On 07/28/11 13:47, Manuel Stahl wrote: > Am 28.07.2011 11:52, schrieb Jonathan Cameron: >> On 07/28/11 09:33, Manuel Stahl wrote: >>> Hi, >>> >>> I had the time to read through the discussion recently, so just a few comments: >>> >>> Am 28.07.2011 10:08, schrieb Hennerich, Michael: >>>> Jonathan Cameron wrote on 2011-07-28: >>>>> On 07/27/11 15:41, Michael Hennerich wrote: >>>>>> On 07/26/2011 01:06 PM, Jonathan Cameron wrote: >>>>>>> On 07/26/11 11:52, Michael Hennerich wrote: >>>>>>>> On 07/26/2011 11:17 AM, Jonathan Cameron wrote: >>>>>>>>> On 07/26/11 10:01, Hennerich, Michael wrote: >>>>>>>>>> Jonathan Cameron wrote on 2011-07-25: >>>>>>>>>>> Michael pointed out the issues that not having an explicit >>>>>>>>>>> direction for channels was causing and the inconsistency of the >>>>>>>>>>> inX and outX channel naming we got from hmwon. >>>>>>>>>>> >>>>>>>>>>> They are stuck with it, but we aren't, so lets fix this now. >>>>>>>>>>> >>>>>>>>>>> Interesting question is whether we reset the base units to be >>>>>>>>>>> volts whilst we are at it? (for voltage channels obviously!) >>>>>>>>>> What do you mean exactly volts versus milli volts? >>>>>>>>> Make the in_voltage_scale correspond to conversion to volts instead >>>>>>>>> of millivolts as now (I think). Err. Looking at it that isn't >>>>>>>>> actually documented... oops. I wonder which drivers actually do >>>>>>>>> that and which don't. >>>>>>>> The ones I wrote provide the scale for millivolts. >>>>>>>> With the recent introduction of IIO_VAL_INT_PLUS_NANO we got the >>>>>>>> scale accurate enough for the precession 24-bit converters. >>>>>>>> If we move to the SI base unit volt, we lose this accuracy again. >>>>>>> Yup, that's the principal counter argument to the change. >>>>>> If we decide to leave the milli scale for volts... Do we also want to >>>>>> stay with milli degrees Celsius, etc.? If we do it for one, probably >>>>>> best to do it for them all.. >>>> Hi Jonathan, >>>> >>>> So stick with the milli scale for all? >>> If it's possible, I would like to have pure units. I didn't read the >>> API with IIO_VAL_INT_PLUS_NANO completely so I don't understand the >>> problem yet, but using milli just because the drivers we have in >>> place can measure relatively low voltages make no sense for me. >> The issue is we have two integers to play with. The first is >> used for the integer part. The second is divided by either 10^6 or 10^9 >> and added on. >> >> If we go to 10^12, then max value for the decimal bit should be: >> 999,999,999,999. >> >> Unfortunately we only have a 32 bit int (to avoid use of div64 in drivers). >> It's signed as well to allow us to set the integer bit to 0. Hence max >> value is 2^31 = 2 147 483 648. >> >> Hence not enough and the hole. >> >> Next question is whether this is an issue. I doubt it with _scale, _offset >> _calibbias, but just possibly with _calibscale where very small adjustments >> may occur (hence 0.999999999999 is possible.) > Does it help to support exponential formats like 999999.9999999e-10? Nasty... I'd rather just put more bits the two values if we need to. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
