zephyrCommon: Implement analogRead()/analogReference()

cores/arduino/Arduino.h

@@ -8,6 +8,7 @@
 
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/drivers/pwm.h>
+#include <zephyr/drivers/adc.h>
 #include <zephyr/kernel.h>
 
 #include <variants.h>

cores/arduino/zephyrCommon.cpp

@@ -6,13 +6,13 @@
 
 #include <Arduino.h>
 
-#define PWM_DT_SPEC(n,p,i) PWM_DT_SPEC_GET_BY_IDX(n, i),
-#define PWM_PINS(n,p,i) DT_PROP_BY_IDX(n, p, i),
-
 namespace {
 
 #ifdef CONFIG_PWM
 
+#define PWM_DT_SPEC(n,p,i) PWM_DT_SPEC_GET_BY_IDX(n, i),
+#define PWM_PINS(n,p,i) DT_PROP_BY_IDX(n, p, i),
+
 const struct pwm_dt_spec arduino_pwm[] =
 	{ DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), pwms, PWM_DT_SPEC) };
 
@@ -31,6 +31,33 @@ size_t pwm_pin_index(pin_size_t pinNumber) {
 
 #endif //CONFIG_PWM
 
+#ifdef CONFIG_ADC
+
+#define ADC_DT_SPEC(n,p,i) ADC_DT_SPEC_GET_BY_IDX(n, i),
+#define ADC_PINS(n,p,i) DT_PROP_BY_IDX(n, p, i),
+#define ADC_CH_CFG(n,p,i) arduino_adc[i].channel_cfg,
+
+const struct adc_dt_spec arduino_adc[] =
+  { DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), io_channels, ADC_DT_SPEC) };
+
+/* io-channel-pins node provides a mapping digital pin numbers to adc channels */
+const pin_size_t arduino_analog_pins[] =
+  { DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), io_channel_pins, ADC_PINS) };
+
+struct adc_channel_cfg channel_cfg[ARRAY_SIZE(arduino_analog_pins)] =
+  { DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), io_channels, ADC_CH_CFG) };
+
+size_t analog_pin_index(pin_size_t pinNumber) {
+  for(size_t i=0; i<ARRAY_SIZE(arduino_analog_pins); i++) {
+    if (arduino_analog_pins[i] == pinNumber) {
+      return i;
+    }
+  }
+  return (size_t)-1;
+}
+
+#endif //CONFIG_ADC
+
 }
 
 void yield(void) {
@@ -101,3 +128,56 @@ void analogWrite(pin_size_t pinNumber, int value)
 }
 
 #endif
+
+#ifdef CONFIG_ADC
+
+void analogReference(uint8_t mode)
+{
+  /*
+   * The Arduino API not clearly defined what means of
+   * the mode argument of analogReference().
+   * Treat the value as equivalent to zephyr's adc_reference.
+   */
+  size_t idx;
+  for (size_t i=0; i<ARRAY_SIZE(channel_cfg); i++) {
+    channel_cfg[i].reference = static_cast<adc_reference>(mode);
+  }
+}
+
+int analogRead(pin_size_t pinNumber)
+{
+  int err;
+  int16_t buf;
+  struct adc_sequence seq = { .buffer = &buf, .buffer_size = sizeof(buf) };
+  size_t idx = analog_pin_index(pinNumber);
+
+  if (idx >= ARRAY_SIZE(arduino_adc) ) {
+    return -EINVAL;
+  }
+
+  /*
+   * ADC that is on MCU supported by Zephyr exists
+   * only 16bit resolution, currently.
+   */
+  if (arduino_adc[idx].resolution > 16) {
+    return -ENOTSUP;
+  }
+
+  err = adc_channel_setup(arduino_adc[idx].dev, &arduino_adc[idx].channel_cfg);
+  if (err < 0) {
+    return err;
+  }
+
+  seq.channels = BIT(arduino_adc[idx].channel_id);
+  seq.resolution = arduino_adc[idx].resolution;
+  seq.oversampling = arduino_adc[idx].oversampling;
+
+  err = adc_read(arduino_adc[idx].dev, &seq);
+  if (err < 0) {
+    return err;
+  }
+
+  return buf;
+}
+
+#endif

samples/analog_input/CMakeLists.txt

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+set(DTC_OVERLAY_FILE $ENV{ZEPHYR_BASE}/../modules/lib/Arduino-Zephyr-API/variants/${BOARD}/${BOARD}.overlay)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(analog_input)
+
+target_sources(app PRIVATE src/main.cpp)
+zephyr_compile_options(-Wno-unused-variable -Wno-comment)

