Boot loader problems with a 18F4550

Jon Chandler · Post by **Jon Chandler** » Tue Sep 09, 2008 3:01 pm

I'm having a problem once in a while using the boot loader with an 18F4550.

The boot loader with work fine for anywhere between a handful of load cycles and a hundred or more but once in a while it hangs up during the load process. This might be WinXP delaying the data transfer but I'm not sure. Most of the time (but not every time), if the process hangs, I can't program the chip again. If I re-start the boot loader, it won't recognize a reset button push and nothing will happen.

My conclusion is that somehow the boot loader code got nailed when the data transfer got interrupted. So the next step is to reload the boot loader code. I use the Olimex USB PicStart+ clone sold by SparkFun. Reloading results in a bunch of reported errors in the configuration bits. The chip seems to go through the process. Of course, with the configuration bit errors the boot loader still won't work and the chip is functionally dead.

Note that this is the same programmer I used to install the boot loader code in the first place and everything works great until the boot load process stops in the middle of a cycle. My board uses a MAX232 chip on the serial interface, has bypass caps at each pair of power pins on the PIC and has a 10k pullup on /MCLR.

Has anybody else had this problem? Any idea how to prevent it or how to recover the growing pile of dead chips?

Thanks,

Jon

liak · Post by **liak** » Wed Sep 10, 2008 3:59 pm

Dear Jon,
I used bootloader on the same PIC once. I also used it on others like 18F1320 and 18F2525. Very convenient. I am replying to say that I had similar experience like you.
It happens after a few hundred cycles of programming the PIC. I noticed it happens when the WinXP hanged in the middle of data transfer. After that the PIC will not work again. I am not sure why it happens. But somehow the bootloader gets damaged in the process.
Fortunately for me, sofar I have never had a failed PIC in the process. The PIC will run like normal again after I re-program the bootloader in it. I use Galep32 programmer.

Regards,
Liak

Jon Chandler · Post by **Jon Chandler** » Fri Sep 12, 2008 3:40 pm

The problem is solved. I used a friend's PICKit 2 programmer to erase and reload the boot loader into 3 parts. Two of them work fine and the 3rd actually has a bad memory location reported by the PICKit software.

For some reason, my Olimex PICStart+ clone can't erase the chips. It's always been a pain to use, usually requiring uninstalling drivers and reboot the PC several times to make it work.

The PICKit 2 is really nice. One is on order today!

Jon