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| author | Beomho Seo <beomho.seo@samsung.com> | 2014-02-10 09:52:28 +0900 |
|---|---|---|
| committer | Chanho Park <chanho61.park@samsung.com> | 2014-03-20 17:43:39 +0900 |
| commit | 19afba11df5dff50601104f9a92bf806e3c939d1 (patch) | |
| tree | 3c0d82e357d1833e3f777824e7783334c9c1ba0a | |
| parent | e14784394429cc88f58bff633f414b2fa2cd982b (diff) | |
| download | linux-3.10-19afba11df5dff50601104f9a92bf806e3c939d1.tar.gz linux-3.10-19afba11df5dff50601104f9a92bf806e3c939d1.tar.bz2 linux-3.10-19afba11df5dff50601104f9a92bf806e3c939d1.zip | |
iio: ak8975: Fix calculation formula for convert micro tesla to gauss unit
Oen micro tesla equal 0.01 gauss. So I have fixed calculation formula And add RAW_TO_GAUSS macro.
ASA is in the range of 0 to 255. If multiply 0.003, calculation result(in_magn_[*]_scale) is
always 0. So multiply 3000 and return IIO_VAL_INT_PLUS_MICRO.
As a result read_raw call back function return accurate scale value.
Change-Id: Ia00b801d4867955eef661b64add82ca634f0256c
Signed-off-by: Beomho Seo <beomho.seo@samsung.com>
| -rw-r--r-- | drivers/iio/magnetometer/ak8975.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c index 7105f22d6cd..9edf4c935fd 100644 --- a/drivers/iio/magnetometer/ak8975.c +++ b/drivers/iio/magnetometer/ak8975.c @@ -85,6 +85,7 @@ #define AK8975_MAX_CONVERSION_TIMEOUT 500 #define AK8975_CONVERSION_DONE_POLL_TIME 10 #define AK8975_DATA_READY_TIMEOUT ((100*HZ)/1000) +#define RAW_TO_GAUSS(asa) ((((asa) + 128) * 3000) / 256) /* * Per-instance context data for the device. @@ -265,15 +266,15 @@ static int ak8975_setup(struct i2c_client *client) * * Since 1uT = 100 gauss, our final scale factor becomes: * - * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100 - * Hadj = H * ((ASA + 128) * 30 / 256 + * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100 + * Hadj = H * ((ASA + 128) * 0.003) / 256 * * Since ASA doesn't change, we cache the resultant scale factor into the * device context in ak8975_setup(). */ - data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8; - data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8; - data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8; + data->raw_to_gauss[0] = RAW_TO_GAUSS(data->asa[0]); + data->raw_to_gauss[1] = RAW_TO_GAUSS(data->asa[1]); + data->raw_to_gauss[2] = RAW_TO_GAUSS(data->asa[2]); return 0; } @@ -428,8 +429,9 @@ static int ak8975_read_raw(struct iio_dev *indio_dev, case IIO_CHAN_INFO_RAW: return ak8975_read_axis(indio_dev, chan->address, val); case IIO_CHAN_INFO_SCALE: - *val = data->raw_to_gauss[chan->address]; - return IIO_VAL_INT; + *val = 0; + *val2 = data->raw_to_gauss[chan->address]; + return IIO_VAL_INT_PLUS_MICRO; } return -EINVAL; } |