Hi guys,
First, thanks a ton for all the devs' work on Sigrok! It's really a great,
easy to use tool.
I'm using the CSV output and some Python to do signal analysis for firmware
testing, and ran into a bug where the reported CSV time was advancing too
fast, causing errors in my post-processing of the CSV file:
https://sigrok.org/bugzilla/show_bug.cgi?id=1027
The error is caused because there is a round-down error when 1/sampling
rate is not an integer number of nanoseconds. That slightly too small
"period" variable is accumulated on each sample, leading to a speed-up
in the reported time in the CSV.
I've got a simple patch which avoids the error by doing the math at the
point of use, and not accumulating error.
https://github.com/earlephilhower/libsigrok/commit/5f314d2f708ae0721e743814f
5236df46dee538a
I've tested in my own use case (show below sampling a 1khz waveform with
a 12mhz samplerate), and it's easy to reproduce with any other non-integer
period sampling rate.
Thanks,
-Earle F. Philhower, III
earlephilho...@yahoo.com <mailto:earlephilho...@yahoo.com>
---without patch---
earle@server:~/src/libsigrok$ sigrok-cli -d fx2lafw -C D1 -c
samplerate=12mhz -O csv:dedup=true --samples 100000
; CSV generated by libsigrok 0.5.0
; from fx2lafw (generic driver for FX2 based LAs) on Sat May 2 10:56:54
2020
; Channels (1/8): D1
; Samplerate: 12 MHz
nanoseconds,logic
83,0
252403,1
750486,0
1248486,1
1746569,0
2244569,1
2742652,0
3240652,1
3738735,0
4236818,1
4734901,0
5232901,1
5730984,0
6228984,1
6727067,0
7225067,1
7723150,0
8221150,1
8300000,1
---with-patch---
earle@server:~/src/libsigrok$ sigrok-cli -d fx2lafw -C D1 -c
samplerate=12mhz -O csv:dedup=true --samples 100000
; CSV generated by libsigrok 0.5.0
; from fx2lafw (generic driver for FX2 based LAs) on Sat May 2 10:40:51
2020
; Channels (1/8): D1
; Samplerate: 12 MHz
nanoseconds,logic
0,0
273583,1
773583,0
1273666,1
1773750,0
2273750,1
2773833,0
3273833,1
3773916,0
4274000,1
4774083,0
5274166,1
5774250,0
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