drivers: sensor: add mcp970x thermistor IC

Add driver for:
  MCP9700/9700A and MCP9701/9701A
  Low-Power Linear Active Thermistor ICs

http://ww1.microchip.com/downloads/en/devicedoc/20001942g.pdf

Signed-off-by: Nick Ward <nix.ward@gmail.com>

drivers/sensor/CMakeLists.txt

@@ -74,6 +74,7 @@ add_subdirectory_ifdef(CONFIG_MAX31865		max31865)
 add_subdirectory_ifdef(CONFIG_MAX31875		max31875)
 add_subdirectory_ifdef(CONFIG_MAX44009		max44009)
 add_subdirectory_ifdef(CONFIG_MAX6675		max6675)
+add_subdirectory_ifdef(CONFIG_MCP970X		mcp970x)
 add_subdirectory_ifdef(CONFIG_MCP9808		mcp9808)
 add_subdirectory_ifdef(CONFIG_MHZ19B		mhz19b)
 add_subdirectory_ifdef(CONFIG_MPR			mpr)

drivers/sensor/Kconfig

@@ -191,6 +191,8 @@ source "drivers/sensor/max6675/Kconfig"
 
 source "drivers/sensor/mchp_tach_xec/Kconfig"
 
+source "drivers/sensor/mcp970x/Kconfig"
+
 source "drivers/sensor/mcp9808/Kconfig"
 
 source "drivers/sensor/mhz19b/Kconfig"

drivers/sensor/mcp970x/CMakeLists.txt

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_sources(mcp970x.c)

drivers/sensor/mcp970x/Kconfig

@@ -0,0 +1,13 @@
+# Microchip MCP970X ADC driver
+#
+# Copyright (c) 2023 FTP Technologies
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config MCP970X
+	bool "MCP9700/9700A and MCP9701/9701A sensor"
+	default y
+	depends on DT_HAS_MICROCHIP_MCP970X_ENABLED
+	select ADC
+	help
+	  Enables Low-Power Linear Active Thermistor IC driver.

drivers/sensor/mcp970x/mcp970x.c

@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2023 FTP Technologies
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT microchip_mcp970x
+
+#include <zephyr/drivers/adc.h>
+#include <zephyr/drivers/sensor.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(mcp970x, CONFIG_SENSOR_LOG_LEVEL);
+
+enum ic_family {
+	FAMILY_MCP9700_9700A,
+	FAMILY_MCP9701_9701A
+};
+
+/* Milli degrees C per degree C */
+#define MC_PER_C 1000
+
+#define MV_AT_0C_MCP9700_9700A 500
+#define MV_AT_0C_MCP9701_9701A 400
+
+#define T_COEFF_MCP9700_9700A 10
+#define T_COEFF_MCP9701_9701A 19.5
+
+struct mcp970x_config {
+	struct adc_dt_spec adc;
+	enum ic_family family;
+};
+
+struct mcp970x_data {
+	struct adc_sequence sequence;
+	int16_t raw;
+};
+
+static int fetch(const struct device *dev, enum sensor_channel chan)
+{
+	const struct mcp970x_config *config = dev->config;
+	struct mcp970x_data *data = dev->data;
+	int ret;
+
+	if ((chan != SENSOR_CHAN_AMBIENT_TEMP) && (chan != SENSOR_CHAN_ALL)) {
+		return -ENOTSUP;
+	}
+
+	ret = adc_read(config->adc.dev, &data->sequence);
+	if (ret != 0) {
+		LOG_ERR("adc_read: %d", ret);
+	}
+
+	return ret;
+}
+
+static int get(const struct device *dev, enum sensor_channel chan, struct sensor_value *val)
+{
+	const struct mcp970x_config *config = dev->config;
+	struct mcp970x_data *data = dev->data;
+	int32_t raw_val = data->raw;
+	int32_t t;
+	int ret;
+
+	__ASSERT_NO_MSG(val != NULL);
+
+	if (chan != SENSOR_CHAN_AMBIENT_TEMP) {
+		LOG_ERR("chan %d not supported", chan);
+		return -ENOTSUP;
+	}
+
+	ret = adc_raw_to_millivolts_dt(&config->adc, &raw_val);
+	if (ret != 0) {
+		LOG_ERR("to_mv: %d", ret);
+		return ret;
+	}
+
+	if (config->family == FAMILY_MCP9700_9700A) {
+		t = (MC_PER_C * (raw_val - MV_AT_0C_MCP9700_9700A)) / T_COEFF_MCP9700_9700A;
+	} else {
+		int32_t t_coeff = 10 * T_COEFF_MCP9701_9701A; /* float to int */
+
+		t = (MC_PER_C * 10 * (raw_val - MV_AT_0C_MCP9701_9701A)) / t_coeff;
+	}
+
+	val->val1 = t / MC_PER_C;
+	val->val2 = t  % (1000000 / MC_PER_C);
+
+	LOG_DBG("%d of %d, %dmV, %dmC", data->raw, (1 << data->sequence.resolution) - 1, raw_val,
+		t);
+
+	return 0;
+}
+
+static const struct sensor_driver_api mcp970x_api = {
+	.sample_fetch = fetch,
+	.channel_get = get,
+};
+
+static int init(const struct device *dev)
+{
+	const struct mcp970x_config *config = dev->config;
+	struct mcp970x_data *data = dev->data;
+	int ret;
+
+	if (!device_is_ready(config->adc.dev)) {
+		LOG_ERR("ADC is not ready");
+		return -ENODEV;
+	}
+
+	ret = adc_channel_setup_dt(&config->adc);
+	if (ret != 0) {
+		LOG_ERR("setup: %d", ret);
+		return ret;
+	}
+
+	ret = adc_sequence_init_dt(&config->adc, &data->sequence);
+	if (ret != 0) {
+		LOG_ERR("sequence: %d", ret);
+		return ret;
+	}
+
+	data->sequence.buffer = &data->raw;
+	data->sequence.buffer_size = sizeof(data->raw);
+
+	return 0;
+}
+
+#define MCP970X_INIT(inst)                                                                         \
+	static struct mcp970x_data mcp970x_##inst##_data = {0};                                    \
+                                                                                                   \
+	static const struct mcp970x_config mcp970x_##inst##_config = {                             \
+		.adc = ADC_DT_SPEC_INST_GET(inst),                                                 \
+		.family = DT_INST_ENUM_IDX(inst, family),                                          \
+	};                                                                                         \
+                                                                                                   \
+	SENSOR_DEVICE_DT_INST_DEFINE(inst, &init, NULL, &mcp970x_##inst##_data,                    \
+				     &mcp970x_##inst##_config, POST_KERNEL,                        \
+				     CONFIG_SENSOR_INIT_PRIORITY, &mcp970x_api);
+
+DT_INST_FOREACH_STATUS_OKAY(MCP970X_INIT)

dts/bindings/sensor/microchip,mcp970x.yaml

@@ -0,0 +1,28 @@
+#
+# Copyright (c) 2023 FTP Technologies
+#
+
+description: |
+    Microchip MCP9700/9700A MCP9701/9701A
+    Low-Power Linear Active Thermistor IC
+
+compatible: "microchip,mcp970x"
+
+include: sensor-device.yaml
+
+properties:
+  io-channels:
+    required: true
+    description: |
+      Channels available with this divider configuration.
+
+  family:
+    type: string
+    required: true
+    description: |
+      Family            Temperature Coefficient
+        MCP9700/9700A -   10.0mV
+        MCP9701/9701A -   19.5mV
+    enum:
+      - "MCP9700/9700A"
+      - "MCP9701/9701A"