vk2828u7: Initial implementation

This module provides support for the VK2828U7 (ublox based) GPS module
from DFRobot.  It is connected via a UART, and emits NMEA data.

Ideally this data could be fed to an external library like TinyGPS to
parse the NMEA data and provide an easier method of extracting GPS
information.

Signed-off-by: Jon Trulson <jtrulson@ics.com>

src/vk2828u7/vk2828u7.c

@@ -0,0 +1,151 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2016 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.
+ */
+
+#include <string.h>
+#include <assert.h>
+
+#include "vk2828u7.h"
+
+#include "upm_utilities.h"
+
+vk2828u7_context vk2828u7_init(unsigned int uart, unsigned int baudrate,
+                               int enable_pin)
+{
+  vk2828u7_context dev =
+    (vk2828u7_context)malloc(sizeof(struct _vk2828u7_context));
+
+  if (!dev)
+    return NULL;
+
+  // zero out context
+  memset((void *)dev, 0, sizeof(struct _vk2828u7_context));
+  
+  dev->uart = NULL;
+  dev->gpio_en = NULL;
+
+  // initialize the MRAA contexts
+
+  // uart, default should be 8N1
+  if (!(dev->uart = mraa_uart_init(uart)))
+    {
+      printf("%s: mraa_uart_init() failed.\n", __FUNCTION__);
+      vk2828u7_close(dev);
+      return NULL;
+    }
+
+  if (vk2828u7_set_baudrate(dev, baudrate))
+    {
+      printf("%s: vk2828u7_set_baudrate() failed.\n", __FUNCTION__);
+      vk2828u7_close(dev);
+      return NULL;
+    }      
+
+  mraa_uart_set_flowcontrol(dev->uart, false, false);
+
+  // now the gpio_en, if enabled
+  if (enable_pin >= 0)
+    {
+      if (!(dev->gpio_en = mraa_gpio_init(enable_pin)))
+        {
+          printf("%s: mraa_gpio_init() failed.\n", __FUNCTION__);
+          vk2828u7_close(dev);
+          return NULL;
+        }
+
+      mraa_gpio_dir(dev->gpio_en, MRAA_GPIO_OUT);
+
+      // wake up
+      vk2828u7_enable(dev, true);
+    }
+
+  return dev;
+}
+
+void vk2828u7_close(vk2828u7_context dev)
+{
+  assert(dev != NULL);
+
+  // sleepy-time
+  vk2828u7_enable(dev, false);
+
+  if (dev->uart)
+    mraa_uart_stop(dev->uart);
+  if (dev->gpio_en)
+    mraa_gpio_close(dev->gpio_en);
+
+  free(dev);
+}
+
+upm_result_t vk2828u7_enable(const vk2828u7_context dev, bool enable)
+{
+  assert(dev != NULL);
+
+  if (!dev->gpio_en)
+    return UPM_ERROR_NO_RESOURCES;
+
+  if (enable)
+    mraa_gpio_write(dev->gpio_en, 1);
+  else
+    mraa_gpio_write(dev->gpio_en, 0);
+
+  return UPM_SUCCESS;
+}
+
+int vk2828u7_read(const vk2828u7_context dev, char *buffer, size_t len)
+{
+  assert(dev != NULL);
+
+  return mraa_uart_read(dev->uart, buffer, len);
+}
+
+int vk2828u7_write(const vk2828u7_context dev, char *buffer, size_t len)
+{
+  assert(dev != NULL);
+
+  return mraa_uart_write(dev->uart, buffer, len);
+}
+
+bool vk2828u7_data_available(const vk2828u7_context dev, unsigned int millis)
+{
+  assert(dev != NULL);
+
+  if (mraa_uart_data_available(dev->uart, millis))
+    return true;
+  else
+    return false;
+}
+
+upm_result_t vk2828u7_set_baudrate(const vk2828u7_context dev,
+                                   unsigned int baudrate)
+{
+  assert(dev != NULL);
+
+  if (mraa_uart_set_baudrate(dev->uart, baudrate))
+    {
+      printf("%s: mraa_uart_set_baudrate() failed.\n", __FUNCTION__);
+      return UPM_ERROR_OPERATION_FAILED;
+    }      
+
+  return UPM_SUCCESS;
+}