omron_protocol_notes.asciidoc update (Omron 790IT Protocol Documentation) #25
Description
During reverse engineering of latest version of Omron software I discovered some not-documented-yet details of Get Individual Reading (GME) return value format.
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Byte 6 (claimed UNKNOWN now) is 'Unit Number'. Value of such byte is not used by software.
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Byte 7 (claimed UNKNOWN now) is part of SYS value which is big-endian two byte value, not just single byte 8. Remember - 790IT can measure SYS up to 300mmHg
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Byte B (claimed UNKNOWN now) is part of big-endian two byte value together with byte C. The resulting word is bitfield, where
--- &0x0001 (FPULFLAG) is one bit flag 'Irregular heartbeat detected during measurement'
--- &0x0002 (MOVEFLAG) is one bit flag 'Movement detected during measurement'
--- &0x0030 (CNT) is two bit number related to TrueRead function (it's correctly documented in current version of document).
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Note that this format of GME response apply not only to HEM-790IT (M7080IT, M7080) but also to BP791IT (M7222IT), Elite 7300IT (M7300IT), HEM-670IT (M6040IT, M637IT) and 1500PRO (M1040).
Model HEM-637 (M637IT) lacks flags (word B+C), the PUL (byte A) is immediately followed by checksum instead.