samples: sensor: thermometer: update sample

Update thermometer sample with  mcp970x temperature sensor.

Removing test with frdm_k64f integration platform as it doesn't
provide an ambient temperature sensor.

Removing the bbc_microbit board as it only seems to provide the
die temperature of the nRF51 SoC and not an ambient temperature
sensor.

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

samples/sensor/thermometer/README.rst

@@ -1,4 +1,4 @@
-.. _thermometer-samples:
+.. _thermometer-sample:
 
 Thermometer sample
 ##################
@@ -6,26 +6,50 @@ Thermometer sample
 Overview
 ********
 
-A simple thermometer example, which writes the temperature to the console once per second.
+This sample application periodically measures the ambient temperature
+at 1Hz. The result is written to the console.
+
+Wiring
+*******
+
+VDD pin should be connected to 2.3V to 5.5V
+GND pin connected to 0V
+VOUT pin connected to the ADC input pin.
+
+.. _`MCP970X Sensor`: http://ww1.microchip.com/downloads/en/devicedoc/20001942g.pdf
+
+An overlay is provided for the nrf52840dk_nrf52840 board with the
+sensor connected to pin AIN7.
 
 Building and Running
 ********************
 
-It can be built and executed on bbc_microbit as follows:
+To build for the nrf52840dk_nrf52840 board use:
 
 .. zephyr-app-commands::
 	:zephyr-app: samples/sensor/thermometer
-	:board: bbc_microbit
-	:goals: build
+	:board: nrf52840dk_nrf52840
+	:goals: build flash
 	:compact:
 
+
+To build for other boards and ambient temperature sensors, enable the sensor
+node that supports ``SENSOR_CHAN_AMBIENT_TEMP`` and use an overlay to create an
+alias named ``ambient-temp0`` to link to the node.  See the overlay used for the
+``nrf52840dk_nrf52840`` board within this sample:
+``boards/nrf52840dk_nrf52840.overlay``
+
 Sample Output
 =============
 
 .. code-block:: console
 
-	Thermometer Example!
-	arm temp device is 0x20000184, name is TEMP_0
-	Temperature is 29.5C
-	Temperature is 29.5C
-	Temperature is 29.5C
+	*** Booting Zephyr OS build zephyr-v3.3.0-1205-g118f73e12a70 ***
+	Thermometer Example (arm)
+	Temperature device is 0x6150, name is mcp9700a
+	Temperature is 24.0°C
+	Temperature is 24.1°C
+	Temperature is 24.2°C
+	Temperature is 24.1°C
+	Temperature is 24.0°C
+	Temperature is 24.1°C

samples/sensor/thermometer/boards/nrf52840dk_nrf52840.overlay

@@ -0,0 +1,27 @@
+/ {
+	mcp9700a: mcp9700a {
+		status = "okay";
+		compatible = "microchip,mcp970x";
+		family = "MCP9700/9700A";
+		io-channels = <&adc 7>;
+	};
+
+	aliases {
+		ambient-temp0 = &mcp9700a;
+	};
+};
+
+&adc {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@7 {
+		reg = <7>;
+		zephyr,gain = "ADC_GAIN_1_3";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS,10)>;
+		zephyr,input-positive = <NRF_SAADC_AIN7>;
+		zephyr,resolution = <12>; /* 0.055C per ADC step */
+		zephyr,oversampling = <2>; /* x4 */
+	};
+};

samples/sensor/thermometer/sample.yaml

@@ -5,4 +5,5 @@ tests:
     tags: sensors
     harness: sensor
     integration_platforms:
-      - frdm_k64f
+      - nrf52840dk_nrf52840
+    platform_allow: nrf52840dk_nrf52840

samples/sensor/thermometer/src/main.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2016 ARM Ltd.
+ * Copyright (c) 2023 FTP Technologies
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -10,38 +11,33 @@
 
 void main(void)
 {
-	const struct device *temp_dev;
+	const struct device *const dev = DEVICE_DT_GET(DT_ALIAS(ambient_temp0));
+	struct sensor_value value;
+	int ret;
 
-	printf("Thermometer Example! %s\n", CONFIG_ARCH);
+	printf("Thermometer Example (%s)\n", CONFIG_ARCH);
 
-	temp_dev = device_get_binding("TEMP_0");
-	if (!temp_dev) {
-		printf("error: no temp device\n");
+	if (!device_is_ready(dev)) {
+		printf("Device %s is not ready\n", dev->name);
 		return;
 	}
 
-	printf("temp device is %p, name is %s\n",
-	       temp_dev, temp_dev->name);
+	printf("Temperature device is %p, name is %s\n", dev, dev->name);
 
 	while (1) {
-		int r;
-		struct sensor_value temp_value;
-
-		r = sensor_sample_fetch(temp_dev);
-		if (r) {
-			printf("sensor_sample_fetch failed return: %d\n", r);
+		ret = sensor_sample_fetch(dev);
+		if (ret != 0) {
+			printf("Sensor fetch failed: %d\n", ret);
 			break;
 		}
 
-		r = sensor_channel_get(temp_dev, SENSOR_CHAN_AMBIENT_TEMP,
-				       &temp_value);
-		if (r) {
-			printf("sensor_channel_get failed return: %d\n", r);
+		ret = sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &value);
+		if (ret != 0) {
+			printf("Sensor get failed: %d\n", ret);
 			break;
 		}
 
-		printf("Temperature is %gC\n",
-		       sensor_value_to_double(&temp_value));
+		printf("Temperature is %0.1lf°C\n", sensor_value_to_double(&value));
 
 		k_sleep(K_MSEC(1000));
 	}