SPI Clock issue


I use Beaglebone Black as SPI master. It is a reliable hardware.
But as you can see the SPI clock not picked properly by Saleae Logic Pro 8. It is not a square wave, they are random spikes.

  • I have tested on other channels but the results are same.
  • Even SPI analyser is not set, the channel can not pick the clock wave. There are just spikes.
  • If I apply 1us glitch filter to clock channel, the spikes disappears and no data shown on the channel.

BBB_spi_clock_issue.sal (63.4 KB)

Do you have any idea what causes this problem? Thanks

Those random spikes are called « glitches » and can be filtered out.

Please refer to What are glitches?.

@akif To add to @rei_vilo 's suggestion, I also noticed that the SPI clock doesn’t seem to be recorded properly by channel 0.

What voltage levels does your SPI signal swing between? Your voltage setting is currently set to 3.3V, which means the signal needs to cross 1.65V to properly register a digital transition in our software. You may want to try a lower voltage setting.

It may also be useful to enable analog channel 0 to double check the SPI clock activity.

In this case I don’t think they are glitches. I think, as Tim suggests, that they are improperly recorded clock signals, probably due to a logic level issue.

Usually glitches show up as extra edges, but in this case where the clock edges should show an almost solid band, there are only occasional spikes, so missing edges, not extra edges.