Merge pull request ARMmbed#15472 from jtmyz9/jmcloud/STM32-use-more-t…

…han-one-fifo

Don't overlap STM32 FDCAN RAM sections

targets/TARGET_STM/can_api.c

@@ -183,8 +183,11 @@ static void _can_init_freq_direct(can_t *obj, const can_pinmap_t *pinmap, int hz
     obj->CanHandle.Init.DataTimeSeg1 = 0x1;        // Not used - only in FDCAN
     obj->CanHandle.Init.DataTimeSeg2 = 0x1;        // Not used - only in FDCAN
 #ifdef TARGET_STM32H7
-    /* Message RAM offset is only supported in STM32H7 platforms of supported FDCAN platforms */
-    obj->CanHandle.Init.MessageRAMOffset = 0;
+    /* Message RAM offset is only supported in STM32H7 platforms of supported FDCAN platforms 
+    * Total RAM size is 2560 words, each FDCAN object allocates approx 300 words, so offset each by 
+    * 512 to make sure RAM sections don't overlap if using multiple FDCAN instances on one chip
+    */
+    obj->CanHandle.Init.MessageRAMOffset = obj->index * 512;
 
     /* The number of Standard and Extended ID filters are initialized to the maximum possile extent
      * for STM32H7 platforms
@@ -1222,7 +1225,6 @@ static void can_irq(CANName name, int id)
         // rx interrupts will be unamsked in read operation. reads must be deffered to thread context.
         // refer to the CAN receive interrupt problem due to mutex and resolution section of README doc.
         __HAL_CAN_DISABLE_IT(&CanHandle, CAN_IT_FMP0);
-
         irq_handler(can_irq_contexts[id], IRQ_RX);
     }