Reorganised GPS driver to allow for non-blocking acquisition of NMEA sentences

openrtx/include/core/gps.h

@@ -61,6 +61,6 @@ gps_t;
  * if available, enabled and ready, decode NMEA sentences and update
  * the radio state with the retrieved data.
  */
-void gps_taskFunc(char *line, int len);
+void gps_taskFunc(char *line);
 
 #endif /* GPS_H */

openrtx/include/interfaces/gps.h

@@ -36,6 +36,7 @@ extern "C" {
 /**
  * Initialise the GPS driver.
  * This function does not turn on the GPS module.
+ *
  * @param baud: baud rate of GPS serial interface.
  */
 void gps_init(const uint16_t baud);
@@ -58,19 +59,35 @@ void gps_disable();
 /**
  * Detect if a GPS module is present in the system, it can be called also
  * when driver is not initialised.
+ *
  * @param timeout: timeout for GPS detection, in milliseconds.
  * @return true if a GPS module is present, false otherwise.
  */
 bool gps_detect(uint16_t timeout);
 
 /**
- * Read a NMEA sentence from the GPS module, blocking function.
+ * Start the acquisition of a new NMEA sentence from the GPS module.
+ * The function returns immediately and acquisition is stopped when a complete
+ * sentence is received or maximum buffer length is reached.
+ *
  * @param buf: buffer to which the NMEA sentence is written.
  * @param maxLength: maximum writable length inside the buffer.
  * @return number of characters written in the buffer or -1 on error.
  */
 int gps_getNmeaSentence(char *buf, const size_t maxLength);
 
+/**
+ * Check if a newly acquired NMEA sentence is available.
+ *
+ * @return true if a NMEA sentence has been read from the GPS.
+ */
+bool gps_nmeaSentenceReady();
+
+/**
+ * Wait until a new NMEA sentence is ready, blocking the execution flow.
+ */
+void gps_waitForNmeaSentence();
+
 #ifdef __cplusplus
 }
 #endif

openrtx/src/core/gps.c

@@ -30,10 +30,8 @@
 /**
  * This function parses a GPS NMEA sentence and updates radio state
  */
-void gps_taskFunc(char *line, int len)
+void gps_taskFunc(char *line)
 {
-    (void) len;
-
     char nmea_id[3] = { 0 };
 
     // Little mechanism to ensure that RTC is synced with GPS time only once.

openrtx/src/core/threads.c

@@ -242,14 +242,16 @@ void *gps_task(void *arg)
 
     while(1)
     {
-        int len = gps_getNmeaSentence(line, MINMEA_MAX_LENGTH*10);
-        if(len != -1)
+        int status = gps_getNmeaSentence(line, MINMEA_MAX_LENGTH*10);
+        gps_waitForNmeaSentence();
+
+        if(status != -1)
         {
             // Lock mutex and update internal state
             pthread_mutex_lock(&state_mutex);
 
             // GPS readout is blocking, no need to delay here
-            gps_taskFunc(line, len);
+            gps_taskFunc(line);
 
             // Unlock state mutex
             pthread_mutex_unlock(&state_mutex);

platform/drivers/GPS/GPS_MDx.cpp

@@ -26,15 +26,14 @@
 #include <miosix.h>
 #include <kernel/scheduler/scheduler.h>
 
-int8_t  detectStatus = -1;
-size_t  bufPos = 0;
-size_t  maxPos = 0;
-char    *dataBuf;
-bool    receiving = false;
-uint8_t status = 0;
+static int8_t detectStatus = -1;
+static size_t bufPos = 0;
+static size_t maxPos = 0;
+static char   *dataBuf;
+static bool   receiving = false;
 
 using namespace miosix;
-Thread *gpsWaiting = 0;
+static Thread *gpsWaiting = 0;
 
 #ifdef PLATFORM_MD3x0
 #define PORT USART3
@@ -74,7 +73,8 @@ void __attribute__((used)) GpsUsartImpl()
 
         if((receiving == false) && (bufPos != 0))
         {
-            status = (bufPos < maxPos) ? 0x01 : 0x02;
+            // NMEA sentence received, turn off serial port
+            PORT->CR1 &= ~USART_CR1_UE;
 
             if(gpsWaiting)
             {
@@ -127,10 +127,8 @@ void gps_init(const uint16_t baud)
               | USART_CR1_RXNEIE;
 
