/******************************************************************************
* Function: void main(void)
*
* PreCondition: None
*
* Input: None
*
* Output: None
*
* Side Effects: None
*
* Overview: This is the first code that executes during boot up of
* the microcontroller. This code checks to see if execution
* should stay in the "bootloader" mode, or if it should jump
* into the "application" (non-bootloder) execution mode.
* No other unrelated code should be added to this function.
*
* Note: THIS FUNCTION EXECUTES PRIOR TO INITIALIZATION OF THE C
* STACK. NO C INITIALIZATION OF STATIC VARIABLES OR RESOURCES
* WILL OCCUR, PRIOR TO EXECUTING THIS FUNCTION. THEREFORE,
* THE CODE IN THIS FUNCTION MUST NOT CALL OTHER FUNCTIONS OR
* PERFORM ANY OPERATIONS THAT WILL REQUIRE C INITIALIZED
* BEHAVIOR.
*****************************************************************************/
void main(void)
{
//Assuming the I/O pin check entry method is enabled, check the I/O pin value
//to see if we should stay in bootloader mode, or jump to normal applicaiton
//execution mode.
#ifdef ENABLE_IO_PIN_CHECK_BOOTLOADER_ENTRY
//Need to make sure the I/O pin is configured for digital mode so we
//can sense the digital level on the input pin.
mInitSwitch2();
//Check Bootload Mode Entry Condition from the I/O pin (ex: place a
//pushbutton and pull up resistor on the pin)
if(sw2 == 1)
{
//If we get to here, the user is not pressing the pushbutton. We
//should default to jumping into application run mode in this case.
//Restore default "reset" value of registers we may have modified temporarily.
mDeInitSwitch2();
//Before going to application image however, make sure the image
//is properly signed and is intact.
goto DoFlashSignatureCheck;
}
else
{
//User is pressing the pushbutton. We should stay in bootloader mode
BootMain();
}
#endif //#ifdef ENABLE_IO_PIN_CHECK_BOOTLOADER_ENTRY
DoFlashSignatureCheck:
//Check if the application region flash signature is valid
if(*(ROM unsigned int*)APP_SIGNATURE_ADDRESS == APP_SIGNATURE_VALUE)
{
//The flash signature was valid, implying the previous
//erase/program/verify operation was a success.
//Also make sure the first WORD of program memory in the app space
//is not blank, meaning there is an application image programmed into the device.
if(*(ROM unsigned int*)REMAPPED_APPLICATION_RESET_VECTOR != 0xFFFF)
{
//Go ahead and jump out of bootloader mode into the application run mode
#ifdef __XC8__
#asm
goto REMAPPED_APPLICATION_RESET_VECTOR
#endasm
#else //Must be C18 instead
_asm goto REMAPPED_APPLICATION_RESET_VECTOR _endasm
#endif
}
}
//else the application image is missing or corrupt. In this case, we
//need to stay in the bootloader mode, so the user has the ability to
//try (again) to re-program a valid application image into the device.
//We should stay in bootloader mode
BootMain();
}//end UninitializedMain
/******************************************************************************
* Function: void UninitializedMain(void)
*
* PreCondition: None
*
* Input: None
*
* Output: None
*
* Side Effects: None
*
* Overview: This is the first code that executes during boot up of
* the microcontroller. This code checks to see if execution
* should stay in the "bootloader" mode, or if it should jump
* into the "application" (non-bootloder) execution mode.
* No other unrelated code should be added to this function.
*
* Note: THIS FUNCTION EXECUTES PRIOR TO INITIALIZATION OF THE C
* STACK. NO C INITIALIZATION OF STATIC VARIABLES OR RESOURCES
* WILL OCCUR, PRIOR TO EXECUTING THIS FUNCTION. THEREFORE,
* THE CODE IN THIS FUNCTION MUST NOT CALL OTHER FUNCTIONS OR
* PERFORM ANY OPERATIONS THAT WILL REQUIRE C INITIALIZED
* BEHAVIOR.
*****************************************************************************/
void UninitializedMain(void)
{
//Assuming the I/O pin check entry method is enabled, check the I/O pin value
//to see if we should stay in bootloader mode, or jump to normal applicaiton
//execution mode.
#ifdef ENABLE_IO_PIN_CHECK_BOOTLOADER_ENTRY
//Need to make sure the I/O pin is configured for digital mode so we
//can sense the digital level on the input pin.
mInitSwitch2();
//Check Bootload Mode Entry Condition from the I/O pin (ex: place a
//pushbutton and pull up resistor on the pin)
if(sw2 == 1)
{
//If we get to here, the user is not pressing the pushbutton. We
//should default to jumping into application run mode in this case.
