cpu/nrf51: added I2C driver implementation

cpu/nrf51/include/periph_cpu.h

@@ -33,6 +33,30 @@ extern "C" {
 #define UART_IRQN           (UART0_IRQn)
 /** @} */
 
+/**
+ * @brief   Override I2C speed settings
+ * @{
+ */
+#define HAVE_I2C_SPEED_T
+typedef enum {
+    I2C_SPEED_LOW       = 0x01,                         /**< not supported */
+    I2C_SPEED_NORMAL    = TWI_FREQUENCY_FREQUENCY_K100, /**< 100kbit/s */
+    I2C_SPEED_FAST      = TWI_FREQUENCY_FREQUENCY_K400, /**< 400kbit/s */
+    I2C_SPEED_FAST_PLUS = 0x02,                         /**< not supported */
+    I2C_SPEED_HIGH      = 0x03,                         /**< not supported */
+} i2c_speed_t;
+/** @} */
+
+/**
+ * @brief   I2C (TWI) configuration options
+ */
+typedef struct {
+    NRF_TWI_Type *dev;          /**< hardware device */
+    uint8_t pin_scl;            /**< SCL pin */
+    uint8_t pin_sda;            /**< SDA pin */
+    uint8_t ppi;                /**< PPI channel to use */
+} i2c_conf_t;
+
 #ifdef __cplusplus
 }
 #endif

