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| SPI Triggering Issue on SDS1104x-e Scope |
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| mrprecision:
Hi, I use a Siglent SDS 1104X-E Scope with the firmware 8.1.6.1.26. I use the SPI decode which works fine. I send two bytes of date in a message to an dac with the usage of chip select. I setup the trigger to SPI to catch the dataword 0xFFFF as you can see in the image. No if I increase the "break" between the two bytes (time between cursors) from 350ns only a little bit, than the trigger is not catching the 0xFFFF dataword anymore. I don't change anything on the scope. I only delay the secound byte by firmware. Is there any timeout? I don't use CLK Timeout in the scope. I use ~CS. Why is the SPI trigger not working it the secound byte is delayed mor than 350ns? Can anyone help me? |
| tautech:
Your waveforms don't look right.....like ch1 is a clock not the data stream. Here's a screenshot of SPI from Siglents STB3......no Decode trigger, just a falling edge trigger with enough holdoff to not trigger again within the same packet. |
| mrprecision:
Hi, I don't agree. On my scope image CH1 ist the SPI Clock, CH2 the SPI Data 0xFF, CH3 the ~CS. I use the SPI Trigger Function with (CLK, MOSI, ~CS, no CLK timeout) for the Dataword 0xFF. As you can see, after the secound byte the Scope triggers. Everything fine. Now I increase the delay a little bit betwenn the two bytes. The scope not tiggering any more. Is there any timeout? |
| tautech:
--- Quote from: mrprecision on December 03, 2018, 06:26:02 am ---Hi, I don't agree. --- End quote --- OK, let's work through this with what we know. Your screenshot: --- Quote ---On my scope image CH1 ist the SPI Clock, CH2 the SPI Data 0xFF, CH3 the ~CS. --- End quote --- OK, my image: Ch 1 = clock Ch 2 = MOSI We see a clock for each data transmission and while I am no SPI expert I do wonder about the SPI implementation you have used. :-// Is it wrong, I'm sorry I do not know....maybe an SPI guru can help. --- Quote ---I use the SPI Trigger Function with (CLK, MOSI, ~CS, no CLK timeout) for the Dataword 0xFF. As you can see, after the secound byte the Scope triggers. Everything fine. Now I increase the delay a little bit betwenn the two bytes. The scope not triggering any more. --- End quote --- If we look at your screenshot again, the trigger appears to be on the rising edge of Ch 1 when to get correct Decode timing it should be on the falling edge. Maybe go through and double check channel assignments and other decode settings. --- Quote ---Is there any timeout? --- End quote --- Timeout as in like trigger holdoff, no not in the Decode trigger suite. |
| mrprecision:
--- Quote ---If we look at your screenshot again, the trigger appears to be on the rising edge of Ch 1 when to get correct Decode timing it should be on the falling edge. Maybe go through and double check channel assignments and other decode settings. --- End quote --- My SPI Slave is running on the raising edge of the CLK, therefore the trigger appears corret. For me everything is fine. But why is it not working for longer delays between the two bytes. --- Quote ---Timeout as in like trigger holdoff, no not in the Decode trigger suite. --- End quote --- For the trigger I use the SPI decoder. The only settings are ~CS, MOSI, CLK. There is no trigger holdoff or any timeout. Why is the delay between the two bytes important? |
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