cpu/atmega_common: add i2c periph driver

boards/arduino-atmega-common/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_i2c
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_uart

boards/arduino-atmega-common/include/periph_conf.h

@@ -143,6 +143,14 @@ extern "C" {
 #endif
 /** @} */
 
+/**
+ * @name    I2C configuration
+  * @{
+ */
+#define I2C_NUMOF           1
+#define I2C_0_EN            1
+#define I2C_IRQ_PRIO        1
+
 #ifdef __cplusplus
 }
 #endif

boards/waspmote-pro/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_i2c
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_uart

boards/waspmote-pro/include/periph_conf.h

@@ -104,6 +104,14 @@ extern "C" {
 #define MEGA_PRR            PRR0        /* Power Reduction Register */
 /** @} */
 
+/**
+ * @name    I2C configuration
+  * @{
+ */
+#define I2C_NUMOF           1
+#define I2C_0_EN            1
+#define I2C_IRQ_PRIO        1
+
 #ifdef __cplusplus
 }
 #endif

cpu/atmega_common/periph/i2c.c

+/*
+ * Copyright (C) 2017 Hamburg University of Applied Sciences, Dimitri Nahm
+ *
+ * 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.
+ */
+
+/**
+ * @addtogroup  driver_periph
+ * @{
+ *
+ * @file
+ * @brief       Low-level I2C driver implementation fot atmega common
+ *
+ * @note This implementation only implements the 7-bit addressing mode.
+ *
+ * @author      Dimitri Nahm <dimitri.nahm@haw-hamburg.de>
+ *
+ * @}
+ */
+
+#include <stdint.h>
+
+#include "cpu.h"
+#include "mutex.h"
+#include "periph/i2c.h"
+#include "periph_conf.h"
+
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+
+#define MT_START 0x08
+#define MT_ADDRESS_ACK 0x18
+#define MT_DATA_ACK 0x28
+#define MR_ADDRESS_ACK 0x40
+
+/* guard file in case no I2C device is defined */
+#if I2C_NUMOF
+
+/* static function definitions */
+static int _start(uint8_t address, uint8_t rw_flag);
+static int _write(const uint8_t *data, int length);
+static void _stop(void);
+
+/**
+ * @brief Array holding one pre-initialized mutex for each I2C device
+ */
+static mutex_t locks[] =  {
+#if I2C_0_EN
+    [I2C_0] = MUTEX_INIT,
+#endif
+};
+
+int i2c_init_master(i2c_t dev, i2c_speed_t speed)
+{
+    /* TWI Bit Rate Register - division factor for the bit rate generator*/
+    int twibrr;
+
+    /* check if the line is valid */
+    if (dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    /* calculate speed configuration */
+    switch (speed) {
+        case I2C_SPEED_NORMAL:
+            twibrr = ((CLOCK_CORECLOCK/100000)-16)/2;
+            break;
+
+        case I2C_SPEED_FAST:
+            twibrr = ((CLOCK_CORECLOCK/400000)-16)/2;
+            break;
+
+        default:
+            return -2;
+    }
+
+    /* set pull-up on SCL and SDA */
+    #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
+        PORTD |= (1 << PORTD0) | (1 << PORTD1);
+    #endif
+    #ifdef CPU_ATMEGA328P
+        PORTC |= (1 << PORTC4) | (1 << PORTC5);
+    #endif
+
+    /* enable I2C clock */
+    i2c_poweron(dev);
+
+    /* disable device */
+    TWCR &= ~(1 << TWEN);
+    /* configure I2C clock */
+    TWBR = twibrr;
+    /* enable device */
+    TWCR |= (1 << TWEN);
+
+    return 0;
+}
+
+int i2c_acquire(i2c_t dev)
+{
+    if (dev >= I2C_NUMOF) {
+        return -1;
+    }
+    mutex_lock(&locks[dev]);
+    return 0;
+}
+
+int i2c_release(i2c_t dev)
+{
+    if (dev >= I2C_NUMOF) {
+        return -1;
+    }
+    mutex_unlock(&locks[dev]);
+    return 0;
+}
+
+int i2c_read_byte(i2c_t dev, uint8_t address, void *data)
+{
+    return i2c_read_bytes(dev, address, data, 1);
+}
+
+int i2c_read_bytes(i2c_t dev, uint8_t address, void *data, int length)
+{
+    uint8_t *my_data = data;
+
+    if ((unsigned int)dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    /* send start condition and slave address */
+    if (_start(address, I2C_FLAG_READ) != 0)
+        return 0;
+
+    for (int i = 0; i < length; i++) {
+        /* Send NACK for last received byte */
+        if ((length-i) == 1)
+            TWCR = (1 << TWEN) | (1 << TWINT);
+        else
+            TWCR = (1 << TWEA) | (1 << TWEN) | (1 << TWINT);
+        DEBUG("Wait for byte %i\n", i+1);
+        /* Wait for TWINT Flag set. This indicates that DATA has been received.*/
+        while (!(TWCR & (1 << TWINT)))
+            {}
+        /* receive data byte */
+        my_data[i] = TWDR;
+        DEBUG("Byte %i received\n", i+1);
+    }
+
+    /* end transmission */
+    _stop();
+
+    return length;
+}
+
+int i2c_read_reg(i2c_t dev, uint8_t address, uint8_t reg, void *data)
+{
+    return i2c_read_regs(dev, address, reg, data, 1);
+}
+
+int i2c_read_regs(i2c_t dev, uint8_t address, uint8_t reg, void *data, int length)
+{
+    if ((unsigned int)dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    /* start transmission and send slave address */
+    if (_start(address, I2C_FLAG_WRITE) != 0)
+        return 0;
+
