Added some examples

Based on examples from:
https://github.com/greiman/FreeRTOS-Arduino


Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

examples/frContextTime/frContextTime.ino

@@ -0,0 +1,72 @@
+// Test to determine context switch time with a semaphore
+// Connect a scope to LED_BUILTIN pin
+// Measure difference in time between first pulse with no context switch
+// and second pulse started in ledControl and ended in ledOffTask.
+// This is the time for the semaphore and a context switch.
+#include <STM32FreeRTOS.h>
+
+#define LED_PIN LED_BUILTIN
+// Semaphore to trigger context switch
+SemaphoreHandle_t xSemaphore;
+//------------------------------------------------------------------------------
+// high priority thread to set pin low
+static void ledOffTask(void *pvParameters) {
+  for (;;) {
+    xSemaphoreTake(xSemaphore, portMAX_DELAY);
+    digitalWrite(LED_PIN, LOW);
+  }
+}
+//------------------------------------------------------------------------------
+// lower priority thread to toggle LED and trigger thread 1
+static void ledControl(void *pvParameters) {
+  for (;;) {
+    // first pulse to get time with no context switch
+    digitalWrite(LED_PIN, HIGH);
+    digitalWrite(LED_PIN, LOW);
+
+    // start second pulse
+    digitalWrite(LED_PIN, HIGH);
+
+    // trigger context switch for task that ends pulse
+    xSemaphoreGive(xSemaphore);
+
+    // sleep until next tick
+    vTaskDelay(1);
+  }
+}
+//------------------------------------------------------------------------------
+void setup() {
+  Serial.begin(9600);
+  pinMode(LED_PIN, OUTPUT);
+
+  // create high priority thread
+  xTaskCreate(ledOffTask,
+    "Task1",
+    configMINIMAL_STACK_SIZE,
+    NULL,
+    tskIDLE_PRIORITY + 2,
+    NULL);
+
+  // create lower priority thread
+  xTaskCreate(ledControl,
+    "Task2",
+    configMINIMAL_STACK_SIZE,
+    NULL,
+    tskIDLE_PRIORITY + 1,
+    NULL);
+
+  // create semaphore
+  vSemaphoreCreateBinary(xSemaphore);
+
+  // start FreeRTOS
+  vTaskStartScheduler();
+
+  // should never return
+  Serial.println("Die");
+  while(1);
+}
+//------------------------------------------------------------------------------
+void loop() {
+  // Not used - idle loop has a very small, configMINIMAL_STACK_SIZE, stack
+  // loop must never block
+}

