Fix for occasional timeout on writes...

...Downstream was not always changing state correctly after closely
spaced interrupts.

Also improve flash-write-lockout function to avoid dependency on
optimisation level.

Downstream/Src/interrupts.c

@@ -46,6 +46,8 @@ extern HCD_HandleTypeDef hhcd_USB_OTG_FS;
 extern DMA_HandleTypeDef hdma_spi1_rx;
 extern DMA_HandleTypeDef hdma_spi1_tx;
 
+extern volatile uint8_t UsbInterruptHasHappened;
+
 uint8_t BusFaultAllowed = 0;
 
 
@@ -83,9 +85,8 @@ void DMA2_Stream3_IRQHandler(void)
 
 void OTG_FS_IRQHandler(void)
 {
-    //INT_ACTIVE_ON;
     HAL_HCD_IRQHandler(&hhcd_USB_OTG_FS);
-    //INT_ACTIVE_OFF;
+    UsbInterruptHasHappened = 1;
 }
 
 
@@ -93,6 +94,11 @@ void OTG_FS_IRQHandler(void)
 //The deliberate flash lockout will cause a bus fault that we need to process.
 void EnableOneBusFault(void)
 {
+    //It should not be enabled already!
+    if (BusFaultAllowed)
+    {
+        while (1);
+    }
     SCB->SHCSR = SCB_SHCSR_BUSFAULTENA_Msk;
     BusFaultAllowed = 1;
 }

Downstream/Src/main.c

@@ -44,16 +44,17 @@
 
 
 /* Private function prototypes -----------------------------------------------*/
-void SystemClock_Config(void);
+static void SystemClock_Config(void);
 static void GPIO_Init(void);
-void DisableFlashWrites(void);
-void CheckFirmwareMatchesHardware(void);
+static void DisableFlashWrites(void);
+static void CheckFirmwareMatchesHardware(void);
+
+volatile uint8_t    UsbInterruptHasHappened = 0;
+uint8_t             IterationCount = 0;
 
 
 int main(void)
 {
-    uint32_t iterationCount = 0;
-
     //First things first!
     DisableFlashWrites();
     CheckFirmwareMatchesHardware();
@@ -77,12 +78,17 @@ int main(void)
         Downstream_SPIProcess();
         Downstream_PacketProcessor_CheckNotifyDisconnectReply();
 
+        //Count number of main loops since last USB interrupt
+        if (UsbInterruptHasHappened)
+        {
+            UsbInterruptHasHappened = 0;
+            IterationCount = 0;
+        }
+
         //Some USB host state transitions take 3 iterations to fully apply.
         //We'll be generous and give it 5 before sleeping.
-        iterationCount++;
-        if (iterationCount > 4)
+        if (IterationCount++ > 4)
         {
-            iterationCount = 0;
             __WFI();                //sleep time!
         }
     }
@@ -97,10 +103,11 @@ void DisableFlashWrites(void)
     FLASH->KEYR = 999;
 
     //Confirm that flash cannot be unlocked
-    //This unlock attempt will also cause a bus fault.
-    EnableOneBusFault();
+    //This unlock attempt will also cause two bus faults.
     if ((FLASH->CR & FLASH_CR_LOCK) == 0) while(1);
+    EnableOneBusFault();
     FLASH->KEYR = FLASH_KEY1;
+    EnableOneBusFault();
     FLASH->KEYR = FLASH_KEY2;
     if ((FLASH->CR & FLASH_CR_LOCK) == 0) while(1);
 }

Upstream/Src/interrupts.c

@@ -76,16 +76,12 @@ void OTG_FS_IRQHandler(void)
 
 void DMA2_Stream2_IRQHandler(void)
 {
-//    INT_ACTIVE_ON;
     HAL_DMA_IRQHandler(&spiRxDmaHandle);
-//    INT_ACTIVE_OFF;
 }
 
 void DMA2_Stream3_IRQHandler(void)
 {
-//    INT_ACTIVE_ON;
     HAL_DMA_IRQHandler(&spiTxDmaHandle);
-//    INT_ACTIVE_OFF;
 }
 
 void EXTI3_IRQHandler(void)
@@ -101,6 +97,11 @@ void EXTI3_IRQHandler(void)
 //The deliberate flash lockout will cause a bus fault that we need to process.
 void EnableOneBusFault(void)
 {
+    //It should not be enabled already!
+    if (BusFaultAllowed)
+    {
+        while (1);
+    }
     SCB->SHCSR = SCB_SHCSR_BUSFAULTENA_Msk;
     BusFaultAllowed = 1;
 }

Upstream/Src/main.c

@@ -44,15 +44,11 @@
 #include "interrupts.h"
 
 
-/* Private variables ---------------------------------------------------------*/
-
-
-
 /* Private function prototypes -----------------------------------------------*/
-void SystemClock_Config(void);
-void GPIO_Init(void);
-void DisableFlashWrites(void);
-void CheckFirmwareMatchesHardware(void);
+static void SystemClock_Config(void);
+static void GPIO_Init(void);
+static void DisableFlashWrites(void);
+static void CheckFirmwareMatchesHardware(void);
 
 
 
@@ -92,10 +88,11 @@ void DisableFlashWrites(void)
     FLASH->KEYR = 999;
 
     //Confirm that flash cannot be unlocked
-    //This unlock attempt will also cause a bus fault.
-    EnableOneBusFault();
+    //This unlock attempt will also cause two bus faults.
     if ((FLASH->CR & FLASH_CR_LOCK) == 0) while(1);
+    EnableOneBusFault();
     FLASH->KEYR = FLASH_KEY1;
+    EnableOneBusFault();
     FLASH->KEYR = FLASH_KEY2;
     if ((FLASH->CR & FLASH_CR_LOCK) == 0) while(1);
 }