Added 05-07 demos, challenges, and solutions. Updated README.

04-memory-allocation/esp32-freertos-04-demo-stack-overflow/esp32-freertos-04-demo-stack-overflow.ino

@@ -39,6 +39,7 @@ void testTask(void *parameter) {
  // One way to prevent heap overflow is to check the malloc output
  if (ptr == NULL) {
  Serial.println("Not enough heap.");
+ vPortFree(NULL);
  } else {
 
  // Do something with the memory so it's not optimized out by the compiler
@@ -52,7 +53,7 @@ void testTask(void *parameter) {
  Serial.println(xPortGetFreeHeapSize());
 
  // Free up our allocated memory
- vPortFree(ptr);
+ //vPortFree(ptr);
 
  // Wait for a while
  vTaskDelay(100 / portTICK_PERIOD_MS);

06-mutex/esp32-freertos-06-challenge-task-parameters/esp32-freertos-06-challenge-task-parameters.ino

@@ -0,0 +1,90 @@
+/**
+ * FreeRTOS Mutex Challenge
+ * 
+ * Pass a parameter to a task using a mutex.
+ * 
+ * Date: January 20, 2021
+ * Author: Shawn Hymel
+ * License: 0BSD
+ */
+
+// You'll likely need this on vanilla FreeRTOS
+//#include semphr.h
+
+// Use only core 1 for demo purposes
+#if CONFIG_FREERTOS_UNICORE
+ static const BaseType_t app_cpu = 0;
+#else
+ static const BaseType_t app_cpu = 1;
+#endif
+
+// Pins (change this if your Arduino board does not have LED_BUILTIN defined)
+static const int led_pin = LED_BUILTIN;
+
+//*****************************************************************************
+// Tasks
+
+// Blink LED based on rate passed by parameter
+void blinkLED(void *parameters) {
+
+ // Copy the parameter into a local variable
+ int num = *(int *)parameters;
+
+ // Print the parameter
+ Serial.print("Received: ");
+ Serial.println(num);
+
+ // Configure the LED pin
+ pinMode(led_pin, OUTPUT);
+
+ // Blink forever and ever
+ while (1) {
+ digitalWrite(led_pin, HIGH);
+ vTaskDelay(num / portTICK_PERIOD_MS);
+ digitalWrite(led_pin, LOW);
+ vTaskDelay(num / portTICK_PERIOD_MS);
+ }
+}
+
+//*****************************************************************************
+// Main (runs as its own task with priority 1 on core 1)
+
+void setup() {
+
+ long int delay_arg;
+
+ // Configure Serial
+ Serial.begin(115200);
+
+ // Wait a moment to start (so we don't miss Serial output)
+ vTaskDelay(1000 / portTICK_PERIOD_MS);
+ Serial.println();
+ Serial.println("---FreeRTOS Mutex Challenge---");
+ Serial.println("Enter a number for delay (milliseconds)");
+
+ // Wait for input from Serial
+ while (Serial.available() <= 0);
+
+ // Read integer value
+ delay_arg = Serial.parseInt();
+ Serial.print("Sending: ");
+ Serial.println(delay_arg);
+
+ // Start task 1
+ xTaskCreatePinnedToCore(blinkLED,
+ "Blink LED",
+ 1024,
+ (void *)&delay_arg,
+ 1,
+ NULL,
+ app_cpu);
+
+ // Show that we accomplished our task of passing the stack-based argument
+ Serial.println("Done!");
+}
+
+void loop() {
+
+ // Do nothing but allow yielding to lower-priority tasks
+ vTaskDelay(1000 / portTICK_PERIOD_MS);
+}

07-semaphore/esp32-freertos-07-challenge-counting-semaphore/esp32-freertos-07-challenge-counting-semaphore.ino

@@ -35,7 +35,6 @@ static int buf[BUF_SIZE]; // Shared buffer
 static int head = 0; // Writing index to buffer
 static int tail = 0; // Reading index to buffer
 static SemaphoreHandle_t bin_sem; // Waits for parameter to be read
-static SemaphoreHandle_t mutex; // Lock access to buffer and Serial
 
 //*****************************************************************************
 // Tasks
@@ -93,7 +92,6 @@ void setup() {
 
  // Create mutexes and semaphores before starting tasks
  bin_sem = xSemaphoreCreateBinary();
- mutex = xSemaphoreCreateMutex();
 
  // Start producer tasks (wait for each to read argument)
  for (int i = 0; i < num_prod_tasks; i++) {

07-semaphore/esp32-freertos-07-demo-binary-semaphore/esp32-freertos-07-demo-binary-semaphore.ino

@@ -89,7 +89,7 @@ void setup() {
  app_cpu);
 
  // Do nothing until binary semaphore has been returned
- while (xSemaphoreTake(bin_sem, 0) != pdTRUE);
+ xSemaphoreTake(bin_sem, portMAX_DELAY);
 
  // Show that we accomplished our task of passing the stack-based argument
  Serial.println("Done!");

README.md

@@ -6,18 +6,21 @@ Welcome to the demo code and solutions section of my Introduction to RTOS course
 
 This course is hosted on YouTube that you may take for free. All you need to do is watch the videos and complete the challenge issued at the end of each video. I highly recommend you try each challenge before peeking at the solutions here.
 
-The first video in the series is found here: %%%TODO: LINK%%%
+The first video in the series is found here: [Introduction to RTOS Part 1 - What is a Real-Time Operating System (RTOS)?](https://www.youtube.com/watch?v=F321087yYy4)
 
 Written guides that explain the solutions can be found [among my maker.io projects](https://www.digikey.com/en/maker/profiles/72825bdd887a427eaf8d960b6505adac).
 
 ## Directory Structure
 
 Examples and solutions are housed in dirctories that correspond to each chapter or video number. For example, if you watch "Intro to RTOS Part 3 - Task Scheduling," you should refer to the directory *03-task-scheduling-and-management.* In it, you will find 2 directories, one marked "demo" that gives the finished demo code used during the video (so you may run it and examine it at your own pace) and another marked "solution" that provides one possible solution to the challenge issued at the end of the video.
 
+If a challenge is issued in a video that starts with some code, it will be listed as a *challenge* Arduino sketch in the naming scheme shown below.
+
 Directories are in the following structure (where xx is the part or chapter number):
 
 ```
 xx-<name of chapter>
+|- esp32-freertos-xx-challenge-<name>
 |- esp32-freertos-xx-demo-<name>
 |- esp32-freertos-xx-solution-<name>
 ```