samples: Add a sample SPI application

This application reads the 'WHO AM I' register from a LSM9DS0
sensor connected over SPI.

Change-Id: I7b0631e9bc783aea60fdb489f40058e0c15275fb
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

samples/nanokernel/apps/spi_lsm9ds0/Makefile

@@ -0,0 +1,5 @@
+KERNEL_TYPE = nano
+BOARD ?= qemu_x86
+CONF_FILE = prj.conf
+
+include ${ZEPHYR_BASE}/Makefile.inc

samples/nanokernel/apps/spi_lsm9ds0/README

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+SPI Test Application
+
+This application just retrieves the 'WHO AM I' register from the
+Accelerometer from a LSM9DS0 connected via API.
+
+The device datasheet can be found here:
+https://www.adafruit.com/datasheets/LSM9DS0.pdf
+
+Wiring information:
+
+| LSM9DS0 pin | Quark SE Devboard  |
+|             |	pin		   |
+|-------------+--------------------|
+| VIN         | VDD_HDR_3P3        |
+| CS_G        | GPIO24_SPI0_M_nCS0 |
+| CS_XM       | VDD_HDR_3P3        |
+| SCL         | GPIO24_SPI0_M_SCLK |
+| SDO_G       | GPIO24_SPI0_M_MISO |
+| SDO_XM      | Ground             |
+| SDA         | GPIO24_SPI0_M_MISO |
+| GND         | Ground             |

samples/nanokernel/apps/spi_lsm9ds0/prj.conf

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+CONFIG_SPI=y

samples/nanokernel/apps/spi_lsm9ds0/src/Makefile

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+obj-y += main.o

samples/nanokernel/apps/spi_lsm9ds0/src/main.c

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+/*
+ * Copyright (c) 2016 Intel Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <zephyr.h>
+
+#include <device.h>
+#include <spi.h>
+
+#include <misc/printk.h>
+
+#if defined(CONFIG_SPI_QMSI_PORT_0_DRV_NAME)
+#define SPI_PORT_0 CONFIG_SPI_QMSI_PORT_0_DRV_NAME
+#elif defined(CONFIG_SPI_DW_PORT_0_DRV_NAME)
+#define SPI_PORT_0 CONFIG_SPI_DW_PORT_0_DRV_NAME
+#else
+#error "Unknown SPI driver implementation"
+#endif
+
+#define LSM9DS0_WHOAMI_G 0xf
+#define LSM9DS0_READ_MASK 0x80
+
+static uint8_t rx_buffer[2], tx_buffer[2];
+
+static uint8_t lsm9ds0_read_whoami_g(struct device *dev)
+{
+	int err;
+
+	tx_buffer[1] = LSM9DS0_WHOAMI_G | LSM9DS0_READ_MASK;
+
+	err = spi_transceive(dev, tx_buffer, sizeof(tx_buffer),
+			     rx_buffer, sizeof(rx_buffer));
+	if (err) {
+		printk("Error during SPI transfer\n");
+		return 0;
+	}
+
+	return rx_buffer[0];
+}
+
+void main(void)
+{
+	struct spi_config config = { 0 };
+	struct device *spi_mst_0 = device_get_binding(SPI_PORT_0);
+	uint8_t id;
+	int err;
+
+	printk("SPI Example application\n");
+
+	if (!spi_mst_0)
+		return;
+
+	config.config = SPI_MODE_CPOL | SPI_MODE_CPHA | SPI_WORD(16);
+	config.max_sys_freq = 256;
+
+	err = spi_configure(spi_mst_0, &config);
+	if (err) {
+		printk("Could not configure SPI device\n");
+		return;
+	}
+
+	err = spi_slave_select(spi_mst_0, 1);
+	if (err) {
+		printk("Could not select SPI slave\n");
+		return;
+	}
+
+	id = lsm9ds0_read_whoami_g(spi_mst_0);
+
+	printk("LSM9DS0 Who Am I: 0x%x\n", id);
+}