Use timer 1 interrupt to leave Bootloader after timeout

- remove the wait implementation 5 seconds stay in bootloader while
  loop implementation from Stanley Lio and add a timer tick counter
  to allow leaving the Bootloader once the counter reaches zero.

diff --git a/Bootloaders/DFU/BootloaderDFU.c b/Bootloaders/DFU/BootloaderDFU.c
index ce76abe..acd0296 100644 (file)
--- a/Bootloaders/DFU/BootloaderDFU.c
+++ b/Bootloaders/DFU/BootloaderDFU.c
@@ -45,8 +45,9 @@ static bool IsSecure = SECURE_MODE;
 /** Flag to indicate if the bootloader should be running, or should exit and allow the application code to run
  *  via a soft reset. When cleared, the bootloader will abort, the USB interface will shut down and the application
  *  jumped to via an indirect jump to location 0x0000 (or other location specified by the host).
+ *  Use volatile to prevent compiler to do optimization, because we change this variable from interrupt context.
  */
-static bool RunBootloader = true;
+static volatile bool RunBootloader = true;
 
 /** Flag to indicate if the bootloader is waiting to exit. When the host requests the bootloader to exit and
  *  jump to the application address it specifies, it sends two sequential commands which must be properly
@@ -55,6 +56,21 @@ static bool RunBootloader = true;
  */
 static bool WaitForExit = false;
 
+/** Minimum time in seconds stay forced into bootloader mode before application will be started. This especially
+ *  helpful if the application does not support any update or reflashing or jumping back into bootloader. It prevents
+ *  to brick the device if now ISP programmer is available.
+ */
+#ifndef BL_TIME
+#define BL_TIME 5 /* seconds */
+#endif
+
+/** Minimum time ticks stay in bootloader before application is started or negative value to prevent leaving
+ *  bootloader. Timer 1 is a 16 bit timer, which overflows after 65536 cycles if it is load with zero. The
+ *  timer 1 prescaler is programmed to divide by 64 and the prescaler engine uses a clock_div_1 divisor, means
+ *  no divisor of the CPU clock frequency F_CPU.
+ */
+static int8_t ForceBootloaderTime = ((BL_TIME) > 0) ? (F_CPU / 64 * (BL_TIME) / 65536 + 1) : -1;
+
 /** Current DFU state machine state, one of the values in the DFU_State_t enum. */
 static uint8_t DFU_State = dfuIDLE;
 
@@ -206,9 +222,6 @@ void Application_Jump_Check(void)
        }
 }
 
-
-static volatile bool stayinbootloader;
-
 /** Main program entry point. This routine configures the hardware required by the bootloader, then continuously
  *  runs the bootloader processing routine until instructed to soft-exit, or hard-reset via the watchdog to start
  *  the loaded application code.
@@ -225,29 +238,8 @@ int main(void)
        GlobalInterruptEnable();
 
        /* Run the USB management task while the bootloader is supposed to be running */
-       stayinbootloader = false;
-
-       uint16_t i = 0;
        while (RunBootloader || WaitForExit)
-       {
-               USB_USBTask();
-
-               if (!stayinbootloader)
-               {
-                       Delay_MS(1);
-                       if (i++ > 5000)
-                       {
-                               if (pgm_read_word_near(0) != 0xFFFF)
-                                       break;
-                               else
-                                       i = 0;
-                       }
-               }
-               else
-               {
-                       i = 0;
-               }
-       }
+         USB_USBTask();
 
        /* Wait a short time to end all USB transactions and then disconnect */
        _delay_us(1000);
@@ -279,6 +271,7 @@ static void SetupHardware(void)
 
        /* Bootloader active LED toggle timer initialization */
        TIMSK1 = (1 << TOIE1);
+       /* config timer 1 prescaler to F_CPU / clock_div_1 / 64 */
        TCCR1B = ((1 << CS11) | (1 << CS10));
 }
 
@@ -302,6 +295,12 @@ static void ResetHardware(void)
 ISR(TIMER1_OVF_vect, ISR_BLOCK)
 {
        LEDs_ToggleLEDs(LEDS_LED1 | LEDS_LED2);
+       /* Count number for forced ticks not below zero */
+       if (ForceBootloaderTime > 0)
+         ForceBootloaderTime--;
+       /* check if it is time to leave the bootloader and a valid application exists */
+       if ((ForceBootloaderTime == 0) && (pgm_read_word_near(0) != 0xFFFF))
+         RunBootloader = false;
 }
 
 /** Event handler for the USB_ControlRequest event. This is used to catch and process control requests sent to
@@ -317,7 +316,8 @@ void EVENT_USB_Device_ControlRequest(void)
                return;
        }
 
-stayinbootloader = true;
+       /* prevent counter to reach zero */
+       ForceBootloaderTime = -1;
 
        /* Activity - toggle indicator LEDs */
        LEDs_ToggleLEDs(LEDS_LED1 | LEDS_LED2);