     #ifdef PLATFORM_MD3x0
-    NVIC_ClearPendingIRQ(USART3_IRQn);
     NVIC_SetPriority(USART3_IRQn, 14);
     #else
-    NVIC_ClearPendingIRQ(USART1_IRQn);
     NVIC_SetPriority(USART1_IRQn, 14);
     #endif
 }
@@ -149,7 +147,15 @@ void gps_terminate()
 void gps_enable()
 {
     gpio_setPin(GPS_EN);
-    PORT->CR1 |= USART_CR1_UE;
+
+    // Enable IRQ
+    #ifdef PLATFORM_MD3x0
+    NVIC_ClearPendingIRQ(USART3_IRQn);
+    NVIC_EnableIRQ(USART3_IRQn);
+    #else
+    NVIC_ClearPendingIRQ(USART1_IRQn);
+    NVIC_EnableIRQ(USART1_IRQn);
+    #endif
 }
 
 void gps_disable()
@@ -162,6 +168,9 @@ void gps_disable()
     #else
     NVIC_DisableIRQ(USART1_IRQn);
     #endif
+
+    receiving = false;
+    bufPos    = 0;
 }
 
 bool gps_detect(uint16_t timeout)
@@ -199,16 +208,23 @@ int gps_getNmeaSentence(char *buf, const size_t maxLength)
     if(detectStatus != 1) return -1;
 
     memset(buf, 0x00, maxLength);
-    bufPos = 0;
-    maxPos = maxLength;
+    bufPos  = 0;
+    maxPos  = maxLength;
     dataBuf = buf;
 
-    #ifdef PLATFORM_MD3x0
-    NVIC_EnableIRQ(USART3_IRQn);
-    #else
-    NVIC_EnableIRQ(USART1_IRQn);
-    #endif
+    // Enable serial port
+    PORT->CR1 |= USART_CR1_UE;
 
+    return 0;
+}
+
+bool gps_nmeaSentenceReady()
+{
+    return (receiving == false) && (bufPos > 0);
+}
+
+void gps_waitForNmeaSentence()
+{
     /*
      * Put the calling thread in waiting status until a complete sentence is ready.
      */
@@ -222,20 +238,7 @@ int gps_getNmeaSentence(char *buf, const size_t maxLength)
                 FastInterruptEnableLock eLock(dLock);
                 Thread::yield();
             }
-        } while(gpsWaiting);
+        }
+        while(gpsWaiting);
     }
-
-    #ifdef PLATFORM_MD3x0
-    NVIC_DisableIRQ(USART3_IRQn);
-    #else
-    NVIC_DisableIRQ(USART1_IRQn);
-    #endif
-
-    if(status & 0x01)
-    {
-        return bufPos;
-    }
-
-    return -1;
 }
-

platform/drivers/GPS/GPS_linux.c

@@ -26,7 +26,8 @@
 #define MAX_NMEA_LEN 80
 #define NMEA_SAMPLES 8
 
-char test_nmea_sentences [NMEA_SAMPLES][MAX_NMEA_LEN] = {
+char test_nmea_sentences [NMEA_SAMPLES][MAX_NMEA_LEN] =
+{
     "$GPGGA,223659.522,5333.735,N,00959.130,E,1,12,1.0,0.0,M,0.0,M,,*62",
     "$GPGSA,A,3,01,02,03,04,05,06,07,08,09,10,11,12,1.0,1.0,1.0*30",
     "$GPGSV,3,1,12,30,79,066,27,05,63,275,21,07,42,056,,13,40,289,13*76",
@@ -36,28 +37,30 @@ char test_nmea_sentences [NMEA_SAMPLES][MAX_NMEA_LEN] = {
     "$GPVTG,92.15,T,,M,0.15,N,0.28,K,A*0C"
 };
 
-void gps_init(__attribute__((unused)) const uint16_t baud)
+void gps_init(const uint16_t baud)
 {
-    ;
+    (void) baud;
+    return;
 }
 
 void gps_terminate()
 {
-    ;
+    return;
 }
 
 void gps_enable()
 {
-    ;
+    return;
 }
 
 void gps_disable()
 {
-    ;
+    return;
 }
 
-bool gps_detect(__attribute__((unused)) uint16_t timeout)
+bool gps_detect(uint16_t timeout)
 {
+    (void) timeout;
     return true;
 }
 
@@ -77,3 +80,13 @@ int gps_getNmeaSentence(char *buf, const size_t maxLength)
     return len;
 }
 
+bool gps_nmeaSentenceReady()
+{
+    return true;
+}
+
+void gps_waitForNmeaSentence()
+{
+    return;
+}
+