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dotcypress / ula

μLA: Micro Logic Analyzer for RP2040
Apache License 2.0
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RP2040 sampling incorrect #8

Open Volhout opened 9 months ago

Volhout commented 9 months ago

I used version ula_0.0.2 and also version ula_0.0.3 on 2 different genuine RP pico's (no clones). With PulseView (nightly build, the last "stable" build 0.4.2 does not connect to the RP2040).

When pico is connected to a stable square wave generator signal of 100kHz, 3.3V high, 0V low, (GP15) withg good ground connection between generator and RP2040 I see 2 artefacts

1/ Sometimes data from channel 15 shows up on the channel 7 waveform in pulseview. This can very well be pulseview causing it.

2/ When I use sampling rate 1MHz, I see a nice square wave. When I use 10MHz the waveform is irregular (some pulses are not the correct pulse width). When I sample at 100Mhz the 100kHz square wave is not recognisable. In each pulse there are missing samples (low in stead of high).

Note, I am not using triggers, just RUN in pulseview.

kukrimate commented 9 months ago

I seem to be having the exact same issue.

It seems like a Linux-only sigrok bug to me however, as it only happens under Linux, not macOS, have tested both.

As an absolutely wild guess, this might be related to the Linux serial port code opening the USB tty device in cooked mode for some inexplicable reason, and some bytes being treated as ANSI escape sequences.