Add nrf52 spi driver abstraction

include/spi.h

@@ -0,0 +1,29 @@
+#ifndef __NRF52_SPI_H__
+#define __NRF52_SPI_H__
+
+#include <stdint.h>
+
+#include "driver.h"
+
+int spi_open(const struct driver *drv);
+int spi_close(const struct driver *drv);
+
+int spi_read(const struct driver *drv, char *buffer, unsigned int len);
+int spi_write(const struct driver *drv, const char *buffer, unsigned int len);
+
+struct spi {
+    uint8_t sck_pin;
+    uint8_t mosi_pin;
+    uint8_t miso_pin;
+    uint8_t ss_pin;
+};
+
+static const struct driver_fp spi_fp = {
+    .open = spi_open,
+    .close = spi_close,
+    .read = spi_read,
+    .write = spi_write,
+    .ioctl = NULL
+};
+
+#endif

src/platform/nrf52/spi.c

@@ -0,0 +1,86 @@
+#include <assert.h>
+
+#include "nrf_drv_spi.h"
+#include "nrf_log.h"
+#include "nrf_log_ctrl.h"
+#include "nrf_log_default_backends.h"
+
+#include "driver.h"
+#include "spi.h"
+
+#define SPI_INSTANCE    0
+static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);
+static volatile bool spi_xfer_done;
+
+struct spi_object {
+    uint8_t *rx_buf;
+    uint8_t *tx_buf;
+    uint32_t rx_len;
+    uint32_t tx_len;
+};
+
+uint8_t rx_buffer[1];
+uint8_t tx_buffer[20];
+static struct spi_object spi_obj = {
+    .rx_buf = rx_buffer,
+    .tx_buf = tx_buffer,
+    .rx_len = sizeof(rx_buffer),
+    .tx_len = sizeof(tx_buffer)
+};
+
+void spi_event_handler(nrf_drv_spi_evt_t const * p_event, void * p_context)
+{
+    spi_xfer_done = true;
+    NRF_LOG_INFO("Transfer completed.");
+}
+
+int spi_open(const struct driver *drv)
+{
+    assert(NULL != drv);
+
+    struct spi *this = (struct spi *)(drv->dev);
+
+    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
+    spi_config.ss_pin = this->ss_pin;
+    spi_config.miso_pin = this->miso_pin;
+    spi_config.mosi_pin = this->mosi_pin;
+    spi_config.sck_pin  = this->sck_pin;
+    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));
+
+    return 0;
+}
+
+int spi_close(const struct driver *drv)
+{
+    assert(NULL != drv);
+
+    return 0;
+}
+
+int spi_read(const struct driver *drv, char *buffer, unsigned int len)
+{
+    assert((NULL != drv) && (NULL != buffer));
+
+    NRF_LOG_INFO("spi read not implemented yet.");
+
+    return 0;
+}
+
+int spi_write(const struct driver *drv, const char *buffer, unsigned int len)
+{
+    if(len > spi_obj.tx_len) {
+        NRF_LOG_ERROR("buffer too small");
+        return 0;
+    }
+    memcpy(spi_obj.tx_buf, buffer, len);
+
+    // Reset transfer done flag
+    spi_xfer_done = false;
+
+    APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, spi_obj.tx_buf, spi_obj.tx_len, spi_obj.rx_buf, spi_obj.rx_len));
+
+    while(!spi_xfer_done) {
+        __WFE();
+    }
+    return (int)len;
+}