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Hello. Regarding the V3.01 bootloader.

I've implemented your bootloader on a PIC16F876.

How does the bootloader know where the downloaded programs "main" routine is? I'm a bit of a novice programmer, and I've spent the better part of the week trying to figure it out, without any avail. I've managed to get the bootloader itself working nicely, other than some comms issues with XON/XOFF flow control. However, I would like to know if and how the bootloader knows where to point PCL to the main routine of the downloaded firmware.

Thanks

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1) With reference to the above discussion, why can't a bootloader be in the first page, but above the interrupt vector, with the reset vector still jumping to the bootloader?

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I tried to explain the problem above, but perhaps it's not clear. Try again:

The problem with putting the bootloader at the start of program memory is that you will have to insert some instructions at address 0x4 to redirect the interrupt to your downloaded program. This can be done, but the problem occurs when code of your application is executing in a page other than page 0, and an interrupt occurs. When the interrupt occurs, the hardware vectors to address 0x4 - but PCLATH is still pointing to where it vectored from. The instructions needed to jump to the applications interrupt code will need to modify PCLATH. When the inerrupt vector returns, it returns elsewhere because PCLATH was changed. The next logical step is to save the state of PCLATH before jumping. This can work, but means you'll need to add code to the application's interrupt vector so that it restores PCLATH prior to the return. This can all be done, but you end up with code that has special chunks of assembly in the bootloader and the downloaded application. It also adds to the latency of the interrupt vector because of this save and jump.

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2) Are there any likely difficulties in compiling the bootloader to high memory as a function other than main, and redirecting the reset vector to it, but also calling it from the main program under the appropriate circumstance?

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That should work fine.

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Hello,

I'm trying to do bootloader of my own for PIC18F2455 and I need interrupts in bootloader and firmware.

The bootloader code is positioned at 0x0000 and firmware at 0x4000.
Before jump to firmware is made, interrupts are disabled and flag Code:

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move_int_vector

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is changed to 1.

The code I'm using for interrupt handling in bootloader is as follows:
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static vuint8 move_int_vector @ 0x0;
static vuint8 pclath_tmp1 @ 0x1;

void interrupt hi_priority_handler(void)
{
  if(!move_int_vector)
  {
    timer_isr();
  }
  else
  {
    pclath_tmp1 = PCLATH;
    GOTO(FW_INTERRUPT_VECTOR_HI);
  }
}

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Code used in firmware is as follows:
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static vuint8 move_int_vector @ 0x0;
static vuint8 pclath_tmp1 @ 0x1;

void interrupt hi_priority_handler(void)
{
   timer_isr();
    PCLATH = pclath_tmp1;
}

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However firmware crashes as soon as started, although bootloader was working normally.

The firmware works normally if no interrupts are used (I ve done some tests and bootloader correctly writes / starts firmware).

I've gone several times trough code you've provided (bootloader v2) and read the upper text regarding PCLATH...

It's been trying to do this on my own but I just can't get through

I'm not sure what I'm doing wrong here??

Best regards,

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