add include guards, update readme

README.md

@@ -24,6 +24,8 @@ When using the FDCAN peripheral (H7 series), you also need to define
 `FTCAN_NUM_FILTERS` (and set it to the value of "Std Filters Nbr" you configured
 in your `.ioc`).
 
+If you want to use the dedicated buffers of the FDCAN, you must additionally define `FTCAN_NUM_TX_BUFFERS` (set to value of "Tx Buffers Nbr" in CubeMX).
+
 If you use
 [VSCode with the stm-32-for-vscode extension](https://podio.com/fasttubede/modulubergreifend/apps/tech-tutorials/items/57),
 you can add these definitions in the `STM32-for-VSCode-config.yaml` file, e.g.:
@@ -33,6 +35,7 @@ you can add these definitions in the `STM32-for-VSCode-config.yaml` file, e.g.:
 cDefinitions:
   - STM32H7
   - FTCAN_NUM_FILTERS=32
+  - FTCAN_NUM_TX_BUFFERS=10 # optional, only if using dedicated tx buffers
 ```
 
 ## Usage

can-halal.c

@@ -229,10 +229,15 @@ HAL_StatusTypeDef ftcan_get_tx_queue_length(uint32_t *length) {
   return HAL_OK;
 }
 
+#if FTCAN_NUM_TX_BUFFERS
 HAL_StatusTypeDef ftcan_transmit_buffer(uint16_t id, const uint8_t *data, size_t datalen, uint32_t buffer_index) {
     static FDCAN_TxHeaderTypeDef header;
+    if (buffer_index >= FTCAN_NUM_TX_BUFFERS) {
+        return HAL_ERROR;
+    }
     return HAL_FDCAN_AddMessageToTxBuffer(hcan, fdcan_initialize_tx_header(&header, id, datalen), data, buffer_index);
 }
+#endif // FTCAN_NUM_TX_BUFFERS
 #endif
 
 __weak void ftcan_msg_received_cb(uint16_t id, size_t datalen,

can-halal.h

@@ -41,6 +41,13 @@ HAL_StatusTypeDef ftcan_init(FDCAN_HandleTypeDef *handle);
 #error "Unknown CAN peripheral"
 #endif
 
+#if defined(FTCAN_IS_FDCAN) && defined(FTCAN_NUM_TX_BUFFERS)
+static_assert(FTCAN_NUM_TX_BUFFERS > 0,
+               "If you want to use the dedicated transmit buffers, you must define FTCAN_NUM_TX_BUFFERS as configured in CubeMX (at least 1).");
+
+HAL_StatusTypeDef ftcan_transmit_buffer(uint16_t id, const uint8_t *data, size_t datalen, uint32_t buffer_index);
+#endif // FTCAN_IS_FDCAN && FTCAN_NUM_TX_BUFFERS
+
 HAL_StatusTypeDef ftcan_transmit(uint16_t id, const uint8_t *data,
                                  size_t datalen);