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i use microcontroller and received ir frame of air conditioner SHARP. This Ir frame have 13 byte data (in decimal number, not hex) like below:

85 90 243 8 131 140 66 0 176 1 32 7 133 
85 90 243 8 142 140 66 0 176 1 32 7 136 
85 90 243 8 67 140 66 0 176 1 32 7 137 
85 90 243 8 78 140 66 0 176 1 32 7 132 
85 90 243 8 195 140 66 0 176 1 32 7 129

for hex value:

0x55 0x5A 0xF3 0x08 0x8E 0x8C 0x42  0x00 0xB0 0x20 0x07 0x88

0x55 0x5A 0xF3 0x08 0x43 0x8C 0x42 0x00 0xB0 0x20 0x07 0x89 

0x55 0x5A 0xF3 0x08 0x4E 0x8C 0x42 0x00 0xB0 0x20 0x07 0x84

0x55 0x5A 0xF3 0x08 0xC3 0x8C 0x42 0x00 0xB0 0x20 0x07 0x81

i was check XOR and SUM of 12 byte but can not calculate the checksum byte. How is that checksum is calculated ???

Byte 1 to 4 alway same value.

Byte 5: contain data for temperature.

Byte 6: contain ON/OFF mode

Byte 7 change the fan speed. Fan speed = 1, byte 7 = 0x42 Fan speed = 2, byte 7 = 0x4C Fan speed = 3, byte 7 = 0x4A Fan speed = 4, byte 7 = 0x4E Fan speed have wave symbol, byte 7 = 0x44 Fan speed auto, byte 7 = 0x45

Byte 8 alway 0x00 Byte 9 for swing value. Byte 10 alway 0x01 Byte 11 unclear byte 12 alway 0x07 byte 13 must be CRC value, but can not calcuate now.

Please help me.

  • Given that the upper 4-bits are always 0b100 in the last byte you list, I would imagine the checksum/fcs is only the last 4 bits – cimarron Jan 28 '18 at 4:50
  • @cimarron: i was check XOR of last 4 bit from byte 4 to byte 12. But still calculate CRC byte. – Hoang Duong Feb 1 '18 at 3:13

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