On Fri, Apr 07, 2023 at 06:19:47PM +0100, Jonathan Cameron wrote: > On Wed, 5 Apr 2023 23:22:32 +0200 > Patrik Dahlström <risca@xxxxxxxxxxxxxx> wrote: > > > The palmas gpadc block has support for monitoring up to 2 ADC channels > > and issue an interrupt if they reach past a set threshold. This change > > hooks into the IIO events system and exposes to userspace the ability to > > configure these threshold values for each channel, but only allow up to > > 2 such thresholds to be enabled at any given time. Trying to enable a > > third channel will result in an error. > > > > Userspace is expected to input calibrated, as opposed to raw, values as > > threshold. However, it is not enough to do the opposite of what is done > > when converting the other way around. To account for tolerances in the > > ADC, the calculated raw threshold should be adjusted based on the ADC > > specifications for the device. These specifications include the integral > > nonlinearity (INL), offset, and gain error. To adjust the high > > threshold, use the following equation: > > > > (calibrated value + INL) * Gain error + offset = maximum value [1] > > > > Likewise, use the following equation for the low threshold: > > > > (calibrated value - INL) * Gain error - offset = minimum value > > > > The gain error is a combination of gain error, as listed in the > > datasheet, and gain error drift due to temperature and supply. The exact > > values for these specifications vary between palmas devices. This patch > > sets the values found in TWL6035, TWL6037 datasheet. > > > > [1] TI Application Report, SLIA087A, Guide to Using the GPADC in > > TPS65903x, TPS65917-Q1, TPS65919-Q1, and TPS65916 Devices. > > > > Signed-off-by: Patrik Dahlström <risca@xxxxxxxxxxxxxx> > Hi Patrik, > > A few really trivial formatting things inline. If we don't end up > with a v4 for other reasons I can tidy this stuff up whilst applying. I'll send in a v4 later today :) > > Jonathan > >
