drivers: sensors: Add support for RaspberryPi Pico CPU temperature

Support for the measuring the CPU die temperature
for the RaspberryPi Pico.

Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@fujitsu.com>

drivers/sensor/CMakeLists.txt

@@ -116,6 +116,7 @@ add_subdirectory_ifdef(CONFIG_TACH_IT8XXX2	ite_tach_it8xxx2)
 add_subdirectory_ifdef(CONFIG_VCMP_IT8XXX2	ite_vcmp_it8xxx2)
 add_subdirectory_ifdef(CONFIG_PCNT_ESP32	pcnt_esp32)
 add_subdirectory_ifdef(CONFIG_ESP32_TEMP	esp32_temp)
+add_subdirectory_ifdef(CONFIG_RPI_PICO_TEMP	rpi_pico_temp)
 
 if(CONFIG_USERSPACE OR CONFIG_SENSOR_SHELL OR CONFIG_SENSOR_SHELL_BATTERY)
 # The above if() is needed or else CMake would complain about

drivers/sensor/Kconfig

@@ -271,4 +271,6 @@ source "drivers/sensor/pcnt_esp32/Kconfig"
 
 source "drivers/sensor/esp32_temp/Kconfig"
 
+source "drivers/sensor/rpi_pico_temp/Kconfig"
+
 endif # SENSOR

drivers/sensor/rpi_pico_temp/CMakeLists.txt

@@ -0,0 +1,6 @@
+# Copyright (c) 2023 TOKITA Hiroshi
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_sources(rpi_pico_temp.c)

drivers/sensor/rpi_pico_temp/Kconfig

@@ -0,0 +1,13 @@
+# Raspberry Pi Pico temperature sensor configuration options
+
+# Copyright (c) 2023 TOKITA Hiroshi
+# SPDX-License-Identifier: Apache-2.0
+
+config RPI_PICO_TEMP
+	bool "Raspberry Pi Pico CPU Temperature Sensor"
+	default y
+	depends on DT_HAS_RASPBERRYPI_PICO_TEMP_ENABLED
+	depends on ADC
+
+	help
+	  Enable driver for Raspberry Pi Pico CPU temperature sensor.

