nrf51: move common SPI implementation

cpu/nrf51/include/periph_cpu.h

@@ -94,6 +94,16 @@ typedef struct {
     i2c_speed_t speed;          /**< bus speed */
 } i2c_conf_t;
 
+/**
+ * @brief  SPI configuration values
+ */
+typedef struct {
+    NRF_SPI_Type *dev;  /**< SPI device used */
+    gpio_t sclk;        /**< CLK pin */
+    gpio_t mosi;        /**< MOSI pin */
+    gpio_t miso;        /**< MISO pin */
+} spi_conf_t;
+
 #ifdef __cplusplus
 }
 #endif

cpu/nrf51/periph/spi.c

@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2014-2016 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
+ * @ingroup     drivers_periph_spi
+ * @{
+ *
+ * @file
+ * @brief       Low-level SPI driver implementation
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Frank Holtz <frank-riot2015@holtznet.de>
+ * @author      Jan Wagner <mail@jwagner.eu>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "mutex.h"
+#include "assert.h"
+#include "periph/spi.h"
+#include "periph/gpio.h"
+
+/**
+ * @brief   array holding one pre-initialized mutex for each SPI device
+ */
+static mutex_t locks[SPI_NUMOF];
+
+static inline NRF_SPI_Type *dev(spi_t bus)
+{
+    return spi_config[bus].dev;
+}
+
+void spi_init(spi_t bus)
+{
+    assert(bus < SPI_NUMOF);
+
+    /* initialize mutex */
+    mutex_init(&locks[bus]);
+    /* initialize pins */
+    spi_init_pins(bus);
+}
+
+void spi_init_pins(spi_t bus)
+{
+    /* set pin direction */
+    gpio_init(spi_config[bus].sclk, GPIO_OUT);
+    gpio_init(spi_config[bus].mosi, GPIO_OUT);
+    gpio_init(spi_config[bus].miso, GPIO_IN);
+    /* select pins for the SPI device */
+    SPI_SCKSEL  = spi_config[bus].sclk;
+    SPI_MOSISEL = spi_config[bus].mosi;
+    SPI_MISOSEL = spi_config[bus].miso;
+}
+
+int spi_acquire(spi_t bus, spi_cs_t cs, spi_mode_t mode, spi_clk_t clk)
+{
+    (void) cs;
+
+    mutex_lock(&locks[bus]);
+    /* power on the bus (NRF51 only) */
+    dev(bus)->POWER = 1;
+    /* configure bus */
+    dev(bus)->CONFIG = mode;
+    dev(bus)->FREQUENCY = clk;
+    /* enable the bus */
+    dev(bus)->ENABLE = 1;
+
+    return SPI_OK;
+}
+
+void spi_release(spi_t bus)
+{
+    /* power off everything */
+    dev(bus)->ENABLE = 0;
+    dev(bus)->POWER = 0;
+    mutex_unlock(&locks[bus]);
+}
+
+void spi_transfer_bytes(spi_t bus, spi_cs_t cs, bool cont,
+                        const void *out, void *in, size_t len)
+{
+    const uint8_t *out_buf = out;
+    uint8_t *in_buf = in;
+
+    assert(out_buf || in_buf);
+
+    if (cs != SPI_CS_UNDEF) {
+        gpio_clear((gpio_t)cs);
+    }
+
+    for (int i = 0; i < (int)len; i++) {
+        uint8_t tmp = (out_buf) ? out_buf[i] : 0;
+
+        dev(bus)->EVENTS_READY = 0;
+        dev(bus)->TXD = (uint8_t)tmp;
+        while (dev(bus)->EVENTS_READY != 1);
+        tmp = (uint8_t)dev(bus)->RXD;
+
+        if (in_buf) {
+            in_buf[i] = tmp;
+        }
+    }
+
+    if ((cs != SPI_CS_UNDEF) && (!cont)) {
+        gpio_set((gpio_t)cs);
+    }
+}