fix buffer index calculation

they take a bit field as an argument, and then immediately use a clz instruction to convert it back to an index for some reason

README.md

@@ -18,11 +18,26 @@ is included:
 
 - `STM32F3`
 - `STM32H7`
+- `STM32F0`
 
 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.:
+
+```yaml
+# Compiler definitions. The -D prefix for the compiler will be automatically added.
+cDefinitions:
+  - STM32H7
+  - FTCAN_NUM_FILTERS=32
+  - FTCAN_NUM_TX_BUFFERS=10 # optional, only if using dedicated tx buffers
+```
+
 ## Usage
 
 1. Include `can-halal.h`
@@ -31,3 +46,36 @@ in your `.ioc`).
 4. To transmit messages, call `ftcan_transmit()`
 5. When a message is received, `ftcan_msg_received_cb()` is called. It has a
    default empty implementation, which you can simply override.
+
+## Enabling CAN in STM32CubeMX
+
+This isn't specific to `can-halal`, but for completeness sake is included here.
+
+### bxCAN (e.g. STM32F3xx)
+
+1. Enable the CAN peripheral  
+   ![Connectivity -> CAN -> Activated](doc/bxcan-activate.png)
+2. Setup the [bit timings](http://bittiming.can-wiki.info/).  
+   **Note:** the baud rate depends on your system clock, so make sure that is
+   setup correctly first!  
+   ![Connectivity -> CAN -> Parameter Settings -> Bit Timings Parameters](doc/bxcan-bittimings.png)
+3. Make sure the CAN_RX0 interrupt is enabled  
+   ![Connectivity -> CAN -> NVIC Settings -> CAN_RX0 interrupt](doc/bxcan-interrupt.png)
+
+### FDCAN (e.g. STM32H7xx)
+
+1. Enable the CAN peripheral  
+   ![Connectivity -> FDCAN(1)](doc/fdcan-activate.png)
+2. Setup the frame format, nominal SJW, filters, and FIFOs. The numbers for
+   filters/FIFOs in the screenshot are examples.  
+   **Note:** You need to tell `can-halal` about the number of filters by
+   defining `FTCAN_NUM_FILTERS` (see above).  
+   ![Connectivity -> FDCAN(1) -> Parameter Settings -> Basic Parameters](doc/fdcan-basic.png)
+3. Setup the [bit timings](http://bittiming.can-wiki.info/). We only use CAN in
+   classic mode, not FD mode, so we only need to worry about the nominal bit
+   timings  
+   **Note:** the baud rate depends on your system clock, so make sure that is
+   setup correctly first!  
+   ![Connectivity -> FDCAN(1) -> Parameter Settings -> Bit Timings Parameters](doc/fdcan-bittimings.png)
+4. Make sure the interrupts are enabled
+   ![Connectivity -> FDCAN(1) -> NVIC Settings](doc/fdcan-interrupt.png)

can-halal.c

@@ -100,51 +100,51 @@ HAL_StatusTypeDef ftcan_init(FDCAN_HandleTypeDef *handle) {
   return HAL_FDCAN_Start(hcan);
 }
 
-HAL_StatusTypeDef ftcan_transmit(uint16_t id, const uint8_t *data,
-                                 size_t datalen) {
-  static FDCAN_TxHeaderTypeDef header;
-  header.Identifier = id;
-  header.IdType = FDCAN_STANDARD_ID;
-  header.TxFrameType = FDCAN_DATA_FRAME;
+static FDCAN_TxHeaderTypeDef * fdcan_initialize_tx_header(FDCAN_TxHeaderTypeDef * header, uint16_t id, size_t datalen) {
+  header->Identifier = id;
+  header->IdType = FDCAN_STANDARD_ID;
+  header->TxFrameType = FDCAN_DATA_FRAME;
   switch (datalen) {
   case 0:
-    header.DataLength = FDCAN_DLC_BYTES_0;
+    header->DataLength = FDCAN_DLC_BYTES_0;
     break;
   case 1:
-    header.DataLength = FDCAN_DLC_BYTES_1;
+    header->DataLength = FDCAN_DLC_BYTES_1;
     break;
   case 2:
-    header.DataLength = FDCAN_DLC_BYTES_2;
+    header->DataLength = FDCAN_DLC_BYTES_2;
     break;
   case 3:
-    header.DataLength = FDCAN_DLC_BYTES_3;
+    header->DataLength = FDCAN_DLC_BYTES_3;
     break;
   case 4:
-    header.DataLength = FDCAN_DLC_BYTES_4;
+    header->DataLength = FDCAN_DLC_BYTES_4;
     break;
   case 5:
-    header.DataLength = FDCAN_DLC_BYTES_5;
+    header->DataLength = FDCAN_DLC_BYTES_5;
     break;
   case 6:
-    header.DataLength = FDCAN_DLC_BYTES_6;
+    header->DataLength = FDCAN_DLC_BYTES_6;
     break;
   case 7:
-    header.DataLength = FDCAN_DLC_BYTES_7;
+    header->DataLength = FDCAN_DLC_BYTES_7;
     break;
   case 8:
   default:
-    header.DataLength = FDCAN_DLC_BYTES_8;
+    header->DataLength = FDCAN_DLC_BYTES_8;
     break;
   }
-  header.ErrorStateIndicator = FDCAN_ESI_PASSIVE;
-  header.BitRateSwitch = FDCAN_BRS_OFF;
-  header.FDFormat = FDCAN_CLASSIC_CAN;
-  header.TxEventFifoControl = FDCAN_NO_TX_EVENTS;
+  header->ErrorStateIndicator = FDCAN_ESI_PASSIVE;
+  header->BitRateSwitch = FDCAN_BRS_OFF;
+  header->FDFormat = FDCAN_CLASSIC_CAN;
+  header->TxEventFifoControl = FDCAN_NO_TX_EVENTS;
 
