and can read the data on them), but data decoding not even close.
Attachments
20120620-0004.psdata
(11.81 KiB) Downloaded 184 times
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby Martyn » Fri Jun 22, 2012 9:39 am

I have passed the information and traces on to the development team for investigation.

While I am waiting for a definitive answer from then, and looking at the trace, I would suggest that it is not correctly locking onto the clock so can you try a few different timebases to see if it helps decode any part of the signal correctly.
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby bunjatec » Fri Jun 22, 2012 4:17 pm

Hi,
I tried a number of different timebases.. this was one of the first things I thought may have caused problems, but to no avail.. :(
I have some other work to get on with for the next day or so, but will hopefully get back to this afterwards.
I look forward to getting some response from the dev team..
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby Martyn » Thu Jul 19, 2012 8:51 am

We have tried this on the latest beta release and by removing the serial decode settings and then adding them back but setting a falling edge clock, MSB first, we are able to decode 01, 03, 05 as a repeating sequence.

Is this what you would expect for the 20120620-0004.psdata file on D2, SD0
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby bunjatec » Tue Aug 07, 2012 8:13 am

This seems about right..
What was wrong?
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Re: 2205MSO SPI decoding not working at high speed (2Mhz)

Postby Martyn » Tue Aug 07, 2012 9:28 am

The issue is making sure that the starting point and conditions for decode are correct.
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