Working DT ADC sample WITHOUT resistor divider

software/apps/adc_dt/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(ADC)
+
+target_sources(app PRIVATE src/main.c)

software/apps/adc_dt/README.rst

@@ -0,0 +1,62 @@
+.. zephyr:code-sample:: adc_dt
+   :name: Analog-to-Digital Converter (ADC) with devicetree
+   :relevant-api: adc_interface
+
+   Read analog inputs from ADC channels.
+
+Overview
+********
+
+This sample demonstrates how to use the :ref:`ADC driver API <adc_api>`.
+
+Depending on the target board, it reads ADC samples from one or more channels
+and prints the readings on the console. If voltage of the used reference can
+be obtained, the raw readings are converted to millivolts.
+
+The pins of the ADC channels are board-specific. Please refer to the board
+or MCU datasheet for further details.
+
+Building and Running
+********************
+
+The ADC peripheral and pinmux is configured in the board's ``.dts`` file. Make
+sure that the ADC is enabled (``status = "okay";``).
+
+In addition to that, this sample requires an ADC channel specified in the
+``io-channels`` property of the ``zephyr,user`` node. This is usually done with
+a devicetree overlay. The example overlay in the ``boards`` subdirectory for
+the ``nucleo_l073rz`` board can be easily adjusted for other boards.
+
+Configuration of channels (settings like gain, reference, or acquisition time)
+also needs to be specified in devicetree, in ADC controller child nodes. Also
+the ADC resolution and oversampling setting (if used) need to be specified
+there. See :zephyr_file:`boards/nrf52840dk_nrf52840.overlay
+<samples/drivers/adc/adc_dt/boards/nrf52840dk_nrf52840.overlay>` for an example of
+such setup.
+
+Building and Running for ST Nucleo L073RZ
+=========================================
+
+The sample can be built and executed for the
+:zephyr:board:`nucleo_l073rz` as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/drivers/adc/adc_dt
+   :board: nucleo_l073rz
+   :goals: build flash
+   :compact:
+
+To build for another board, change "nucleo_l073rz" above to that board's name
+and provide a corresponding devicetree overlay.
+
+Sample output
+=============
+
+You should get a similar output as below, repeated every second:
+
+.. code-block:: console
+
+   ADC reading:
+   - ADC_0, channel 7: 36 = 65mV
+
+.. note:: If the ADC is not supported, the output will be an error message.

software/apps/adc_dt/boards/weact_stm32g431_core.overlay

@@ -1,6 +1,7 @@
 / {
     zephyr,user {
-        io-channels = <&adc1 1>, <&adc1 12>;
+        io-channels = <&adc1 1>;
+        io-channel-names = "multi_sense";
     };
 };
 
@@ -16,19 +17,12 @@
     #address-cells = <1>;
     #size-cells = <0>;
 
-    channel@1 {
+    /* This defines channel 1 on adc1. The "1" in io-channels refers to this reg value. */
+    adc_channel_1: channel@1 {
         reg = <1>;
         zephyr,gain = "ADC_GAIN_1";
         zephyr,reference = "ADC_REF_INTERNAL";
         zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
         zephyr,resolution = <12>;
     };
-
-    channel@c {
-        reg = <0xc>;
-        zephyr,gain = "ADC_GAIN_1";
-        zephyr,reference = "ADC_REF_INTERNAL";
-        zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
-        zephyr,resolution = <12>;
-    };
 };

software/apps/adc_dt/prj.conf

@@ -0,0 +1,2 @@
+CONFIG_ADC=y
+CONFIG_LOG=y

software/apps/adc_dt/sample.yaml

@@ -0,0 +1,53 @@
+sample:
+  name: ADC devicetree driver sample
+tests:
+  sample.drivers.adc.adc_dt:
+    tags:
+      - adc
+    depends_on: adc
+    platform_allow:
+      - nucleo_l073rz
+      - disco_l475_iot1
+      - cc3220sf_launchxl
+      - cc3235sf_launchxl
+      - cy8cproto_063_ble
+      - stm32l496g_disco
+      - stm32h735g_disco
+      - nrf51dk/nrf51822
+      - nrf52840dk/nrf52840
+      - nrf54l15dk/nrf54l15/cpuapp
+      - nrf54h20dk/nrf54h20/cpuapp
+      - ophelia4ev/nrf54l15/cpuapp
+      - mec172xevb_assy6906
+      - gd32f350r_eval
+      - gd32f450i_eval
+      - gd32vf103v_eval
+      - gd32f403z_eval
+      - esp32_devkitc/esp32/procpu
+      - esp32s2_saola
+      - esp32c3_devkitm
+      - gd32l233r_eval
+      - lpcxpresso55s36
+      - mr_canhubk3
+      - longan_nano
+      - longan_nano/gd32vf103/lite
+      - rd_rw612_bga
+      - frdm_mcxn947/mcxn947/cpu0
+      - mcx_n9xx_evk/mcxn947/cpu0
+      - frdm_mcxc242
+      - ucans32k1sic
+      - xg24_rb4187c
+      - xg29_rb4412a
+      - raytac_an54l15q_db/nrf54l15/cpuapp
+      - frdm_mcxa166
+      - frdm_mcxa276
+    integration_platforms:
+      - nucleo_l073rz
+      - nrf52840dk/nrf52840
+    harness: console
+    timeout: 10
+    harness_config:
+      type: multi_line
+      regex:
+        - "ADC reading\\[\\d+\\]:"
+        - "- .+, channel \\d+: -?\\d+"

