On Thu, Aug 13, 2009 at 10:43:08AM -0700, Ira W. Snyder wrote: > Hello all. > > I'm working on a driver (posted here previously) for the INA209 chip. > The chip itself has support for power and current readings, though they > will only be valid if a special calibration register is set > appropriately. The units used for interpreting the power and current > registers change depending on the value in the calibration register; > they are not constant. > > It is possible to calculate the power and current from userspace using > the sense resistor reading + the sense resistor value (which changes > between implementations). > > I am aware of the "calculate" lines in sensors3.conf, which should be > able to do this kind of calculation. > > My previous postings of this driver have mostly been ignored, probably > due to set the calibration register before use. This is something not > supported by the hwmon sysfs-interface. Using the userspace sensors > program to handle this instead removes the need to set the calibration > register. > > I have two possible solutions: > 1) Have curr1_input output the sense resistor voltage in mV and use the > sensors program (using "calculate") to convert it appropriately > 2) Have curr1_input always read back 0 uA, and have the sensors program > use in0_input (the sense resistor voltage in mV) in the calculate > line, ignoring the reading from curr1_input > > I can figure out how to use calculate for #1, but I cannot figure out > how to reference a different sensor in a calculate line. The > documentation claims this is possible, but I cannot find any examples. > Ignore the "I don't know how to use other sensor values from a compute statement" part of this. I've figured it out. compute power1 curr1_input * in1_input, curr1_input * in1_input Works perfectly for me. The power1_input value is calculated using the readings from curr1_input and in1_input. The rest of my questions still stand. Thanks, Ira
