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Bootloader and 16f877A

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sandeepa

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I am thinking of now using a bootloader for programming my 16F877A and considering the Bloader from sparkfun.com
https://www.sparkfun.com/commerce/present.php?p=PIC Boot Loader

After having a look at their tutorials, I am unclear about whether it can be used at 8MHz.do any other members have any experience with this bootloader ?

Also, I have a general bootloader question.I need to use the hardware UART of 877A for my program.However I do not need it to interface with the PC.Just the output at the Tx pin of the 877A UART at TTL levels.Will it be possible when using a bootloader since, the booltloader will also need the hardware UART and a level shifetr and all ?
I was thinking I might need something like a SPDT switch for switching between MAX232 for the bootloader and my application hardware.
Place the switch to connect Tx to MAx232 while programming the chip.Once its programmed, toggle it to connect it to the application hardware.And when new code doesnt need to be flashed, keep it in this position.Does this sound alright ?

I hope what I have said is clear.
Thnaks.
 
You'll need a programmer to load the bootloader.
Also you have to be careful your code doesn't disable the bootloader.
Here's a nice PIC bootloader site

If you're using it to program your 16F877A get a programmer instead. Cheap programmers for the 16F877A are everywhere.

Now if you want a nice programmer & debugger... ;) Talk to me.
 
I have and sue a parallel port programmer right now.But now I need to use a bootloader to be able to program the 877A in circuit.
Does anyone see any problems in using it the way i described above ?
Thnaks.
 
I can't say I'm familiar with that bootloader, but the bootloader needs to be specifically written for the clock frequency in question - most usually come with versions for 20MHz and 4MHz, for 8MHz you will probably have to alter the bootloader code?.

There should be no need to switch the RS232, simply unplug the RS232 lead from your project, and plug the PC RS232 lead in.
 
I've used the sparkfun bootloader before. The only thing I'd say is test it for a while... I had some cases where the PIC stopped working after several on/off cycles after it had been programmed with the bootloader, and it seemed that the firmware had been corrupted. I didn't look into it to see if it was the bootloader's fault, I just stopped using it to be safe.

There is no problem with using the USART pins in your application. The bootloader is a separate section of code that only runs when the PIC is first powered on, once it has finished and entered your user code you can feel free to shut off the USART module and do what you wish.

Bloader (as it is called) only comes with firmware versions for 4MHz and 20MHz for the 16F877A. It does, however, come with the C and ASM source code for each version, so it shouldn't be very hard to fix. (I believe the C compiler they use is CC5x)
 
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