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 v5 07/10] iio: afe: rescale: add RTD temperature sensor support
Date: Wed, 14 Jul 2021 23:12:12 -0400 [thread overview]
Message-ID: <20210715031215.1534938-8-liambeguin@gmail.com> (raw)
In-Reply-To: <20210715031215.1534938-1-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 4d3b44884a89..055f6b7c9869 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -356,10 +356,52 @@ 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[] = {
@@ -375,6 +417,10 @@ 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[] = {
@@ -384,6 +430,8 @@ 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
next prev parent reply other threads:[~2021-07-15 3:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 3:12 [PATCH v5 00/10] iio: afe: add temperature rescaling support Liam Beguin
2021-07-15 3:12 ` [PATCH v5 01/10] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-07-15 3:12 ` [PATCH v5 02/10] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-07-15 3:12 ` [PATCH v5 03/10] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-07-15 3:12 ` [PATCH v5 04/10] iio: afe: rescale: reduce risk of integer overflow Liam Beguin
2021-07-15 10:23 ` Peter Rosin
2021-07-16 16:46 ` Liam Beguin
2021-07-15 3:12 ` [PATCH v5 05/10] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-07-15 9:48 ` Peter Rosin
2021-07-16 19:18 ` Liam Beguin
2021-07-17 8:11 ` Peter Rosin
2021-07-17 16:55 ` Jonathan Cameron
2021-07-18 23:44 ` Liam Beguin
2021-07-19 8:31 ` Peter Rosin
2021-07-19 15:15 ` Liam Beguin
2021-07-15 3:12 ` [PATCH v5 06/10] iio: afe: rescale: add offset support Liam Beguin
2021-07-15 3:12 ` Liam Beguin [this message]
2021-07-15 3:12 ` [PATCH v5 08/10] iio: afe: rescale: add temperature transducers Liam Beguin
2021-07-15 3:12 ` [PATCH v5 09/10] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-07-15 3:12 ` [PATCH v5 10/10] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
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