From 6446f5209bfcebb1b9f8cc2e308cf6e0ba409ca4 Mon Sep 17 00:00:00 2001
From: Erick Ahmed <engineering@erickahmed.com>
Date: Tue, 16 Jun 2026 17:56:11 +0200
Subject: [PATCH] Remove semaphores in favor of task notifications

- Less overhead, simpler to manage
- Semaphores are apparently overkill for a simple blink timer
---
 Core/Inc/canlog.h |  1 -
 Core/Src/canlog.c | 27 +++++++++++++++++----------
 Core/Src/main.c   | 24 +++++++-----------------
 3 files changed, 24 insertions(+), 28 deletions(-)

diff --git a/Core/Inc/canlog.h b/Core/Inc/canlog.h
index 72ea736..4267270 100644
--- a/Core/Inc/canlog.h
+++ b/Core/Inc/canlog.h
@@ -44,7 +44,6 @@ typedef struct {
 
 typedef struct {
     LED_Config *led;
-    osSemaphoreId_t semaphore;
 } LEDContext;
 /* USER CODE END PTD */
 
diff --git a/Core/Src/canlog.c b/Core/Src/canlog.c
index b7ebeee..c5366ca 100644
--- a/Core/Src/canlog.c
+++ b/Core/Src/canlog.c
@@ -24,6 +24,9 @@
 extern CAN_HandleTypeDef hcan1;
 extern CAN_HandleTypeDef hcan2;
 
+extern osThreadId_t xLedTaskCAN1;
+extern osThreadId_t xLedTaskCAN2;
+
 /* Private function prototypes -----------------------------------------------*/
 /* USER CODE BEGIN FunctionPrototypes */
 /* BEGIN CAN_Logger_Init */
@@ -76,15 +79,17 @@ void HAL_CAN_RxFifo0MsgPendingCallback(CAN_HandleTypeDef *hcan)
     memcpy(message.payload, data, rxHeader.DLC);
 
     osMessageQueueId_t queue = (hcan->Instance == CAN1) ? xCAN1RxQueue : xCAN2RxQueue;
-    if (osMessageQueuePut(queue, &message, 0U, 0U) != osOK)
+    if (osMessageQueuePut(queue, &message, 0U, 0U) == osOK)
+    {
+      if (hcan->Instance == CAN1) osThreadFlagsSet(xLedTaskCAN1, 0x01);
+      else osThreadFlagsSet(xLedTaskCAN2, 0x01);
+    }
+    else
     {
         // TODO: better handling: flash error_led on osTimeout, call Error_Handler() when other errors
 
         // send errors like queue full via UART
     }
-
-    osSemaphoreId_t semaphore = (hcan->Instance == CAN1) ? xSemaphoreCAN1 : xSemaphoreCAN2;
-    osSemaphoreRelease(semaphore);
     /* CODE END */
 }
 /* END HAL_CAN_RxFifo0MsgPendingCallback */
@@ -126,12 +131,14 @@ void vLEDHeartbeat(void *argument)
     /* CODE BEGIN */
     LEDContext *context = (LEDContext*)argument;
 
-    for (;;)
-    {
-      if (osSemaphoreAcquire(context->semaphore, 25U) == osOK) HAL_GPIO_WritePin(context->led->port, context->led->pin, GPIO_PIN_SET);
-      else HAL_GPIO_WritePin(context->led->port, context->led->pin, GPIO_PIN_RESET);
-    }
-    /* CODE END */
+  for (;;)
+  {
+    uint32_t ret = osThreadFlagsWait(0x01, osFlagsWaitAny, 25U);
+
+    if (ret & 0x01) HAL_GPIO_WritePin(context->led->port, context->led->pin, GPIO_PIN_SET);
+    else HAL_GPIO_WritePin(context->led->port, context->led->pin, GPIO_PIN_RESET);
+  }
+  /* CODE END */
 }
 /* END vLEDHeartbeat */
 /* USER CODE END FunctionPrototypes */
diff --git a/Core/Src/main.c b/Core/Src/main.c
index 5e307f8..d0172f2 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -54,9 +54,6 @@ LED_Config led_error = {GPIOB, GPIO_PIN_3};
 LEDContext ledContextCAN1;
 LEDContext ledContextCAN2;
 
-osSemaphoreId_t xSemaphoreCAN1;
-osSemaphoreId_t xSemaphoreCAN2;
-
 osMessageQueueId_t xCAN1RxQueue;
 osMessageQueueId_t xCAN2RxQueue;
 /* USER CODE END PV */
@@ -134,14 +131,14 @@ int main(void)
     .priority = (osPriority_t) osPriorityRealtime,
   };
 
-  osThreadId_t xLEDHeartbeatCAN1;
+  osThreadId_t xLedTaskCAN1;
   const osThreadAttr_t LEDHeartbeatCAN1Attributes = {
     .name = "LED_HB_CAN1",
     .stack_size = 128 * 4,
     .priority = (osPriority_t) osPriorityVeryLow1,
   };
 
-  osThreadId_t xLEDHeartbeatCAN2;
+  osThreadId_t xLedTaskCAN2;
   const osThreadAttr_t LEDHeartbeatCAN2Attributes = {
     .name = "LED_HB_CAN2",
     .stack_size = 128 * 4,
@@ -154,15 +151,6 @@ int main(void)
   /* USER CODE END RTOS_MUTEX */
 
   /* USER CODE BEGIN RTOS_SEMAPHORES */
-  xSemaphoreCAN1 = osSemaphoreNew(32, 0, NULL);
-  xSemaphoreCAN2 = osSemaphoreNew(32, 0, NULL);
-
-  if (xSemaphoreCAN1 == NULL || xSemaphoreCAN2 == NULL) Error_Handler();
-
-  ledContextCAN1.led = &led_can1;
-  ledContextCAN1.semaphore = xSemaphoreCAN1;
-  ledContextCAN2.led = &led_can2;
-  ledContextCAN2.semaphore = xSemaphoreCAN2;
   /* USER CODE END RTOS_SEMAPHORES */
 
   /* USER CODE BEGIN RTOS_TIMERS */
@@ -179,8 +167,11 @@ int main(void)
   /* USER CODE BEGIN RTOS_THREADS */
   xCAN1rx = osThreadNew(vCANLoggerListen, &hcan1, &CAN1rxAttributes);
   xCAN2rx = osThreadNew(vCANLoggerListen, &hcan2, &CAN2rxAttributes);
-  xLEDHeartbeatCAN1 = osThreadNew(vLEDHeartbeat, &ledContextCAN1, &LEDHeartbeatCAN1Attributes);
-  xLEDHeartbeatCAN2 = osThreadNew(vLEDHeartbeat, &ledContextCAN2, &LEDHeartbeatCAN2Attributes);
+  xLedTaskCAN1 = osThreadNew(vLEDHeartbeat, &ledContextCAN1, &LEDHeartbeatCAN1Attributes);
+  xLedTaskCAN2 = osThreadNew(vLEDHeartbeat, &ledContextCAN2, &LEDHeartbeatCAN2Attributes);
+
+  ledContextCAN1.led = &led_can1;
+  ledContextCAN2.led = &led_can2;
   /* USER CODE END RTOS_THREADS */
 
   /* USER CODE BEGIN RTOS_EVENTS */
@@ -483,7 +474,6 @@ static void MX_GPIO_Init(void)
 }
 
 /* USER CODE BEGIN 4 */
-  }
 /* USER CODE END 4 */