software/apps/adc_dt/socs/esp32_procpu.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022 Wolter HV <wolterhv@gmx.de>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>;
+	};
+};
+
+&adc0 {
+	status = "okay";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1_4";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

software/apps/adc_dt/socs/esp32c3.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022 Wolter HV <wolterhv@gmx.de>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>;
+	};
+};
+
+&adc0 {
+	status = "okay";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1_4";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

software/apps/adc_dt/socs/esp32s2.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022 Wolter HV <wolterhv@gmx.de>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>;
+	};
+};
+
+&adc0 {
+	status = "okay";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1_4";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

software/apps/adc_dt/socs/esp32s3_procpu.overlay

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022 Wolter HV <wolterhv@gmx.de>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>;
+	};
+};
+
+&adc0 {
+	status = "okay";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1_4";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

software/apps/adc_dt/src/main.c

@@ -1,101 +1,58 @@
-/*
+#include <zephyr/kernel.h>
- * Copyright (c) 2020 Libre Solar Technologies GmbH
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
-#include <inttypes.h>
-#include <stddef.h>
-#include <stdint.h>
-
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
 #include <zephyr/drivers/adc.h>
-#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
-#include <zephyr/sys/printk.h>
-#include <zephyr/sys/util.h>
 
-#if !DT_NODE_EXISTS(DT_PATH(zephyr_user)) || \
+LOG_MODULE_REGISTER(adc_dt_example, LOG_LEVEL_DBG);
-        !DT_NODE_HAS_PROP(DT_PATH(zephyr_user), io_channels)
-#error "No suitable devicetree overlay specified"
-#endif
 
-#define DT_SPEC_AND_COMMA(node_id, prop, idx) \
+/* Get the ADC channel specification from the devicetree */
-        ADC_DT_SPEC_GET_BY_IDX(node_id, idx),
+#define SENSE_NODE DT_PATH(zephyr_user)
-
+static const struct adc_dt_spec sense_channel = ADC_DT_SPEC_GET_BY_NAME(SENSE_NODE, multi_sense);
-/* Data of ADC io-channels specified in devicetree. */
-static const struct adc_dt_spec adc_channels[] = {
-        DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), io_channels,
-                             DT_SPEC_AND_COMMA)
-}; 
 
 int main(void)
 {
 	int err;
-	uint32_t count = 0;
 	uint16_t buf;
 	struct adc_sequence sequence = {
 		.buffer = &buf,
-		/* buffer size in bytes, not number of samples */
 		.buffer_size = sizeof(buf),
 	};
 
-	/* Configure channels individually prior to sampling. */
+	if (!device_is_ready(sense_channel.dev)) {
-	for (size_t i = 0U; i < ARRAY_SIZE(adc_channels); i++) {
+		LOG_ERR("ADC controller device not ready");
-		if (!adc_is_ready_dt(&adc_channels[i])) {
-			printk("ADC controller device %s not ready\n", adc_channels[i].dev->name);
 		return 0;
 	}
 
-		err = adc_channel_setup_dt(&adc_channels[i]);
+	err = adc_channel_setup_dt(&sense_channel);
 	if (err < 0) {
-			printk("Could not setup channel #%d (%d)\n", i, err);
+		LOG_ERR("Could not setup channel #%u (%d)", sense_channel.channel_id, err);
 		return 0;
 	}
-	}
 
-#ifndef CONFIG_COVERAGE
+	LOG_INF("ADC channel setup successful!");
+
 	while (1) {
-#else
+		// 1. Explicitly initialize the sequence structure from the devicetree spec.
-	for (int k = 0; k < 10; k++) {
+		// This sets sequence.channels correctly.
-#endif
+		(void)adc_sequence_init_dt(&sense_channel, &sequence);
-		printk("ADC reading[%u]:\n", count++);
-		for (size_t i = 0U; i < ARRAY_SIZE(adc_channels); i++) {
-			int32_t val_mv;
 
-			printk("- %s, channel %d: ",
+		// 2. Perform the read on the ADC device with the now-configured sequence.
-			       adc_channels[i].dev->name,
+		err = adc_read(sense_channel.dev, &sequence);
-			       adc_channels[i].channel_id);
-
-			(void)adc_sequence_init_dt(&adc_channels[i], &sequence);
-
-			err = adc_read_dt(&adc_channels[i], &sequence);
 		if (err < 0) {
-				printk("Could not read (%d)\n", err);
+			LOG_ERR("Could not read (%d)", err);
+			k_sleep(K_MSEC(1000));
 			continue;
 		}
 
-			/*
+		int32_t val_mv = buf;
-			 * If using differential mode, the 16 bit value
+		err = adc_raw_to_millivolts_dt(&sense_channel, &val_mv);
-			 * in the ADC sample buffer should be a signed 2's
-			 * complement value.
-			 */
-			if (adc_channels[i].channel_cfg.differential) {
-				val_mv = (int32_t)((int16_t)buf);
-			} else {
-				val_mv = (int32_t)buf;
-			}
-			printk("%"PRId32, val_mv);
-			err = adc_raw_to_millivolts_dt(&adc_channels[i],
-						       &val_mv);
-			/* conversion to mV may not be supported, skip if not */
 		if (err < 0) {
-				printk(" (value in mV not available)\n");
+			LOG_WRN("Could not convert to millivolts (%d)", err);
-			} else {
-				printk(" = %"PRId32" mV\n", val_mv);
-			}
 		}
 
+		LOG_INF("ADC reading raw: %d -> %d mV", buf, val_mv);
+
 		k_sleep(K_MSEC(1000));
 	}
 	return 0;