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.h

@@ -0,0 +1,126 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include "upm.h"
+#include "mraa/uart.h"
+#include "mraa/gpio.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+  /**
+   * @brief UPM C API for the DFRobot VK2828U7 GPS Module
+   *
+   * The driver was tested with the DFRobot VK2828U7 GPS Module.  It
+   * is accessed via a UART and provides NMEA data.
+   *
+   * @snippet vk2828u7.c Interesting
+   */
+  
+  /**
+   * Device context
+   */
+  typedef struct _vk2828u7_context {
+    mraa_uart_context        uart;
+    mraa_gpio_context        gpio_en;
+  } *vk2828u7_context;
+  
+  /**
+   * VK2828U7 Initializer
+   *
+   * @param uart Specify which uart to use.
+   * @param baudrate Specify the baudrate to use.  The device defaults
+   * to 9600 baud.
+   * @param enable_pin Specify the GPIO pin to use for the enable pin,
+   * -1 to not use an enable pin.
+   * @return an initialized device context on success, NULL on error.
+   */
+  vk2828u7_context vk2828u7_init(unsigned int uart, unsigned int baudrate,
+                                 int enable_pin);
+
+  /**
+   * VK2828U7 sensor close function
+   */
+  void vk2828u7_close(vk2828u7_context dev);
+
+  /**
+   * Read character data from the device.
+   *
+   * @param dev sensor context
+   * @param buffer The character buffer to read data into.
+   * @param len The maximum size of the buffer
+   * @return The number of bytes successfully read, or -1 on error
+   */
+  int vk2828u7_read(const vk2828u7_context dev, char *buffer, size_t len);
+
+  /**
+   * Write character data to the device.
+   *
+   * @param dev sensor context
+   * @param buffer The character buffer containing data to write.
+   * @param len The number of bytes to write.
+   * @return The number of bytes successfully written, or -1 on error.
+   */
+  int vk2828u7_write(const vk2828u7_context dev, char *buffer, size_t len);
+
+  /**
+   * Enable or disable the device.  When disabled, the device enters a
+   * low power mode and does not emit NMEA data.  It will still
+   * maintain location data however.
+   *
+   * @param dev sensor context
+   * @param enable true to enable the device, false otherwise.
+   * @return UPM result
+   */
+  upm_result_t vk2828u7_enable(const vk2828u7_context dev, bool enable);
+
+  /**
+   * Set the baudrate of the device.  By default, vk2828u7_init() will
+   * set the baudrate to 9600.
+   *
+   * @param dev sensor context
+   * @param baudrate The baud rate to set for the device.
+   * @return UPM result
+   */
+  upm_result_t vk2828u7_set_baudrate(const vk2828u7_context dev,
+                                     unsigned int baudrate);
+
+  /**
+   * Determine whether there is data available to be read.
+   *
+   * @param dev sensor context
+   * @param millis The number of milliseconds to wait for data to
+   * become available.
+   * @return true if data is available to be read, false otherwise.
+   */
+  bool vk2828u7_data_available(const vk2828u7_context dev,
+                               unsigned int millis);
+
+#ifdef __cplusplus
+}
+#endif