Recognize H723

Closes #2

README.md

@@ -23,6 +23,17 @@ 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 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
+```
+
 ## Usage
 
 1. Include `can-halal.h`
@@ -31,3 +42,36 @@ 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

@@ -260,7 +260,7 @@ 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;
   }

can-halal.h

@@ -1,15 +1,36 @@
 #ifndef CAN_HALAL_H
 #define CAN_HALAL_H
 
+// 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
+    #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)