On Fri, Aug 19, 2022 at 10:44:06AM +0300, Farber, Eliav wrote: > On 8/18/2022 11:23 PM, Guenter Roeck wrote: > > On Wed, Aug 17, 2022 at 05:43:17AM +0000, Eliav Farber wrote: > > > Modify the equation and coefficients to convert the digital output to > > > temperature according to series 5 of the Moortec Embedded Temperature > > > Sensor (METS) datasheet: > > > T = G + H * (n / cal5 - 0.5) + J * F > > > > > > The G, H and J coefficients are multiplied by 1000 to get the > > > temperature > > > in milli-Celsius. > > > > > > > This is, at the very least, confusing. It doesn't explain the discrepancy > > to the old code nor the change in constant values. I have no idea if this > > change would result in erroneous readings on some other system where > > the existing calculation may be the correct one. > > When I tested the driver it was also not clear to me why the equation > and coefficients in the code don't match the specifications in the data > sheet. > I reached out to Maxlinear engineers (@rtanwar) and they also couldn't > explain the discrepancy. > After further correspondence I aligned both the equation and coefficients > in the driver code to the equation and coefficients defined in series 5 > of the Moortec Embedded Temperature Sensor (METS) datasheet which they > provided. > At least some of the discrepancy is because the original code is more optimized and avoids overflow. Either case, the above needs to be explained in the commit description. > > On top of that, it seems overflow-prune in 32 bit systems. > > I'll check if it can overflow, and if it can I'll fix in next version. > > -- > Regards, Eliav >
