Decoding OBDII Comms

[retepsnikrep]

Thanks for the ideas so far.

Here is some more refined data for a few functions.

'MPI_MDL Temp C
'$9C = 21C
'$88 = 29C
'$83 = 31C
'$6B = 40C
'$67 = 42C

'DC-DC Converter Temp C
'$97 = 22C
'$7F = 33C
'$77 = 36C
'$76 = 37C
'$72 = 39C

Any ideas on these two?

[retepsnikrep]

Some new data to fox you from an Air Fuel ratio sensor.

The data from the car (left number) converts to the AF (Right number).

255=7.31
224=8.36
192=9.71
160=11.65
128=14.56
96=19.41
64=29.12
32=58.24
16=116.48
8=232.96
4=465.92
2=931.85
1=1863.70

It looks like a typical wideband 02 sensor response with a very steep rise at the end.

I need to establish a formula (if possible) from this data so I can convert the data into the AF.

Now I could capture every value from 0-255 and get exact numbers for each value but that will take a lot of time, and then I would have to do a lookup table for the normal operating range. I could just gather 128 data points from 64 to 192, that encompases the AF range 29.12 - 9.71 which i'm sure covers my cars operating area.

How can I do it without using a look up table? Formula?