boards/feather-m0: add arduino feature

boards/feather-m0/Kconfig

@@ -20,4 +20,5 @@ config BOARD_FEATHER_M0
     select HAS_PERIPH_TIMER
     select HAS_PERIPH_UART
     select HAS_PERIPH_USBDEV
+    select HAS_ARDUINO
     select HAS_HIGHLEVEL_STDIO

boards/feather-m0/Makefile.features

@@ -13,4 +13,5 @@ FEATURES_PROVIDED += periph_uart
 FEATURES_PROVIDED += periph_usbdev
 
 # Put other features for this board (in alphabetical order)
+FEATURES_PROVIDED += arduino
 FEATURES_PROVIDED += highlevel_stdio

boards/feather-m0/include/arduino_board.h

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2021 J. David Ibáñez <jdavid.ibp@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_feather-m0
+ * @{
+ *
+ * @file
+ * @brief       Board specific configuration for the Arduino API
+ *
+ * @author      J. David Ibáñez <jdavid.ibp@gmail.com>
+ */
+
+#ifndef ARDUINO_BOARD_H
+#define ARDUINO_BOARD_H
+
+#include "arduino_pinmap.h"
+#include "periph/pwm.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   The on-board LED is connected to pin 13 on this board
+ */
+#define ARDUINO_LED         (13)
+
+/**
+ * @brief   Look-up table for the Arduino's digital pins
+ */
+static const gpio_t arduino_pinmap[] = {
+    ARDUINO_PIN_0,
+    ARDUINO_PIN_1,
+    ARDUINO_PIN_2,
+    ARDUINO_PIN_3,
+    ARDUINO_PIN_4,
+    ARDUINO_PIN_5,
+    ARDUINO_PIN_6,
+    ARDUINO_PIN_7,
+    ARDUINO_PIN_8,
+    ARDUINO_PIN_9,
+    ARDUINO_PIN_10,
+    ARDUINO_PIN_11,
+    ARDUINO_PIN_12,
+    ARDUINO_PIN_13,
+    ARDUINO_PIN_14,
+    ARDUINO_PIN_15,
+    ARDUINO_PIN_16,
+    ARDUINO_PIN_17,
+    ARDUINO_PIN_18,
+    ARDUINO_PIN_19,
+    ARDUINO_PIN_20,
+    ARDUINO_PIN_21,
+    ARDUINO_PIN_22,
+    ARDUINO_PIN_23,
+    ARDUINO_PIN_24,
+};
+
+/**
+ * @brief   Look-up table for the Arduino's analog pins
+ */
+static const adc_t arduino_analog_map[] = {
+    ARDUINO_A0,
+    ARDUINO_A1,
+    ARDUINO_A2,
+    ARDUINO_A3,
+    ARDUINO_A4,
+    ARDUINO_A5,
+    ADC_UNDEF,
+    ARDUINO_A7,
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ARDUINO_BOARD_H */
+/** @} */

boards/feather-m0/include/arduino_pinmap.h

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2021 J. David Ibáñez <jdavid.ibp@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_feather-m0
+ * @{
+ *
+ * @file
+ * @brief       Mapping from MCU pins to Arduino pins
+ *
+ * You can use the defines in this file for simplified interaction with the
+ * Arduino specific pin numbers.
+ *
+ * @author      J. David Ibáñez <jdavid.ibp@gmail.com>
+ */
+
+#ifndef ARDUINO_PINMAP_H
+#define ARDUINO_PINMAP_H
+
+#include "periph/gpio.h"
+#include "periph/adc.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    Mapping of MCU pins to Arduino pins
+ *
+ * @{
+ */
+
+#define ARDUINO_PIN_0           GPIO_PIN(PA, 11) /**< D0 (RX) */
+#define ARDUINO_PIN_1           GPIO_PIN(PA, 10) /**< D1 (TX) */
+#define ARDUINO_PIN_2           GPIO_UNDEF       /**< D2 */
+#define ARDUINO_PIN_3           GPIO_UNDEF       /**< D3 */
+#define ARDUINO_PIN_4           GPIO_UNDEF       /**< D4 */
+#define ARDUINO_PIN_5           GPIO_PIN(PA, 15) /**< D5 */
+#define ARDUINO_PIN_6           GPIO_PIN(PA, 20) /**< D6 */
+#define ARDUINO_PIN_7           GPIO_UNDEF       /**< D7 */
+#define ARDUINO_PIN_8           GPIO_UNDEF       /**< D8 */
+#define ARDUINO_PIN_9           GPIO_PIN(PA, 7)  /**< D9 */
+#define ARDUINO_PIN_10          GPIO_PIN(PA, 18) /**< D10 */
+#define ARDUINO_PIN_11          GPIO_PIN(PA, 16) /**< D11 */
+#define ARDUINO_PIN_12          GPIO_PIN(PA, 19) /**< D12 */
+#define ARDUINO_PIN_13          GPIO_PIN(PA, 17) /**< D13 (LED) */
+#define ARDUINO_PIN_14          GPIO_PIN(PA, 2)  /**< D14 (A0) */
+#define ARDUINO_PIN_15          GPIO_PIN(PB, 8)  /**< D15 (A1) */
+#define ARDUINO_PIN_16          GPIO_PIN(PB, 9)  /**< D16 (A2) */
+#define ARDUINO_PIN_17          GPIO_PIN(PA, 4)  /**< D17 (A3) */
+#define ARDUINO_PIN_18          GPIO_PIN(PA, 5)  /**< D18 (A4) */
+#define ARDUINO_PIN_19          GPIO_PIN(PB, 2)  /**< D19 (A5) */
+#define ARDUINO_PIN_20          GPIO_PIN(PA, 22) /**< D20 (I2C SDA) */
+#define ARDUINO_PIN_21          GPIO_PIN(PA, 23) /**< D21 (I2C SCL) */
+#define ARDUINO_PIN_22          GPIO_PIN(PA, 12) /**< D22 (SPI MISO) */
+#define ARDUINO_PIN_23          GPIO_PIN(PB, 10) /**< D23 (SPI MOSI) */
+#define ARDUINO_PIN_24          GPIO_PIN(PB, 11) /**< D24 (SPI SCK) */
+
+#define ARDUINO_PIN_A0          ARDUINO_PIN_14   /**< A0 */
+#define ARDUINO_PIN_A1          ARDUINO_PIN_15   /**< A1 */
+#define ARDUINO_PIN_A2          ARDUINO_PIN_16   /**< A2 */
+#define ARDUINO_PIN_A3          ARDUINO_PIN_17   /**< A3 */
+#define ARDUINO_PIN_A4          ARDUINO_PIN_18   /**< A4 */
+#define ARDUINO_PIN_A5          ARDUINO_PIN_19   /**< A5 */
+#define ARDUINO_PIN_A7          ARDUINO_PIN_9    /**< A7 */
+/** @} */
+
+/**
+ * @name    Mapping of Arduino analog pins to RIOT ADC lines
+ * @{
+ */
+#define ARDUINO_A0              ADC_LINE(0)  /**< ADC 0 */
+#define ARDUINO_A1              ADC_LINE(2)  /**< ADC 1 */
+#define ARDUINO_A2              ADC_LINE(3)  /**< ADC 2 */
+#define ARDUINO_A3              ADC_LINE(4)  /**< ADC 3 */
+#define ARDUINO_A4              ADC_LINE(5)  /**< ADC 4 */
+#define ARDUINO_A5              ADC_LINE(10) /**< ADC 5 */
+#define ARDUINO_A7              ADC_LINE(7)  /**< ADC 7 */
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ARDUINO_PINMAP_H */
+/** @} */

