Pins availables to program PIC18F452

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ZERS

New Member
Hi all,

I was wondering if the attached schematic is correct to program th e PIC18F452 'in situ'.

I've got a PIC programmer but I want to be able to re-program the PIC when it will be in position into my CD player.

The "programming" circuit is made of :
1-MAX232 to connect the DB9F cable, coming from my PC
2- The max232A is linked to the pic as follows :
- TX to RC6 (pin 26 of the PIC)
- RX to RC7 (pin 27) and RB6 (pin 39)

Is it correct ?

regards
 

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  • controller_156.jpg
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I'm presuming this is for using a 'bootloader'?, and not for using a programmer?, if so the chip needs to be programmed with the bootloader code before fitting it in the circuit.

I don't see what the connection to RB6 is for?.

Have a look at https://www.microchipc.com/PIC18bootload/ for information on bootloaders.
 
Nigel Goodwin said:
I'm presuming this is for using a 'bootloader'?, and not for using a programmer?, if so the chip needs to be programmed with the bootloader code before fitting it in the circuit.
Click to expand...
Might be that's why I'm talking about.

Let me explain :
The PIC is used to control a DIY CD PLAYER.

Firstly, the pic will be programmed using a programmer and MAPLAB "outside" the CD PLAYER.
Then the PIC will be placed in the controller board of the player.
That could be a "bootoader" but the size of the program might be big. Does a bootloader support this ?

Nigel Goodwin said:
I don't see what the connection to RB6 is for?.
Click to expand...
That's my problem. What's the good schematic ?

Regards
 

Bootloaders are usually under 256 bytes, although I've only used 16Fxxx ones.


Try the link I posted above, it tells you everything you need to know, and provides all the software.
 
thanks nigel, I've visited the link above and everything is OK, excepted the crystal frequency.

I will amend my code to deal with 20Mhz..

By the way, I did not really understand the difference (in terms of circuit) between a bootloader and a simpler programmer
Could you please explain in short terms ?


As far as the code is concerned, the application code must be located in a specific part of the memory. Adding such an instruction to the application code is not a real issue..

Regards
 
ZERS said:
By the way, I did not really understand the difference (in terms of circuit) between a bootloader and a simpler programmer
Could you please explain in short terms ?
Click to expand...

Again, that website probably explains it all!.

But basically a programmer runs software which writes to the target chip, the target chip doesn't run (and mustn't run) during this process.

A bootloader runs in the target chip, it receives a simple RS232 file from the computer, so the computer doesn't run any programming software, it's all in the target chip.

When you buy a PIC it's blank, so the only way to get code in it is to use a programmer, you can then load a bootloader into it, and use a serial port bootloader transfer after that.
 


thanks, it is clear now...

Will look into the bootloader above.

Regards
 
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