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Fanspeed and temperature Reporting 635+SCAB


New member

i'm using a modified test635 C source to program temperature and fanspeed reporting. I run this command in a loop every 500ms to read out the values:
int timed_out = 1;		
     for(int k=0;k<=10000;k++)
The program is running under linux and if I set fan 1 to 84% and enable fanspeed report I recieve this from the function ShowReceivedPacket()

C=129( 1 = Read Version),L=4,D="\000\011\172N",CRC=0xB7FF5F95

The values after D="\000\ vary and I can not find any logic. The first three 000 tell me which fan is reported but the rest looks very confusing to me.

The same when I use temperature reporting, I use the same function as above and I'll get this:

C=130( 2 = Write Flash),L=4,D="\000v\001\001",CRC=0xB7FB893B

Can someone tell me what I have to change in that function, so that I get "real" values?!


I think it is because the incoming data is being formated to a string. If I look at it with a packet sniffer the structure of the packets look like it is described in the manual.
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Last edited:

CF Mark

The data back from the CFA-631/CFA-633/CFA-635 will not be plain real values.
You have to put them through a formula to get the correct results.

See "0x81: Fan Speed Report (SCAB required)" in the CFA-635 datasheet, or even better, the 635_WinTest sourecode for information.


New member
Oh, that's true! There is some more information at the beginning of the manual I didn't recognize...

Thanks for pointing me the right way!