drivers/sensor/rpi_pico_temp/rpi_pico_temp.c

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2023 TOKITA Hiroshi
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/sensor.h>
+#include <zephyr/drivers/adc.h>
+#include <zephyr/logging/log.h>
+
+#include <hardware/adc.h>
+
+LOG_MODULE_REGISTER(rpi_pico_temp, CONFIG_SENSOR_LOG_LEVEL);
+
+#define DT_DRV_COMPAT raspberrypi_pico_temp
+
+struct rpi_pico_temp_config {
+	const struct device *adc;
+	const struct adc_channel_cfg ch_cfg;
+	const int32_t vbe;
+	const int32_t vbe_slope;
+};
+
+struct rpi_pico_temp_data {
+	struct adc_sequence adc_seq;
+	int16_t sample;
+};
+
+static int rpi_pico_temp_sample_fetch(const struct device *dev, enum sensor_channel chan)
+{
+	const struct rpi_pico_temp_config *cfg = dev->config;
+	struct rpi_pico_temp_data *data = dev->data;
+	int rc;
+
+	if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_DIE_TEMP) {
+		return -ENOTSUP;
+	}
+
+	rc = adc_channel_setup(cfg->adc, &cfg->ch_cfg);
+	if (rc) {
+		LOG_DBG("Setup ADC channel %u failed with %d", cfg->ch_cfg.channel_id, rc);
+		return rc;
+	}
+
+	rc = adc_read(cfg->adc, &data->adc_seq);
+
+	return rc;
+}
+
+static int rpi_pico_temp_channel_get(const struct device *dev, enum sensor_channel chan,
+				     struct sensor_value *val)
+{
+	const struct rpi_pico_temp_config *cfg = dev->config;
+	struct rpi_pico_temp_data *data = dev->data;
+	int32_t mv = 0;
+	int32_t work;
+	int rc;
+
+	if (chan != SENSOR_CHAN_DIE_TEMP) {
+		return -ENOTSUP;
+	}
+
+	mv = data->sample;
+	rc = adc_raw_to_millivolts(adc_ref_internal(cfg->adc), cfg->ch_cfg.gain,
+				   data->adc_seq.resolution, &mv);
+	if (rc) {
+		LOG_DBG("adc_raw_to_millivolts() failed %d", rc);
+		return rc;
+	}
+
+	/*
+	 * Calculate CPU temperature from voltage by the equation:
+	 * T = 27 - (ADC_Voltage - 0.706)/0.001721
+	 */
+	work = ((27 * (-cfg->vbe_slope)) - (mv * 1000 - cfg->vbe));
+	val->val1 = work / (-cfg->vbe_slope);
+	work -= val->val1 * (-cfg->vbe_slope);
+	val->val2 = work * 1000000 / (-cfg->vbe_slope);
+
+	return 0;
+}
+
+static const struct sensor_driver_api rpi_pico_temp_driver_api = {
+	.sample_fetch = rpi_pico_temp_sample_fetch,
+	.channel_get = rpi_pico_temp_channel_get,
+};
+
+static int rpi_pico_temp_init(const struct device *dev)
+{
+	const struct rpi_pico_temp_config *cfg = dev->config;
+
+	if (!device_is_ready(cfg->adc)) {
+		LOG_ERR("Device %s is not ready", cfg->adc->name);
+		return -ENODEV;
+	}
+
+	adc_set_temp_sensor_enabled(true);
+
+	return 0;
+}
+
+#define RPI_PICO_TEMP_DEFINE(inst)                                                                 \
+	static const struct rpi_pico_temp_config rpi_pico_temp_config_##inst = {                   \
+		.adc = DEVICE_DT_GET(DT_INST_IO_CHANNELS_CTLR(inst)),                              \
+		.vbe = DT_INST_PROP(inst, vbe),                                                    \
+		.vbe_slope = DT_INST_PROP(inst, vbe_slope),                                        \
+		.ch_cfg =                                                                          \
+			{                                                                          \
+				.gain = ADC_GAIN_1,                                                \
+				.reference = ADC_REF_INTERNAL,                                     \
+				.acquisition_time = ADC_ACQ_TIME_DEFAULT,                          \
+				.channel_id = DT_INST_IO_CHANNELS_INPUT(inst),                     \
+				.differential = 0,                                                 \
+			},                                                                         \
+	};                                                                                         \
+	static struct rpi_pico_temp_data rpi_pico_temp_dev_data_##inst = {                         \
+		.adc_seq =                                                                         \
+			{                                                                          \
+				.channels = BIT(DT_INST_IO_CHANNELS_INPUT(inst)),                  \
+				.buffer = &rpi_pico_temp_dev_data_##inst.sample,                   \
+				.buffer_size = sizeof(rpi_pico_temp_dev_data_##inst.sample),       \
+				.resolution = 12U,                                                 \
+			},                                                                         \
+	};                                                                                         \
+                                                                                                   \
+	SENSOR_DEVICE_DT_INST_DEFINE(inst, rpi_pico_temp_init, NULL,                               \
+				     &rpi_pico_temp_dev_data_##inst, &rpi_pico_temp_config_##inst, \
+				     POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY,                     \
+				     &rpi_pico_temp_driver_api);
+
+DT_INST_FOREACH_STATUS_OKAY(RPI_PICO_TEMP_DEFINE)

dts/arm/rpi_pico/rp2040.dtsi

@@ -12,6 +12,10 @@
 #include "rpi_pico_common.dtsi"
 
 / {
+	aliases {
+		die-temp0 = &die_temp;
+	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -185,6 +189,12 @@
 	pinctrl: pin-controller {
 		compatible = "raspberrypi,pico-pinctrl";
 	};
+
+	die_temp: dietemp {
+		compatible = "raspberrypi,pico-temp";
+		io-channels = <&adc 4>;
+		status = "disabled";
+	};
 };
 
 &nvic {

dts/bindings/sensor/raspberrrypi,pico-temp.yaml

@@ -0,0 +1,35 @@
+# Copyright (c) 2023 TOKITA Hiroshi
+# SPDX-License-Identifier: Apache-2.0
+
+description: RaspberryPi Pico family temperature sensor node
+
+compatible: "raspberrypi,pico-temp"
+
+include: sensor-device.yaml
+
+properties:
+  io-channels:
+    required: true
+    description: ADC channel for CPU temperature sensor
+
+  vbe:
+    type: int
+    default: 706000
+    description: |
+      Vbe voltage in microvolts at 27 degrees C. Vbe = 0.706V typically.
+      The temperature sensor measures the Vbe voltage of a biased bipolar diode.
+      The temperature calculates from the Vbe voltage measured by the sensor
+      using the following equation typical case.
+
+        T = 27 - (ADC_Voltage - 0.706)/0.001721
+
+      See also the vbe-slope section.
+
+  vbe-slope:
+    type: int
+    default: -1721
+    description: |
+      The slope of Vbe voltage in microvolts per degree C.
+      Typically, a slope of -1.721mV per degree.
+
+      See also the vbe section.