Bug 1484 - The DMX512 decoder "skips" slots this getting out of step
Summary: The DMX512 decoder "skips" slots this getting out of step
Status: RESOLVED DUPLICATE of bug 1442
Alias: None
Product: libsigrokdecode
Classification: Unclassified
Component: PD: dmx512 (show other bugs)
Version: 0.5.2
Hardware: x86 Windows
: Normal major
Target Milestone: ---
Assignee: Nobody
Depends on:
Reported: 2020-01-05 16:04 CET by Graham
Modified: 2020-01-10 18:37 CET (History)
1 user (show)

Start of DMX packet shoing skipping slots 1 and 4 (21.05 KB, image/png)
2020-01-05 16:04 CET, Graham

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Description Graham 2020-01-05 16:04:18 CET
Created attachment 579 [details]
Start of DMX packet shoing skipping slots 1 and 4

In my test DMX stream, all slots upto and including slot 14 are zero.
My configuration currently only has devices on channels 15 - 23 (4xRGB)

The attached screenshot shows that the decoder correctly recognises the initial BREAK, MAB and Start Code.

However, it then completely misses the START bit for Slot 1 and labels it as "InterFrame" (surely, any gap between Slots should be a continuous MARK not SPACE).

The decoder then incorrectly identifes the Stop Bits from the real Slot 1 as a bad START bit (BY Definition a SPACE but this is MARK!) with the second STOP bit becoming the LSB 1 reported for "Channel 1".

Since the decoder started this slot too early, it then reports the last two (MS) bits as BAD STOP bits.  The actual SRTOP bits are reported as "InterFrame" again

The START bit for the next slot is correctly detected and the whole slot is correctly decoded - but reported as Channel 2 when it should be Channel 3.

The sequence then repeats, with the decoder missing the START bit for the next slot, incorrectly decoding the next slot as it did before and correctly decoding the next slot.
Comment 1 Gerhard Sittig 2020-01-05 16:11:26 CET
Duplicate of bug 1442?
Comment 2 Gerhard Sittig 2020-01-10 18:37:30 CET
Closing as a duplicate of bug 1442, see also bug 1483.

*** This bug has been marked as a duplicate of bug 1442 ***