-  // HAL_FDCAN_AddMessageToTxFifoQ doesn't modify the data, but it's not marked
-  // as const for some reason.
-  uint8_t *data_nonconst = (uint8_t *)data;
-  return HAL_FDCAN_AddMessageToTxFifoQ(hcan, &header, data_nonconst);
+  return header;
+}
+
+HAL_StatusTypeDef ftcan_transmit(uint16_t id, const uint8_t *data, size_t datalen) {
+    static FDCAN_TxHeaderTypeDef header;
+    return HAL_FDCAN_AddMessageToTxFifoQ(hcan, fdcan_initialize_tx_header(&header, id, datalen), data);
 }
 
 HAL_StatusTypeDef ftcan_add_filter(uint16_t id, uint16_t mask) {
@@ -220,10 +220,34 @@ void HAL_FDCAN_RxFifo0Callback(FDCAN_HandleTypeDef *handle,
 
   ftcan_msg_received_cb(header.Identifier, datalen, data);
 }
+
+HAL_StatusTypeDef ftcan_get_tx_queue_length(uint32_t *length) {
+  if (length == NULL) {
+    return HAL_ERROR;
+  }
+  *length = HAL_FDCAN_GetTxFifoFreeLevel(hcan);
+  return HAL_OK;
+}
+
+#if FTCAN_NUM_TX_BUFFERS
+static_assert(FDCAN_TX_BUFFER11 == 1 << 11 && FDCAN_TX_BUFFER21 == 1 << 21, "Your HAL version has a different definition for the transmit buffer indices. Please update your HAL version or change the code below.");
+
+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, 1 << buffer_index);
+}
+#endif // FTCAN_NUM_TX_BUFFERS
 #endif
 
 __weak void ftcan_msg_received_cb(uint16_t id, size_t datalen,
-                                  const uint8_t *data) {}
+                            const uint8_t *data) {
+  (void)id;
+  (void)datalen;
+  (void)data;
+}
 
 uint64_t ftcan_unmarshal_unsigned(const uint8_t **data_ptr, size_t num_bytes) {
   if (num_bytes > 8) {
@@ -260,7 +284,7 @@ uint8_t *ftcan_marshal_unsigned(uint8_t *data, uint64_t val, size_t num_bytes) {
     num_bytes = 8;
   }
 
-  for (size_t i = num_bytes - 1; i >= 0; i++) {
+  for (int i = num_bytes - 1; i >= 0; i--) {
     data[i] = val & 0xFF;
     val >>= 8;
   }
@@ -270,4 +294,4 @@ uint8_t *ftcan_marshal_unsigned(uint8_t *data, uint64_t val, size_t num_bytes) {
 
 uint8_t *ftcan_marshal_signed(uint8_t *data, int64_t val, size_t num_bytes) {
   return ftcan_marshal_unsigned(data, val, num_bytes);
-}
+}

can-halal.h

@@ -1,15 +1,36 @@
 #ifndef CAN_HALAL_H
 #define CAN_HALAL_H
 
-#if defined(STM32F302x8) || defined(STM32F302xB)  || defined(STM32F302xC) || defined(STM32F3)
-#include "stm32f3xx_hal.h"
-#define FTCAN_IS_BXCAN
-#define FTCAN_NUM_FILTERS 13
+// Define family macros if none are defined and we recognize a chip macro
+#if !defined(STM32F3) && !defined(STM32H7) && !defined(STM32F0)
+#if defined(STM32F302x6) || defined(STM32F302x8) || defined(STM32F302xB) ||    \
+    defined(STM32F302xC)
+#define STM32F3
+#endif
+#if defined(STM32H7A3xx) || defined(STM32H723xx)
+#define STM32H7
+#endif
+#if defined(STM32F042x6)
+#define STM32F0
+#endif
+#endif
+
+#if defined(STM32F3)
+    #include "stm32f3xx_hal.h"
+    #define FTCAN_IS_BXCAN
+    #define FTCAN_NUM_FILTERS 13
 #elif defined(STM32H7)
-#include "stm32h7xx_hal.h"
-#define FTCAN_IS_FDCAN
+    #include "stm32h7xx_hal.h"
+    #define FTCAN_IS_FDCAN
+    #ifndef FTCAN_NUM_FILTERS
+        #error "Please configure the number of filters in CubeMX, and then add a compiler define for FTCAN_NUM_FILTERS"
+    #endif
+#elif defined(STM32F0)
+    #include "stm32f0xx_hal.h"
+    #define FTCAN_IS_BXCAN
+    #define FTCAN_NUM_FILTERS 13
 #else
-#error "Couldn't detect STM family"
+    #error "Couldn't detect STM family"
 #endif
 
 #if defined(FTCAN_IS_BXCAN)
@@ -20,6 +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);