samples/analog_input/README.rst

@@ -0,0 +1,24 @@
+.. _analog_input:
+
+Analog Input
+############
+
+Overview
+********
+
+The analog_input sample blinks the LED with control of the period
+by the voltage of the input pin.
+Inputting high voltage to blink the LED slowly.
+Blink the LED fast on input voltage is low.
+When the input is 0V, LED light.
+
+Building and Running
+********************
+
+Build and flash analog_input sample as follows,
+
+```sh
+$> west build -p -b arduino_nano_33_ble sample/analog_input/
+
+$> west flash --bossac=/home/$USER/.arduino15/packages/arduino/tools/bossac/1.9.1-arduino2/bossac
+```

samples/analog_input/prj.conf

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

samples/analog_input/src/main.cpp

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2022 TOKITA Hiroshi <[email protected]>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <Arduino.h>
+
+const int analog_input = A0;    // select the input pin for the potentiometer
+const int ledPin = LED_BUILTIN;      // select the pin for the LED
+const float wait_factor = 1.f;
+
+void setup() {
+  pinMode(ledPin, OUTPUT);
+}
+
+void loop() {
+  int value = 0;
+
+  value = analogRead(analog_input);
+
+  /* Blinks slowly when the input voltage is high */
+
+  digitalWrite(ledPin, HIGH);
+  delay(value * wait_factor);
+
+  digitalWrite(ledPin, LOW);
+  delay(value * wait_factor);
+}

variants/arduino_mkrzero/arduino_mkrzero.overlay

@@ -3,6 +3,9 @@
  *
  * SPDX-License-Identifier: Apache-2.0
  */
+
+#include <zephyr/dt-bindings/adc/adc.h>
+
 / {
 	zephyr,user {
 		d0_gpios = <&arduino_mkr_header 0 0>;
@@ -27,27 +30,121 @@
 		d19_gpios = <&arduino_mkr_header 19 0>; /* D19 / A5 / I2C-SCL */
 		d20_gpios = <&arduino_mkr_header 20 0>;
 		d21_gpios = <&arduino_mkr_header 21 0>;
+
 		pwms =	<&tcc0 2 255>,
 			<&tcc0 3 255>;
 		pwm-pins = <2 3>;
+
+		io-channels =	<&adc 0>,
+				<&adc 10>,
+				<&adc 11>,
+				<&adc 4>,
+				<&adc 5>,
+				<&adc 6>,
+				<&adc 7>;
+		io-channel-pins = <15 16 17 18 19 20 21>;
 	};
 };
 
 &pinctrl {
-        pwm_default: pwm_default {
-                group1 {
-                        pinmux = <PA10F_TCC0_WO2>,
-                                 <PA11F_TCC0_WO3>;
-                };
-        };
+	pwm_default: pwm_default {
+		group1 {
+			pinmux = <PA10F_TCC0_WO2>,
+				 <PA11F_TCC0_WO3>;
+		};
+	};
+
+	adc_default: adc_default {
+		group1 {
+			pinmux = <PA2B_ADC_AIN0>,
+				 <PB2B_ADC_AIN10>,
+				 <PB3B_ADC_AIN11>,
+				 <PA4B_ADC_AIN4>,
+				 <PA5B_ADC_AIN5>,
+				 <PA6B_ADC_AIN6>,
+				 <PA7B_ADC_AIN7>;
+		};
+	};
 };
 
 &tcc0 {
-        status = "okay";
-        compatible = "atmel,sam0-tcc-pwm";
-        prescaler = <2>;
-        #pwm-cells = <2>;
+	status = "okay";
+	compatible = "atmel,sam0-tcc-pwm";
+	prescaler = <2>;
+	#pwm-cells = <2>;
+
+	pinctrl-0 = <&pwm_default>;
+	pinctrl-names = "default";
+};
+
+&adc {
+	status = "okay";
+	pinctrl-0 = <&adc_default>;
+	pinctrl-names = "default";
+
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <0>;
+	};
+
+	channel@4 {
+		reg = <4>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <4>;
+	};
+
+	channel@5 {
+		reg = <5>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <5>;
+	};
+
+	channel@6 {
+		reg = <6>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <6>;
+	};
+
+	channel@7 {
+		reg = <7>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <7>;
+	};
 
-        pinctrl-0 = <&pwm_default>;
-        pinctrl-names = "default";
+	channel@10 {
+		reg = <10>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <10>;
+	};
+
+	channel@11 {
+		reg = <11>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <10>;
+		zephyr,input-positive = <11>;
+	};
 };