Logic analyzer - SPI

[Marc1992]

Hi,

I'm trying to correctly read data from a spi line. Whenever I'm capturing data, glitches from the SS line make the software wrongly interpret the bytes. As you can see on the picture that I attached, the byte should be interpreted as 108. Here, the software cuts the byte in two and interprets it as ?96 and ?0.

What should I do?

I have another question. I'm trying to record two spi words of 8 bits, but that are separate by few milliseconds. How can I capture both bytes? Repeated mode makes the data acquisition great, but I am only able to capture the last word of the two (since the software clears the data whenever a new word comes in). When I am using Record mode, I always get the error: "Sample might got lost!. Reduce sample rate" which I do, but the software only successfully captures both words 1 out of 5 times. Shift and Screen mode only allows 2kHz sample rate, which is not enough.

Is it possible to use the Protocol interface in the software to probe data from a spi line, like for the UART protocol interface where you click on Receive and you can see data coming in (without the need to execute a command like in the spi Protocol interface).

[attila]

Hello,

It looks like you have some crosstalk on the wires. The SS signal catches some spikes (from the clock and data signals) and this is interpreted as select deactivate/activate.
Try to isolate, have more distance between the wires or have each signal wire twisted with a ground wire.

Such 2MHz signal needs at least 4MHz sample rate. The 1-2MHz of record mode is not suffice.
Use repeated acquisition, set the update rate to 1ms and press run. This should capture trigger events even at 1-4ms distance.