Trace is varied even no code between trigger_high and trigger_low

[helloyorld]

I wrote a code as following
trigger_high();
trigger_low();
pt[0] = 0xFF;
simpleserial_put(‘r’, 8, pt);

then I capture the trace with 22400 samples setting. The trace I got is as below:

Interesting, once the trigger_high() starts, it captures everything but trigger_low() does not stop the capturing immediately. It seems like the trigger_low() stop the scope to be trigger continuously. Also, the time of scope to restart capturing is fixed.

My questions are:

1. What is the time that the chipwhisperer will restart the capture ? I’m using Chipwhisperer Lite.
2. Once I start the trigger_high(), it starts to record the trace from the first signal to the signal 22400 and these are the samples I get when I call get_last_trace(), correct?

[Alex_Dewar]

@helloyorld

trigger_low() does not stop the capturing immediately

Correct. How many samples are captured depends purely on scope.adc.samples and not any feedback from the target.

@helloyorld

What is the time that the chipwhisperer will restart the capture ? I’m using Chipwhisperer Lite.

Next capture will take place after you call scope.arm() and another rising edge trigger event occurs.

@helloyorld

Once I start the trigger_high() , it starts to record the trace from the first signal to the signal 22400 and these are the samples I get when I call get_last_trace() , correct?

Yup, that’s correct.

[helloyorld]

@Alex_Dewar

Correct. How many samples are captured depends purely on scope.adc.samples and not any feedback from the target.

So what is the functionality of trigger_low() exactly ? Is it used to stop the scope to trigger itself continuously ?

@Alex_Dewar

Next capture will take place after you call scope.arm() and another rising edge trigger event occurs.

Continue to the previous question, aftertrigger_low()is called, the trigger_high() after the trigger_low() will not be activated unless scope.arm() activates the scope. Am I right?

[Alex_Dewar]

@helloyorld

So what is the functionality of trigger_low() exactly ? Is it used to stop the scope to trigger itself continuously ?

By default, the scope triggers on a rising edge of the trigger pin. It needs to be set low after an encryption so it can be set high again for the next encryption.

@helloyorld

Continue to the previous question, after trigger_low() is called, the trigger_high() after the trigger_low() will not be activated unless scope.arm() activates the scope. Am I right?

Correct