PIC18F6680 programming

[rhino]

Well... if you've got tons of old ones, hack away. That's my favorite way to learn about something. Personally, I'd desolder one of the old ones and see if the code protection fuses were blown, then inspect the circuit boards to see where the differences were. If the only differences is the serial connection, then chances are the manufacturer found a bug, fixed it, then thought to themselves.... hmmm what if this happens again? So they decide to flash it with a bootloader so they can send Joe customer a new revision that he can update himself instead of sending in a board, or buying a new one, etc. Sounds like you've got nothing to lose but time and sanity! Have fun with it.

[gopher]

You may be right. I might ask the techs to unsolder the chip from the new one, they have a nice hot air rework station. I did try unsoldering one of the old ones with a soldering iron, but its to hard to get all the pins heated evenly. Thanks again.

[BobK]

Hi Gopher,

I noticed 9 holes on the front view. Alot of products in the alarm industry have either pads or holes for ICSP programming. It's possible that these holes might be for a tester or programmer. Try metering them to see if they connect to the ICSP pins on the PIC. Like you said, you've got alot of these boards. The RS232 chip could be for sending and receiving data and/or could be for a bootloader as was mentioned earlier.

HTH,

BobK

[gopher]

ok here is what i traced

max232 pins 2,5 (INVALID, FORCEON) goes to PIC pin 30 (RC0/T1OSO/T13CKI)
max232 pin 4 (T1IN TTL/CMOS Transmitter Outputs) goes to PIC oun 31 (RC6/TX/CK)
max232 pin 6 (R1OUT TTL/CMOS Receiver Outputs) goes to PIC pin 32 (RC7/RX/DT)

does this sound like it makes any sence? can USART pins be used to program a part of the chips memory ?

[skimask]

does this sound like it makes any sence? can USART pins be used to program a part of the chips memory ?

No, not without some sort of preloaded bootloader software (and the knowledge to operate it) loaded into the PIC that's already soldered on the PCB.
You need to hook into PGC/PGD/PGM/MCLR and all Vdd and Vss, and have those pins isolated from major loads on the rest of the PCB to keep from messing with the programming signals.
But you already knew that judging from Post #9...right?