cpu/nrf51/periph/i2c.c

@@ -0,0 +1,224 @@
+/*
+ * Copyright (C) 2016 Freie Universität Berlin
+ *
+ * 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     cpu_nrf51
+ * @{
+ *
+ * @file
+ * @brief       Low-level I2C driver implementation
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "mutex.h"
+#include "assert.h"
+#include "periph/i2c.h"
+#include "periph_conf.h"
+
+#define ENABLE_DEBUG        (0)
+#include "debug.h"
+
+#ifdef I2C_NUMOF
+
+/**
+ * @brief   If any of the 4 lower bits are set, the speed value is invalid
+ */
+#define INVALID_SPEED_MASK  (0x0f)
+
+/**
+ * @brief   Initialized bus locks (we have a maximum of two devices...)
+ */
+static mutex_t locks[] = {
+    MUTEX_INIT,
+    MUTEX_INIT
+};
+
+static inline NRF_TWI_Type *dev(i2c_t bus)
+{
+    return i2c_config[bus].dev;
+}
+
+static int error(i2c_t bus)
+{
+    DEBUG("[i2c] error 0x%02x\n", (int)dev(bus)->ERRORSRC);
+    dev(bus)->ERRORSRC = (TWI_ERRORSRC_DNACK_Clear |
+                          TWI_ERRORSRC_ANACK_Clear |
+                          TWI_ERRORSRC_OVERRUN_Clear);
+    dev(bus)->EVENTS_ERROR = 0;
+    return -1;
+}
+
+static int write(i2c_t bus, uint8_t addr, const void *data, int len, int stop)
+{
+    uint8_t *buf = (uint8_t *)data;
+
+    assert((bus <= I2C_NUMOF) && (len > 0));
+    DEBUG("i2c: writing %i byte to the bus\n", len);
+
+    dev(bus)->ADDRESS = (addr & 0x7f);
+
+    for (int i = 0; i < len; i++) {
+        dev(bus)->TXD = *buf++;
+        dev(bus)->EVENTS_TXDSENT = 0;
+        dev(bus)->TASKS_STARTTX = 1;
+        while (!(dev(bus)->EVENTS_TXDSENT) && !(dev(bus)->EVENTS_ERROR)) {}
+        if (dev(bus)->EVENTS_ERROR) {
+            return error(bus);
+        }
+    }
+
+    if (stop) {
+        dev(bus)->EVENTS_STOPPED = 0;
+        dev(bus)->TASKS_STOP = 1;
+        while (!(dev(bus)->EVENTS_STOPPED) && !(dev(bus)->EVENTS_ERROR)) {}
+        if (dev(bus)->EVENTS_ERROR) {
+            return error(bus);
+        }
+    }
+
+    return len;
+}
+
+int i2c_init_master(i2c_t bus, i2c_speed_t speed)
+{
+    if (bus >= I2C_NUMOF) {
+        return -1;
+    }
+    if (speed & INVALID_SPEED_MASK) {
+        return -2;
+    }
+
+    /* power on the bus */
+    dev(bus)->POWER = TWI_POWER_POWER_Enabled;
+
+    /* pin configuration */
+    GPIO_BASE->PIN_CNF[i2c_config[bus].pin_scl] = (GPIO_PIN_CNF_DRIVE_S0D1 << GPIO_PIN_CNF_DRIVE_Pos);
+    GPIO_BASE->PIN_CNF[i2c_config[bus].pin_scl] = (GPIO_PIN_CNF_DRIVE_S0D1 << GPIO_PIN_CNF_DRIVE_Pos);
+
+    dev(bus)->PSELSCL = i2c_config[bus].pin_scl;
+    dev(bus)->PSELSDA = i2c_config[bus].pin_sda;
+
+    NRF_PPI->CHENCLR = (1 << i2c_config[bus].ppi);
+    NRF_PPI->CH[i2c_config[bus].ppi].EEP = (uint32_t)&dev(bus)->EVENTS_BB;
+
+    /* bus clock speed configuration */
+    dev(bus)->FREQUENCY = speed;
+    /* enable the device */
+    dev(bus)->ENABLE = TWI_ENABLE_ENABLE_Enabled;
+
+    return 0;
+}
+
+int i2c_acquire(i2c_t bus)
+{
+    assert(bus <= I2C_NUMOF);
+    mutex_lock(&locks[bus]);
+    return 0;
+}
+
+int i2c_release(i2c_t bus)
+{
+    assert(bus <= I2C_NUMOF);
+    mutex_unlock(&locks[bus]);
+    return 0;
+}
+
+int i2c_read_byte(i2c_t bus, uint8_t address, void *data)
+{
+    return i2c_read_bytes(bus, address, data, 1);
+}
+
+int i2c_read_bytes(i2c_t bus, uint8_t address, void *data, int length)
+{
+    uint8_t *in_buf = (uint8_t *)data;
+
+    assert((bus <= I2C_NUMOF) && (length > 0));
+    DEBUG("[i2c] reading %i byte from the bus\n", length);
+
+    /* set the client address */
+    dev(bus)->ADDRESS = (address & 0x7f);
+
+    /* setup PPI channel as alternative to the broken SHORTS
+     * -> see PAN notice #36: "Shortcuts described in nRF51 Reference Manual are
+     *                         not functional." */
+    if (length == 1) {
+        NRF_PPI->CH[i2c_config[bus].ppi].TEP = (uint32_t)&dev(bus)->TASKS_STOP;
+    }
+    else {
+        NRF_PPI->CH[i2c_config[bus].ppi].TEP = (uint32_t)&dev(bus)->TASKS_SUSPEND;
+    }
+    NRF_PPI->CHENSET = (1 << i2c_config[bus].ppi);
+
+    dev(bus)->EVENTS_RXDREADY = 0;
+    dev(bus)->EVENTS_STOPPED = 0;
+    dev(bus)->TASKS_STARTRX = 1;
+
+    for (int i = (length - 1); i >= 0; i--) {
+        while (!(dev(bus)->EVENTS_RXDREADY) && !(dev(bus)->EVENTS_ERROR)) {}
+        if (dev(bus)->EVENTS_ERROR) {
+            return error(bus);
+        }
+
+        *in_buf++ = (uint8_t)dev(bus)->RXD;
+
+        if (i == 1) {
+            NRF_PPI->CH[i2c_config[bus].ppi].TEP = (uint32_t)&dev(bus)->TASKS_STOP;
+        }
+
+        dev(bus)->EVENTS_RXDREADY = 0;
+        dev(bus)->TASKS_RESUME = 1;
+    }
+
+    /* wait for the device to finish up */
+    while (dev(bus)->EVENTS_STOPPED == 0) {}
+    NRF_PPI->CHENCLR = (1 << i2c_config[bus].ppi);
+
+    return length;
+}
+
+int i2c_read_reg(i2c_t bus, uint8_t address, uint8_t reg, void *data)
+{
+    write(bus, address, &reg, 1, 0);
+    return i2c_read_bytes(bus, address, data, 1);
+}
+
+int i2c_read_regs(i2c_t bus, uint8_t address, uint8_t reg,
+                  void *data, int length)
+{
+    write(bus, address, &reg, 1, 0);
+    return i2c_read_bytes(bus, address, data, length);
+}
+
+int i2c_write_byte(i2c_t bus, uint8_t address, uint8_t data)
+{
+    return write(bus, address, &data, 1, 1);
+}
+
+int i2c_write_bytes(i2c_t bus, uint8_t address, const void *data, int length)
+{
+    return write(bus, address, data, length, 1);
+}
+
+int i2c_write_reg(i2c_t bus, uint8_t address, uint8_t reg, uint8_t data)
+{
+    write(bus, address, &reg, 1, 0);
+    return write(bus, address, &data, 1, 1);
+}
+
+int i2c_write_regs(i2c_t bus, uint8_t address, uint8_t reg,
+                   const void *data, int length)
+{
+    write(bus, address, &reg, 1, 0);
+    return write(bus, address, data, length, 1);
+}
+
+#endif /* I2C_NUMOF */