Hi Matti, On Mon, Oct 24, 2022 at 6:10 PM Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote: > > KX022A is a 3-axis accelerometer from ROHM/Kionix. The sensor features > include variable ODRs, I2C and SPI control, FIFO/LIFO with watermark IRQ, > tap/motion detection, wake-up & back-to-sleep events, four acceleration > ranges (2, 4, 8 and 16g), and probably some other cool features. This is a nice driver, and I found it very helpful as a reference. One question regarding scale please see below. > + * range is typically +-2G/4G/8G/16G, distributed over the amount of bits. > + * The scale table can be calculated using > + * (range / 2^bits) * g = (range / 2^bits) * 9.80665 m/s^2 > + * => KX022A uses 16 bit (HiRes mode - assume the low 8 bits are zeroed > + * in low-power mode(?) ) > + * => +/-2G => 4 / 2^16 * 9,80665 * 10^6 (to scale to micro) > + * => +/-2G - 598.550415 > + * +/-4G - 1197.10083 > + * +/-8G - 2394.20166 > + * +/-16G - 4788.40332 > + */ > +static const int kx022a_scale_table[][2] = { > + { 598, 550415 }, > + { 1197, 100830 }, > + { 2394, 201660 }, > + { 4788, 403320 }, > +}; Given that the integer part is non-zero, and IIO_VAL_INT_PLUS_MICRO is returned for read_scale, As raw value will never be fractional how does this correspond to a reading of 9.8 m/s² for the Z-axis? > + > +static int kx022a_read_avail(struct iio_dev *indio_dev, > + struct iio_chan_spec const *chan, > + const int **vals, int *type, int *length, > + long mask) > +{ > + switch (mask) { > + case IIO_CHAN_INFO_SAMP_FREQ: > + *vals = (const int *)kx022a_accel_samp_freq_table; > + *length = ARRAY_SIZE(kx022a_accel_samp_freq_table) * > + ARRAY_SIZE(kx022a_accel_samp_freq_table[0]); > + *type = IIO_VAL_INT_PLUS_MICRO; > + return IIO_AVAIL_LIST; > + case IIO_CHAN_INFO_SCALE: > + *vals = (const int *)kx022a_scale_table; > + *length = ARRAY_SIZE(kx022a_scale_table) * > + ARRAY_SIZE(kx022a_scale_table[0]); > + *type = IIO_VAL_INT_PLUS_MICRO; > + return IIO_AVAIL_LIST; > + default: > + return -EINVAL; > + } > +} Regards Jagath