checksum phase in the I2C model shown bellow for si7021


Joined Feb 24, 2006
RTFDS p.19 § 5.1
Optionally, a checksum byte can be returned from the slave for use in checking for transmission errors. The checksum byte will follow the least significant measurement byte if it is acknowledged by the master. The checksum byte is not returned if the master “not acknowledges” the least significant measurement byte. The checksum byte is calculated using a CRC generator polynomial of x8 + x5 + x4 + 1, with an initialization of 0x00. The checksum byte is optional after initiating an RH or temperature measurement with commands 0xE5, 0xF5, 0xE3, and 0xF3. The checksum byte is required for reading the electronic ID with commands 0xFA 0x0F and 0xFC 0xC9. For all other commands, the checksum byte is not supported