Reverse Engineering - B550M ITX/AC

[dredvard]

B550M-ITX/AC board received this reply with a Read Header Command. This board only has 4 LEDs. This might be the number of programable LED. There was 100 ARGB attached to it. With Bios 1.50. Max LED Count Command Read Header 02 : 14 00 02 Reply: A6 00 00 02 01 01 64 50 1e 1e 1e 1e

LED in order are: RGB1 RGB2 ARGB1 ARGB2 IO PCH PCB AUDIO B550 Steel 01 01 50 50 05 07 1E 1E B550M-ITX/AC 01 01 64 50 1E 1E 1E 1E The B550 was tested with ARGB that has 100 . And I think IO has 5 and PCH has 07 respectively. 1E is for unusable is interesting because that corresponds to 30. Not sure what happens if max addressable led is set to 30 (1E).

RGB Swap Command Read Header 03: 14 00 03 Reply : A6 00 00 00 03 1C

The reply format is 1C on B550M vs 4. B550M (with 4 zones) 1C = 01 1100 vs Steel Legend (with 6 zones) 4C = 0100 1100 . This is probably a bit wise evaluation in the following order with a terminating 1 based on max zones from Read 02 command.
Audio PCB PCH IO ARGB2 ARG1 RGB2 RGB1 With 1 being RGB Swap ON

Unknow Header Read Command Read Header 01 : 14 00 01 Reply: A6 00 00 01 05 The reply is 05 for B550M-ITX/AC vs 3F for B550 Steel Legend In bits 05 = 0101 vs 3F = 11 1111 But this doesn’t seem to correspond to anything. Maybe firmware version or model?