sys/arduino/serialport.cpp

@@ -24,6 +24,7 @@ extern "C" {
 
 #include "fmt.h"
 #include "irq.h"
+#include "stdio_base.h"
 }
 
 #include "serialport.hpp"
@@ -41,19 +42,21 @@ SerialPort::SerialPort(uart_t dev)
 
 int SerialPort::available(void)
 {
-    return (int)rx_buf.avail;
+    return stdio_avail();
 }
 
 void SerialPort::begin(long baudrate)
 {
+    stdio_init();
     /* this clears the contents of the ringbuffer... */
-    ringbuffer_init(&rx_buf, rx_mem, SERIAL_RX_BUFSIZE);
-    uart_init(dev, (uint32_t)baudrate, rx_cb, (void *)&rx_buf);
+    stdio_clear();
+    (void)baudrate; // FIXME Should we use the baudrate, somehow?
 }
 
 void SerialPort::end(void)
 {
-    uart_poweroff(dev);
+    // XXX Should we switch off the stdio backend?
+    //uart_poweroff(dev);
 }
 
 size_t SerialPort::print(int val)
@@ -249,31 +252,32 @@ size_t SerialPort::println(void)
 
 int SerialPort::read(void)
 {
-    int res = -1;
-
-    irq_disable();
-    if (rx_buf.avail > 0) {
-        res = ringbuffer_get_one(&rx_buf);
+    if (stdio_avail()) {
+        char c;
+        ssize_t n = stdio_read((void*)&c, 1);
+        if (n != 1) {
+            return -1;
+        }
+        return c;
     }
-    irq_enable();
 
-    return res;
+    return -1;
 }
 
 int SerialPort::write(int val)
 {
-    uart_write(dev, (uint8_t *)&val, 1);
+    stdio_write((const void*)&val, 1);
     return 1;
 }
 
 int SerialPort::write(const char *str)
 {
-    uart_write(dev, (uint8_t *)str, strlen(str));
+    stdio_write((const void*)str, strlen(str));
     return strlen(str);
 }
 
 int SerialPort::write(char *buf, int len)
 {
-    uart_write(dev, (uint8_t *)buf, len);
+    stdio_write((const void*)buf, len);
     return len;
 }

sys/include/stdio_base.h

@@ -34,6 +34,18 @@ extern "C" {
  */
 void stdio_init(void);
 
+/**
+ * @brief Get number of bytes available for reading.
+ *
+ * @return nr of available bytes
+ */
+int stdio_avail(void);
+
+/**
+ * @brief Clear the input buffer
+ */
+void stdio_clear(void);
+
 /**
  * @brief read @p len bytes from stdio uart into @p buffer
  *

sys/usb/usbus/cdc/acm/cdc_acm_stdio.c

@@ -51,6 +51,16 @@ void stdio_init(void)
 #endif
 }
 
+int stdio_avail(void)
+{
+    return tsrb_avail(&_cdc_stdio_isrpipe.tsrb);
+}
+
+void stdio_clear(void)
+{
+    tsrb_clear(&_cdc_stdio_isrpipe.tsrb);
+}
+
 ssize_t stdio_read(void* buffer, size_t len)
 {
     (void)buffer;