On Wed, 3 Jun 2015, Daniel Baluta wrote:
> This patch adds compensation formula to raw readings, borrowed
> from Memsic's input driver.
>
> Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> ---
> drivers/iio/magnetometer/mmc35240.c | 62 ++++++++++++++++++++++++++++++++++---
> 1 file changed, 58 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c
> index 88be660..902ad59 100644
> --- a/drivers/iio/magnetometer/mmc35240.c
> +++ b/drivers/iio/magnetometer/mmc35240.c
> @@ -58,6 +58,31 @@
> #define MMC35240_WAIT_CHARGE_PUMP 50000 /* us */
> #define MMC53240_WAIT_SET_RESET 1000 /* us */
>
> +/*
> + * Memsic OTP process code piece is put here for reference:
> + *
> + * #define OTP_CONVERT(REG) ((float)((REG) >=32 ? (32 - (REG)) : (REG)) * 0.006
> + * 1) For X axis, the COEFFICIENT is always 1.
> + * 2) For Y axis, the COEFFICIENT is as below:
> + * f_OTP_matrix[4] = OTP_CONVERT(((reg_data[1] & 0x03) << 4) |
> + * (reg_data[2] >> 4)) + 1.0;
> + * 3) For Z axis, the COEFFICIENT is as below:
> + * f_OTP_matrix[8] = (OTP_CONVERT(reg_data[3] & 0x3f) + 1) * 1.35;
> + * We implemented the OTP logic into driver.
> + */
> +
> +/* scale = 1000 here for Y otp */
> +#define OTP_CONVERT_Y(REG) (((REG) >= 32 ? (32 - (REG)) : (REG)) * 6)
MMC35240_ prefix
> +
> +/* 0.6 * 1.35 = 0.81, scale 10000 for Z otp */
> +#define OTP_CONVERT_Z(REG) (((REG) >= 32 ? (32 - (REG)) : (REG)) * 81)
> +
> +#define X_COEFFICIENT(x) (x)
> +#define Y_COEFFICIENT(y) (y + 1000)
> +#define Z_COEFFICIENT(z) (z + 13500)
prefix, maybe shorten to COEFF
> +
> +#define MMC35240_OTP_START_ADDR 0x1B
> +
> enum mmc35240_resolution {
> MMC35240_16_BITS_SLOW = 0, /* 100 Hz */
> MMC35240_16_BITS_FAST, /* 200 Hz */
> @@ -102,6 +127,10 @@ struct mmc35240_data {
> struct mutex mutex;
> struct regmap *regmap;
> enum mmc35240_resolution res;
> +
> + /* OTP compensation */
> + int axis_coef[3];
> + int axis_scale[3];
> };
>
> static const int mmc35240_samp_freq[] = {100, 200, 333, 666};
> @@ -172,8 +201,9 @@ static int mmc35240_hw_set(struct mmc35240_data *data, bool set)
>
> static int mmc35240_init(struct mmc35240_data *data)
> {
> - int ret;
> + int ret, y_convert, z_convert;
> unsigned int reg_id;
> + u8 otp_data[6];
>
> ret = regmap_read(data->regmap, MMC35240_REG_ID, ®_id);
> if (ret < 0) {
> @@ -197,9 +227,30 @@ static int mmc35240_init(struct mmc35240_data *data)
> return ret;
>
> /* set default sampling frequency */
> - return regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
> - MMC35240_CTRL1_BW_MASK,
> - data->res << MMC35240_CTRL1_BW_SHIFT);
> + ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
> + MMC35240_CTRL1_BW_MASK,
> + data->res << MMC35240_CTRL1_BW_SHIFT);
> + if (ret < 0)
> + return ret;
> +
> + ret = regmap_bulk_read(data->regmap, MMC35240_OTP_START_ADDR,
> + (u8 *)otp_data, sizeof(otp_data));
> + if (ret < 0)
> + return ret;
> +
> + y_convert = OTP_CONVERT_Y(((otp_data[1] & 0x03) << 4) |
> + (otp_data[2] >> 4));
> + z_convert = OTP_CONVERT_Z(otp_data[3] & 0x3f);
> +
> + data->axis_coef[0] = X_COEFFICIENT(1);
> + data->axis_coef[1] = Y_COEFFICIENT(y_convert);
> + data->axis_coef[2] = Z_COEFFICIENT(z_convert);
> +
> + data->axis_scale[0] = 1;
> + data->axis_scale[1] = 1000;
> + data->axis_scale[2] = 10000;
> +
> + return 0;
> }
>
> static int mmc35240_take_measurement(struct mmc35240_data *data)
> @@ -286,6 +337,9 @@ static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index,
> default:
> return -EINVAL;
> }
> + /* apply OTP compensation */
> + *val = (*val) * data->axis_coef[index] / data->axis_scale[index];
> +
> return 0;
> }
>
>
--
Peter Meerwald
+43-664-2444418 (mobile)
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