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From: Liam Beguin <liambeguin@gmail.com>
To: liambeguin@gmail.com, peda@axentia.se, jic23@kernel.org,
	lars@metafoo.de, pmeerw@pmeerw.net
Cc: linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
	devicetree@vger.kernel.org, robh+dt@kernel.org
Subject: [PATCH v7 10/13] iio: afe: rescale: add RTD temperature sensor support
Date: Sun,  1 Aug 2021 15:39:57 -0400	[thread overview]
Message-ID: <20210801194000.3646303-11-liambeguin@gmail.com> (raw)
In-Reply-To: <20210801194000.3646303-1-liambeguin@gmail.com>

From: Liam Beguin <lvb@xiphos.com>

An RTD (Resistance Temperature Detector) is a kind of temperature
sensor used to get a linear voltage to temperature reading within a
give range (usually 0 to 100 degrees Celsius). Common types of RTDs
include PT100, PT500, and PT1000.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 drivers/iio/afe/iio-rescale.c | 48 +++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index e37a9766080c..9683380aee5e 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -380,10 +380,52 @@ static int rescale_voltage_divider_props(struct device *dev,
 	return 0;
 }
 
+static int rescale_temp_sense_rtd_props(struct device *dev,
+					struct rescale *rescale)
+{
+	u32 factor;
+	u32 alpha;
+	u32 iexc;
+	u32 tmp;
+	int ret;
+	u32 r0;
+
+	ret = device_property_read_u32(dev, "excitation-current-microamp",
+				       &iexc);
+	if (ret) {
+		dev_err(dev, "failed to read excitation-current-microamp: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
+	if (ret) {
+		dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "r-naught-ohms", &r0);
+	if (ret) {
+		dev_err(dev, "failed to read r-naught-ohms: %d\n", ret);
+		return ret;
+	}
+
+	tmp = r0 * iexc * alpha / 1000000;
+	factor = gcd(tmp, 1000000);
+	rescale->numerator = 1000000 / factor;
+	rescale->denominator = tmp / factor;
+
+	rescale->offset = -1 * ((r0 * iexc) / 1000);
+
+	return 0;
+}
+
 enum rescale_variant {
 	CURRENT_SENSE_AMPLIFIER,
 	CURRENT_SENSE_SHUNT,
 	VOLTAGE_DIVIDER,
+	TEMP_SENSE_RTD,
 };
 
 static const struct rescale_cfg rescale_cfg[] = {
@@ -399,6 +441,10 @@ static const struct rescale_cfg rescale_cfg[] = {
 		.type = IIO_VOLTAGE,
 		.props = rescale_voltage_divider_props,
 	},
+	[TEMP_SENSE_RTD] = {
+		.type = IIO_TEMP,
+		.props = rescale_temp_sense_rtd_props,
+	},
 };
 
 static const struct of_device_id rescale_match[] = {
@@ -408,6 +454,8 @@ static const struct of_device_id rescale_match[] = {
 	  .data = &rescale_cfg[CURRENT_SENSE_SHUNT], },
 	{ .compatible = "voltage-divider",
 	  .data = &rescale_cfg[VOLTAGE_DIVIDER], },
+	{ .compatible = "temperature-sense-rtd",
+	  .data = &rescale_cfg[TEMP_SENSE_RTD], },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, rescale_match);
-- 
2.30.1.489.g328c10930387


  parent reply	other threads:[~2021-08-01 19:40 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-01 19:39 [PATCH v7 00/13] iio: afe: add temperature rescaling support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 01/13] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-08-01 19:39 ` [PATCH v7 02/13] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-08-01 19:39 ` [PATCH v7 03/13] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-08-01 19:39 ` [PATCH v7 04/13] iio: afe: rescale: expose scale processing function Liam Beguin
2021-08-01 19:39 ` [PATCH v7 05/13] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 06/13] iio: afe: rescale: add offset support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 07/13] iio: afe: rescale: reduce risk of integer overflow Liam Beguin
2021-08-01 19:39 ` [PATCH v7 08/13] iio: afe: rescale: fix precision on fractional log scale Liam Beguin
2021-08-02  9:17   ` Peter Rosin
2021-08-15 22:14     ` Liam Beguin
2021-08-01 19:39 ` [PATCH v7 09/13] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2021-08-01 19:39 ` Liam Beguin [this message]
2021-08-01 19:39 ` [PATCH v7 11/13] iio: afe: rescale: add temperature transducers Liam Beguin
2021-08-01 19:39 ` [PATCH v7 12/13] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-08-01 19:40 ` [PATCH v7 13/13] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin

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