ADLINK CoreExpress-ECO2 - Manual (Page 31)

4.25 Get Fan Speed
This command reads the current Speed of the CPU Cooler Fan. It delivers the Fan Speed in RPM.
START SMC_addr ACK command ACK START (Repeat) SMC_addr+1 ACK
length ACK(C) MSB_byte ACK(C) LSB_byte ACK(C) STOP
Table 4.25.1 SMC transmitter format of the Get Fan Speed Command Code
ITEM DESCRIPTION
START SM-bus start condition
SMC_addr 0x50 (8-bit)
ACK SM-bus acknowledge condition generated by receiver
command 0x68 = “Get Fan Speed” Command code
length 0x02 = 2 Bytes data length
MSB byte
LSB byte
16-Bit data value of Fan Speed (RPM)
STOP SM-bus stop condition
Table 4.25.2 Explanation of Table 4.25.1