On 05/27/11 11:23, Michael Hennerich wrote: > On 05/27/2011 11:44 AM, Jonathan Cameron wrote: >> ... >>> Hi Jonathan, >>> >>> >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> ls >>> device0:buffer0 power >>> in-in_scale range >>> in0-in0_raw range_available >>> in1-in1_raw sampling_frequency >>> in2-in2_raw sampling_frequency_available >>> in3_raw subsystem >>> in4_supply_raw temp0_raw >>> in4_supply_scale temp_scale >>> in_scale trigger >>> name uevent >>> >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in_scale >>> 0.000140 >>> >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat range_available >>> 2500 1250 625 312 156 78 39 19 >>> >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 312> range >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in_scale >>> 0.000010 >>> >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 78> range >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in_scale >>> 0.000000 >>> root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> >>> >>> with these 24-bit converters and input AMPs we are already exhausted >>> the number of available digits we have for scale. >> Time for a new return type and extra logic in the core. >> IIO_VAL_INT_PLUS_NANO >> >> should still fit in a 32 bit long. Perhaps it's better to make a bigger jump - or >> this will just bite us again sometime soon. >> >> After nano we will have to start having padding zeros which is going to be a little >> strange - or I guess we don't have to keep val as being int... >> >> IIO_VAL_MICRO_PLUS_PICO maybe? The maximum option of IIO_VAL_NANO_PLUS_ATTO seems a little >> 'odd'. >> >> The more complex question is going to be writing values that are this small. I think we will >> have to add another callback into the drivers where they can query what format a value should >> be in so the core can provide it. Make this optional so it doesn't effect the majority >> of drivers where int + micro does the job. >> > IIO_VAL_INT_PLUS_NANO should do the job for now. > >>> What shall we do? >>> >>> Also how would you name AIN1(-) - AIN1(-)? >>> >>> #define AD7793_CH_AIN1P_AIN1M 0 /* AIN1(+) - AIN1(-) */ >>> #define AD7793_CH_AIN2P_AIN2M 1 /* AIN2(+) - AIN2(-) */ >>> #define AD7793_CH_AIN3P_AIN3M 2 /* AIN3(+) - AIN3(-) */ >>> #define AD7793_CH_AIN1M_AIN1M 3 /* AIN1(-) - AIN1(-) */ >>> >>> in0-in0_zerooffset_raw ? >> Hmm.. That is awkward. Given only the channel numbers exist in event codes >> it will also possibly cause us issues at some later date. >> How about having in0-in0_raw then in0-in0_offset + in0-in0_offset_available. >> (actually this would be shared I guess so in-in_offset_available). >> A little clunky, but does fit better within the api. Is there a real use case >> for buffering where one grabs both offsets in the same scan? > As far as I understand things - We do zero and full scale calibration, > The results read from the other channels should have the offset eliminated. > I agree the offset read from AIN1(-) - AIN1(-) should be the same for all channels. > So in-in_offset sounds good to me - why _available? Because there are two options possible. One when we are doing signed output and one for differential but with only positive values possible. >> Jonathan >> >> -- >> 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 >> > > -- 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
