[PATCH v3 4/7] iio: chemical: bme680: Add support for preheat current

Vasileios Amoiridis
2024-11-02T13:13:30Z

Add functionality to inject a specified amount of current to the heating
plate before the start of the gas measurement to allow the sensor to reach
faster to the requested temperature.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
drivers/iio/chemical/bme680.h | 1 +
drivers/iio/chemical/bme680_core.c | 41 ++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+)

diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h
index a0a7794543c8..00ab89b3138b 100644
--- a/drivers/iio/chemical/bme680.h
+++ b/drivers/iio/chemical/bme680.h
@@ -42,6 +42,7 @@
#define BME680_RHRANGE_MASK GENMASK(5, 4)
#define BME680_REG_RES_HEAT_VAL 0x00
#define BME680_RSERROR_MASK GENMASK(7, 4)
+#define BME680_REG_IDAC_HEAT_0 0x50
#define BME680_REG_RES_HEAT_0 0x5A
#define BME680_REG_GAS_WAIT_0 0x64
#define BME680_ADC_GAS_RES GENMASK(15, 6)
diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 6df87383c243..6cc1cb9e0477 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -118,6 +118,7 @@ struct bme680_data {
u8 oversampling_temp;
u8 oversampling_press;
u8 oversampling_humid;
+ u8 preheat_curr_mA;
u16 heater_dur;
u16 heater_temp;

@@ -214,6 +215,12 @@ static const struct iio_chan_spec bme680_channels[] = {
},
},
IIO_CHAN_SOFT_TIMESTAMP(4),
+ {
+ .type = IIO_CURRENT,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+ .output = 1,
+ .scan_index = -1,
+ },
};

static int bme680_read_calib(struct bme680_data *data,
@@ -561,6 +568,12 @@ static u8 bme680_calc_heater_dur(u16 dur)
return durval;
}

+/* Taken from datasheet, section 5.3.3 */
+static u8 bme680_calc_heater_preheat_current(u8 curr)
+{
+ return 8 * curr - 1;
+}
+
static int bme680_set_mode(struct bme680_data *data, enum bme680_op_mode mode)
{
struct device *dev = regmap_get_device(data->regmap);
@@ -659,6 +672,20 @@ static int bme680_chip_config(struct bme680_data *data)
return 0;
}

+static int bme680_preheat_curr_config(struct bme680_data *data, u8 val)
+{
+ struct device *dev = regmap_get_device(data->regmap);
+ u8 heatr_curr;
+ int ret;
+
+ heatr_curr = bme680_calc_heater_preheat_current(val);
+ ret = regmap_write(data->regmap, BME680_REG_IDAC_HEAT_0, heatr_curr);
+ if (ret < 0)
+ dev_err(dev, "failed to write idac_heat_0 register\n");
+
+ return ret;
+}
+
static int bme680_gas_config(struct bme680_data *data)
{
struct device *dev = regmap_get_device(data->regmap);
@@ -687,6 +714,10 @@ static int bme680_gas_config(struct bme680_data *data)
return ret;
}

+ ret = bme680_preheat_curr_config(data, data->preheat_curr_mA);
+ if (ret)
+ return ret;
+
/* Enable the gas sensor and select heater profile set-point 0 */
ret = regmap_update_bits(data->regmap, BME680_REG_CTRL_GAS_1,
BME680_RUN_GAS_MASK | BME680_NB_CONV_MASK,
@@ -939,6 +970,15 @@ static int bme680_write_raw(struct iio_dev *indio_dev,

return bme680_chip_config(data);
}
+ case IIO_CHAN_INFO_PROCESSED:
+ {
+ switch (chan->type) {
+ case IIO_CURRENT:
+ return bme680_preheat_curr_config(data, (u8)val);
+ default:
+ return -EINVAL;
+ }
+ }
default:
return -EINVAL;
}
@@ -1074,6 +1114,7 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
data->oversampling_temp = 8; /* 8X oversampling rate */
data->heater_temp = 320; /* degree Celsius */
data->heater_dur = 150; /* milliseconds */
+ data->preheat_curr_mA = 0;

ret = regmap_write(regmap, BME680_REG_SOFT_RESET, BME680_CMD_SOFTRESET);
if (ret < 0)
--
2.43.0