//Restore default "reset" value of registers we may have modified temporarily.
mDeInitSwitch2();
//Before going to application image however, make sure the image
//is properly signed and is intact.
goto DoFlashSignatureCheck;
}
else
{
//User is pressing the pushbutton. We should stay in bootloader mode
_asm goto BootMain _endasm
}
#endif //#ifdef ENABLE_IO_PIN_CHECK_BOOTLOADER_ENTRY
DoFlashSignatureCheck:
//Check if the application region flash signature is valid
#ifdef ENABLE_FLASH_SIGNATURE_VERIFICATION
if(*(rom unsigned int*)APP_SIGNATURE_ADDRESS == APP_SIGNATURE_VALUE)
{
//The flash signature was valid, implying the previous
//erase/program/verify operation was a success.
//Go ahead and jump out of bootloader mode into the application run mode
_asm goto REMAPPED_APPLICATION_RESET_VECTOR _endasm
}
/******************************************************************************
* Function: void main(void)
*
* PreCondition: None
*
* Input: None
*
* Output: None
*
* Side Effects: None
*
* Overview: This is the first code that executes during boot up of
* the microcontroller. This code checks to see if execution
* should stay in the "bootloader" mode, or if it should jump
* into the "application" (non-bootloder) execution mode.
* No other unrelated code should be added to this function.
*
* Note:
*****************************************************************************/
void main(void)
{
unsigned int i;
//Note: If you disable MLCR (so it gets used as RA3 general purpose input)
//and then use RA3 as the bootloader entry check I/O pin, it is recommended
//to have some bootup delay prior to checking the RA3 pin to see if entry
//into the bootloader or application should occur. This is useful if there
//is capacitance on RA3 and the pull up is weak enought that the RA3 rises
//slower than VDD. Without a bootup delay here, this could allow the
//microcontroller to execute and check the I/O pin when it has not yet reached
//the proper value. This is also possible immediately after exiting ICSP programming
//mode, as it may take some time for the programmer to tri-state the MCLR/RA3
//pin and for the pull up resistor to overcome any capacitance on the pin.
for(i = 0; i < 1000; i++); //Make sure this delay is long enough for the sw2 pin can
//fully settle to the correct value based on the PCB circuit,
//prior to doing the I/O pin bootloader entry check.
//Perform startup check of I/O pin to see if we should stay in bootloader
//mode (ex: because the user is pressing the pushbutton on the board)
#if defined(ENABLE_IO_PIN_CHECK_BOOTLOADER_ENTRY) //See usb_config.h
mInitSwitch2();
if(sw2 == 0)
{
//Statup check of I/O pin detected low state. Stay in bootloader mode.
BootMain();
}
#endif
//If we get to here, that means the user is not trying to enter bootloader
//mode by I/O pin. However, we still need to stay in bootloader mode
//if no application firmware image is present at all, or if the last
//erase/program/verify sequence was interrupted, causing the flash memory
//signature word location to contain the wrong value.
//Check to verify the flash memory has the correct signature word
//value, indicating that the application space firmware image is intact
//and was successfully erased/programmed/verified/signed when last
//reprogrammed.
PMCON1bits.CFGS = 0;
PMADR = APP_SIGNATURE_ADDRESS;
PMCON1bits.RD = 1; //Initiate flash memory read operation
Nop(); //2 Nops() required, see datasheet
Nop();
if((PMDATL == APP_SIGNATURE_VALUE) && (PMDATH == RETLW_OPCODE_MSB))
{
//The signature word was valid. Now make one more check to ensure
//0x900 has been programmed with a non blank value (ex: != 0x3FFF),
//indicating that an application firmware image has been programmed
//into the device.
PMADR = APP_SPACE_RESET_VECTOR;
PMCON1bits.RD = 1; //Initiate flash memory read operation
Nop(); //2 Nops() required, see datasheet
Nop();
//Check for completely blank value or not. If the location is not
//blank, this means we have an application firmware image programmed
//in the device, and we should jump to it now.
if(PMDAT != BLANK_FLASH_WORD_VALUE)
{
//Jump out of this bootloader firmware and into the main
//application firmware entry point at APP_SPACE_START_ADDRESS.
#asm
movlp APP_SPACE_START_HI_BYTE
goto APP_SPACE_START_LOWER_11BITS
#endasm
}