examples/frFifoDataLogger/frFifoDataLogger.ino

@@ -0,0 +1,184 @@
+// Data logger based on a FIFO to decouple SD write latency from data
+// acquisition.
+
+// The FIFO uses two semaphores to synchronize between tasks.
+
+#include <SPI.h>
+#include <STM32FreeRTOS.h>
+#include <SD.h>
+
+// interval between points in units of 1000 usec
+const uint16_t intervalTicks = 1;
+//------------------------------------------------------------------------------
+// SD file definitions
+const uint8_t sdChipSelect = SS;
+File file;
+//------------------------------------------------------------------------------
+// Fifo definitions
+
+// size of fifo in records
+const size_t FIFO_SIZE = 200;
+
+// count of data records in fifo
+SemaphoreHandle_t fifoData;
+
+// count of free buffers in fifo
+SemaphoreHandle_t fifoSpace;
+
+// data type for fifo item
+struct FifoItem_t {
+  uint32_t usec;
+  int value;
+  int error;
+};
+// array of data items
+FifoItem_t fifoArray[FIFO_SIZE];
+//------------------------------------------------------------------------------
+// handle for sensor task
+TaskHandle_t sens;
+static void Task1(void *arg) {
+  // index of record to be filled
+  size_t fifoHead = 0;
+
+  // count of overrun errors
+  int error = 0;
+
+  // dummy data
+  int count = 0;
+
+  // initialise the ticks variable with the current time.
+  TickType_t ticks = xTaskGetTickCount();
+
+  while (1) {
+    // wait until time for next data point
+    vTaskDelayUntil(&ticks, intervalTicks);
+
+    // get a buffer
+    if (xSemaphoreTake(fifoSpace, 0) != pdTRUE) {
+      // fifo full - indicate missed point
+      error++;
+      continue;
+    }
+    FifoItem_t* p = &fifoArray[fifoHead];
+    p->usec = micros();
+
+    // replace next line with data read from sensor
+    // f
+    p->value = count++;
+
+    p->error = error;
+    error = 0;
+
+    // signal new data
+    xSemaphoreGive(fifoData);
+
+    // advance FIFO index
+    fifoHead = fifoHead < (FIFO_SIZE - 1) ? fifoHead + 1 : 0;
+  }
+}
+//------------------------------------------------------------------------------
+// SD write task
+static void Task2(void *arg) {
+  // FIFO index for record to be written
+  size_t fifoTail = 0;
+
+  // time in micros of last point
+  uint32_t last = 0;
+
+  while(1) {
+    // wait for next data record
+    xSemaphoreTake(fifoData, portMAX_DELAY);
+
+    FifoItem_t* p = &fifoArray[fifoTail];
+
+    // print interval between points
+    if (last) {
+      file.print(p->usec - last);
+    } else {
+      file.write("NA");
+    }
+    last = p->usec;
+    file.write(',');
+    file.print(p->value);
+    file.write(',');
+    file.println(p->error);
+
+    // release record
+    xSemaphoreGive(fifoSpace);
+
+    // advance FIFO index
+    fifoTail = fifoTail < (FIFO_SIZE - 1) ? fifoTail + 1 : 0;
+
+    // check for end run
+    if (Serial.available()) {
+      // close file to insure data is saved correctly
+      file.close();
+
+      // print messages
+      Serial.println(F("Done"));
+      Serial.print(F("Task1 unused stack entries: "));
+      Serial.println(uxTaskGetStackHighWaterMark(sens));
+      Serial.print(F("Task2 unused stack entries: "));
+      Serial.println(uxTaskGetStackHighWaterMark(0));
+ //     ARM free heap not implemented yet
+ //     Serial.print(F("Free heap (bytes): "));
+ //     Serial.println(freeHeap());
+      while(1);
+    }
+  }
+}
+//------------------------------------------------------------------------------
+void setup() {
+  // task creation status
+  portBASE_TYPE s1, s2;
+
+  Serial.begin(9600);
+  while(!Serial);
+  Serial.println(F("Type any character to begin"));
+  while(!Serial.available());
+
+  // open file
+  if (!SD.begin(sdChipSelect)) {
+    Serial.println("Card failed, or not present");
+    // don't do anything more:
+    while(1);
+  }
+  Serial.println("card initialized.");
+
+  file = SD.open("DATA.CSV", FILE_WRITE);
+  if(!file) {
+    Serial.println("error opening DATA.CSV");
+    while(1);
+  }
+  // initialize fifoData semaphore to no data available
+  fifoData = xSemaphoreCreateCounting(FIFO_SIZE, 0);
+
+  // initialize fifoSpace semaphore to FIFO_SIZE free records
+  fifoSpace = xSemaphoreCreateCounting(FIFO_SIZE, FIFO_SIZE);
+
+  // create sensor task at priority two
+  s1 = xTaskCreate(Task1, NULL, configMINIMAL_STACK_SIZE, NULL, 2, &sens);
+
+  // create SD write task at priority one
+  s2 = xTaskCreate(Task2, NULL, configMINIMAL_STACK_SIZE + 200, NULL, 1, NULL);
+
+  // check for creation errors
+  if (fifoData == NULL || fifoSpace == NULL || s1 != pdPASS || s2 != pdPASS ) {
+    Serial.println(F("Creation problem"));
+    while(1);
+  }
+  // throw away serial input
+  while (Serial.available()) Serial.read();
+  Serial.println(F("Type any character to end"));
+
+  // start scheduler
+  vTaskStartScheduler();
+  Serial.println(F("Insufficient RAM"));
+  while(1);
+}
+//------------------------------------------------------------------------------
+// WARNING idle loop has a very small stack (configMINIMAL_STACK_SIZE)
+// loop must never block
+void loop() {
+  // not used
+}