fix: parse SZL 0x0011 records properly for S7-1500 - #789
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Real S7-1500 PLCs include a partial-list header (LengthDR + NDR) and per-record index fields in SZL 0x0011 responses. The previous code used hardcoded offsets that only worked when the MLFB started at byte 0. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Based on hardware testing by @fls-witturcom on S7-1516F: - Don't break on first record — S7-1500 puts version in record 0x0081 - Use negative indexing (rec[-3:]) for version bytes to handle both 26-byte (S7-300) and 28-byte (S7-1500) record layouts - Record 0x0081/0x0007 (active firmware) takes priority over 0x0001
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Summary
get_order_code()returning empty/corrupted data on S7-1500 CPUs (regression in pure Python 3.x)parse_order_code_szlnow properly parses the SZL partial-list header (LengthDR + NDR) and iterates through records to find the first non-empty MLFBCloses #783
Test plan
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