examples: cleanup examples directory

Following changes are done as a part of cleanup:

1. Moved the platform specific `C` examples from top level examples/
directory to platform/ subdirectory and renamed helloedison.c to
gpio_edison.c

2. C specific examples are moved to a new c/ subdirectory. As a part
of this process, examples are modified to follow same standards
and few new examples are also added.

3. Include the newly added C examples to relevant API documentation

4. Ran clang-format for all source files in c/, c++/, platform/
subdirectories

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/c/spi.c

@@ -0,0 +1,154 @@
+/*
+ * Author: Michael Ring <mail@michael-ring.org>
+ * Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
+ * Contributors: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Example usage: Display set of patterns on MAX7219 repeately.
+ *                Press Ctrl+C to exit
+ */
+
+/* standard headers */
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* mraa header */
+#include "mraa/spi.h"
+
+/* SPI declaration */
+#define SPI_BUS 0
+
+/* SPI frequency in Hz */
+#define SPI_FREQ 400000
+
+uint16_t pat[] = { 0x01aa, 0x0255, 0x03aa, 0x0455, 0x05aa, 0x0655, 0x07aa, 0x0855 };
+uint16_t pat_inv[] = { 0x0155, 0x02aa, 0x0355, 0x04aa, 0x0555, 0x06aa, 0x0755, 0x08aa };
+uint16_t pat_clear[] = { 0x0100, 0x0200, 0x0300, 0x0400, 0x0500, 0x0600, 0x0700, 0x0800 };
+
+volatile sig_atomic_t flag = 1;
+
+void
+sig_handler(int signum)
+{
+    if (signum == SIGINT) {
+        fprintf(stdout, "Exiting...\n");
+        flag = 0;
+    }
+}
+
+int
+main(int argc, char** argv)
+{
+    mraa_result_t status = MRAA_SUCCESS;
+    mraa_spi_context spi;
+    int i, j;
+
+    /* initialize mraa for the platform (not needed most of the times) */
+    mraa_init();
+
+    //! [Interesting]
+    /* initialize SPI bus */
+    spi = mraa_spi_init(SPI_BUS);
+    if (spi == NULL) {
+        fprintf(stderr, "Failed to initialize SPI\n");
+        mraa_deinit();
+        return EXIT_FAILURE;
+    }
+
+    /* set SPI frequency */
+    status = mraa_spi_frequency(spi, SPI_FREQ);
+    if (status != MRAA_SUCCESS)
+        goto err_exit;
+
+    /* set big endian mode */
+    status = mraa_spi_lsbmode(spi, 0);
+    if (status != MRAA_SUCCESS) {
+        goto err_exit;
+    }
+
+    /* MAX7219/21 chip needs the data in word size */
+    status = mraa_spi_bit_per_word(spi, 16);
+    if (status != MRAA_SUCCESS) {
+        fprintf(stdout, "Failed to set SPI Device to 16Bit mode\n");
+        goto err_exit;
+    }
+
+    /* do not decode bits */
+    mraa_spi_write_word(spi, 0x0900);
+
+    /* brightness of LEDs */
+    mraa_spi_write_word(spi, 0x0a05);
+
+    /* show all scan lines */
+    mraa_spi_write_word(spi, 0x0b07);
+
+    /* set display on */
+    mraa_spi_write_word(spi, 0x0c01);
+
+    /* testmode off */
+    mraa_spi_write_word(spi, 0x0f00);
+
+    while (flag) {
+        /* set display pattern */
+        mraa_spi_write_buf_word(spi, pat, 16);
+
+        sleep(2);
+
+        /* set inverted display pattern */
+        mraa_spi_write_buf_word(spi, pat_inv, 16);
+
+        sleep(2);
+
+        /* clear the LED's */
+        mraa_spi_write_buf_word(spi, pat_clear, 16);
+
+        /* cycle through all LED's */
+        for (i = 1; i <= 8; i++) {
+            for (j = 0; j < 8; j++) {
+                mraa_spi_write_word(spi, (i << 8) + (1 << j));
+                sleep(1);
+            }
+            mraa_spi_write_word(spi, i << 8);
+        }
+    }
+
+    /* stop spi */
+    mraa_spi_stop(spi);
+
+    //! [Interesting]
+    /* deinitialize mraa for the platform (not needed most of the times) */
+    mraa_deinit();
+
+    return EXIT_SUCCESS;
+
+err_exit:
+    mraa_result_print(status);
+
+    /* stop spi */
+    mraa_spi_stop(spi);
+
+    /* deinitialize mraa for the platform (not needed most of the times) */
+    mraa_deinit();
+
+    return EXIT_FAILURE;
+}