iio:pressure:bmp280: fix pressure calculation

PATCH In review Hartmut Knaack 3 participants 3 messages Oct 31, 2014 – Nov 5, 2014 IIO

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Hartmut Knaack

author

2014-10-31 01:26 UTC #0 lore raw

PATCH 1/3 iio:pressure:bmp280: fix pressure calculation

According to the datasheet and as defined in struct bmp280_comp_press, dig_p1 is of type u16, while dig_p2 to dig_p9 are of type s16. In bmp280_read_compensation_press(), values read from the device were treated as the wrong type.
In bmp280_read_press() the fractional part of the measured pressure is calculated wrong. A better way is to use *val for the raw pressure and *val2 for the quotient and let the core do the proper conversion using IIO_VAL_FRACTIONAL.

Signed-off-by Hartmut Knaack <[email protected]>

---

drivers/iio/pressure/bmp280.c +12 ~~-12~~

index ce29ff9..75038da 100644
@@ -176,15 +176,15 @@ static int bmp280_read_compensation_press(struct bmp280_data *data,
 		return ret;
 	}
 
-	comp->dig_p1 = (s16) le16_to_cpu(buf[0]);
-	comp->dig_p2 = (u16) le16_to_cpu(buf[1]);
-	comp->dig_p3 = (u16) le16_to_cpu(buf[2]);
-	comp->dig_p4 = (u16) le16_to_cpu(buf[3]);
-	comp->dig_p5 = (u16) le16_to_cpu(buf[4]);
-	comp->dig_p6 = (u16) le16_to_cpu(buf[5]);
-	comp->dig_p7 = (u16) le16_to_cpu(buf[6]);
-	comp->dig_p8 = (u16) le16_to_cpu(buf[7]);
-	comp->dig_p9 = (u16) le16_to_cpu(buf[8]);
+	comp->dig_p1 = (u16) le16_to_cpu(buf[0]);
+	comp->dig_p2 = (s16) le16_to_cpu(buf[1]);
+	comp->dig_p3 = (s16) le16_to_cpu(buf[2]);
+	comp->dig_p4 = (s16) le16_to_cpu(buf[3]);
+	comp->dig_p5 = (s16) le16_to_cpu(buf[4]);
+	comp->dig_p6 = (s16) le16_to_cpu(buf[5]);
+	comp->dig_p7 = (s16) le16_to_cpu(buf[6]);
+	comp->dig_p8 = (s16) le16_to_cpu(buf[7]);
+	comp->dig_p9 = (s16) le16_to_cpu(buf[8]);
 
 	return 0;
 }

@@ -309,10 +309,10 @@ static int bmp280_read_press(struct bmp280_data *data,
 	adc_press = be32_to_cpu(tmp) >> 12;
 	comp_press = bmp280_compensate_press(data, &comp, adc_press);
 
-	*val = comp_press / 256000;
-	*val2 = comp_press * 1000000 / 256000;
+	*val = comp_press;
+	*val2 = 256000;
 
-	return IIO_VAL_INT_PLUS_MICRO;
+	return IIO_VAL_FRACTIONAL;
 }
 
 static int bmp280_read_raw(struct iio_dev *indio_dev,

Vlad Dogaru

Acked-by on v1 1/3

2014-10-31 11:42 UTC #1 lore raw

Quoted 9 lines · Hartmut Knaack

According to the datasheet and as defined in struct bmp280_comp_press, dig_p1 is of type u16, while dig_p2 to dig_p9 are of type s16. In bmp280_read_compensation_press(), values read from the device were treated as the wrong type.
In bmp280_read_press() the fractional part of the measured pressure is calculated wrong. A better way is to use *val for the raw pressure and *val2 for the quotient and let the core do the proper conversion using IIO_VAL_FRACTIONAL.
Signed-off-by Hartmut Knaack <[email protected]>

Acked-by Vlad Dogaru <[email protected]>

Jonathan Cameron

maintainer

2014-11-05 15:57 UTC #2 lore raw

Quoted 9 lines · Vlad Dogaru

Quoted 8 lines · Hartmut Knaack
According to the datasheet and as defined in struct bmp280_comp_press, dig_p1 is of type u16, while dig_p2 to dig_p9 are of type s16. In bmp280_read_compensation_press(), values read from the device were treated as the wrong type.
In bmp280_read_press() the fractional part of the measured pressure is calculated wrong. A better way is to use *val for the raw pressure and *val2 for the quotient and let the core do the proper conversion using IIO_VAL_FRACTIONAL.

Quoted 3 lines

Quoted 1 line
Signed-off-by Hartmut Knaack <[email protected]>
Acked-by Vlad Dogaru <[email protected]>

Applied to the togreg branch of iio.git - initially pushed out as testing for the autobuilders to play.

Thanks,

Jonathan

Quoted 5 lines

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