+    /* send register address and wait for complete transfer to be finished*/
+    if (_write(&reg, 1) != 1) {
+        _stop();
+        return 0;
+    }
+
+    _stop();
+
+    /* now start a new start condition and receive data */
+    return i2c_read_bytes(dev, address, data, length);
+}
+
+int i2c_write_byte(i2c_t dev, uint8_t address, uint8_t data)
+{
+    return i2c_write_bytes(dev, address, &data, 1);
+}
+
+int i2c_write_bytes(i2c_t dev, uint8_t address, const void *data, int length)
+{
+    int bytes = 0;
+
+    if ((unsigned int)dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    /* start transmission and send slave address */
+    if (_start(address, I2C_FLAG_WRITE) != 0)
+        return 0;
+
+    /* send out data bytes */
+    bytes = _write(data, length);
+
+    /* end transmission */
+    _stop();
+
+    return bytes;
+}
+
+int i2c_write_reg(i2c_t dev, uint8_t address, uint8_t reg, uint8_t data)
+{
+    if ((unsigned int)dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    return i2c_write_regs(dev, address, reg, &data, 1);
+}
+
+int i2c_write_regs(i2c_t dev, uint8_t address, uint8_t reg, const void *data, int length)
+{
+    int bytes = 0;
+
+    if ((unsigned int)dev >= I2C_NUMOF) {
+        return -1;
+    }
+
+    /* start transmission and send slave address */
+    if (_start(address, I2C_FLAG_WRITE) != 0)
+        return 0;
+    /* send register address and wait for complete transfer to be finished*/
+    if (_write(&reg, 1))
+        /* write data to register */
+        bytes = _write(data, length);
+    /* finish transfer */
+    _stop();
+    /* return number of bytes send */
+    return bytes;
+}
+
+void i2c_poweron(i2c_t dev)
+{
+    if (dev < I2C_NUMOF) {
+        #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
+            PRR0 &= ~(1 << PRTWI);
+        #endif
+        #ifdef CPU_ATMEGA328P
+            PRR &= ~(1 << PRTWI);
+        #endif
+    }
+}
+
+void i2c_poweroff(i2c_t dev)
+{
+    if (dev < I2C_NUMOF) {
+        #if defined (CPU_ATMEGA2560) || defined (CPU_ATMEGA1281)
+            PRR0 |= (1 << PRTWI);
+        #endif
+        #ifdef CPU_ATMEGA328P
+            PRR |= (1 << PRTWI);
+        #endif
+    }
+}
+
+static int _start(uint8_t address, uint8_t rw_flag)
+{
+    /* Reset I2C Interrupt Flag and transmit START condition */
+    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
+    DEBUG("START condition transmitted\n");
+
+    /* Wait for TWINT Flag set. This indicates that the START has been
+    transmitted, and ACK/NACK has been received.*/
+    while (!(TWCR & (1 << TWINT)))
+        {}
+
+    /* Check value of TWI Status Register. Mask prescaler bits.
+    If status different from START go to ERROR */
+    if ((TWSR & 0xF8) != MT_START) {
+        DEBUG("I2C Status Register is different from START\n");
+        _stop();
+        return -1;
+    }
+    else
+        DEBUG("I2C Status Register is: START\n");
+
+    /* Load ADDRESS and R/W Flag into TWDR Register.
+    Clear TWINT bit in TWCR to start transmission of ADDRESS */
+    TWDR = (address << 1) | rw_flag;
+    TWCR = (1 << TWINT) | (1 << TWEN);
+    DEBUG("ADDRESS and FLAG transmitted\n");
+
+    /* Wait for TWINT Flag set. This indicates that ADDRESS has been transmitted.*/
+    while (!(TWCR & (1 << TWINT)))
+        {}
+
+    /* Check value of TWI Status Register. Mask prescaler bits.
+    If status different from ADDRESS ACK go to ERROR */
+    if ((TWSR & 0xF8) == MT_ADDRESS_ACK)
+        DEBUG("ACK has been received for ADDRESS (write)\n");
+    else if ((TWSR & 0xF8) == MR_ADDRESS_ACK)
+        DEBUG("ACK has been received for ADDRESS (read)\n");
+    else {
+        DEBUG("NOT ACK has been received for ADDRESS\n");
+        _stop();
+        return -2;
+    }
+
+    return 0;
+}
+
+static int _write(const uint8_t *data, int length)
+{
+    int i = 0;
+
+    for (i = 0; i < length; i++) {
+        /* Load DATA into TWDR Register.
+        Clear TWINT bit in TWCR to start transmission of data */
+        TWDR = data[i];
+        TWCR = (1 << TWINT) | (1 << TWEN);
+        DEBUG("Byte %i transmitted\n", i+1);
+
+        /* Wait for TWINT Flag set. This indicates that DATA has been transmitted.*/
+        while (!(TWCR & (1 << TWINT)))
+            {}
+
+        /* Check value of TWI Status Register. Mask prescaler bits. If status
+        different from MT_DATA_ACK, return number of transmitted bytes */
+        if ((TWSR & 0xF8) != MT_DATA_ACK) {
+            DEBUG("NACK has been received for BYTE %i\n", i+1);
+            return i;
+        }
+        else
+            DEBUG("ACK has been received for BYTE %i\n", i+1);
+    }
+
+    return i;
+}
+
+static void _stop(void)
+{
+    /* Reset I2C Interrupt Flag and transmit STOP condition */
+    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
+    while (TWCR & (1 << TWSTO))
+        {}
+    DEBUG("STOP condition transmitted\n");
+    TWCR = 0;
+}
+
+#endif /* I2C_NUMOF */