Hi Folks,
I am back with a bit more on this topic. Using the information at Jaromir Sukuba's website as well as info from the downloadable source files for QwikBug which were generated more than a decade ago, I did make my own in-circuit debugger for the PIC182550 which could no doubt be easily ported to other PIC18 chips. This debugger, called
DBg, can be made to work with assembly language programs downloaded via a Microchip USB bootloader. However, currently it is not the most straightforward thing to set up. I should think it could be used with compiled programs as well but that is outside my area of knowledge with the PIC processors.
By keeping all the code that does anything in the debugger itself, I managed to make it work with very inexpensive hardware and only a terminal emulator in the PC which is where one directs the debug operation. The debugger requires about 734 (decimal) bytes of Flash.
If anyone is interested, a web page describing this can be found at
http://www.angelfire.com/oh3/ebjoew/DBg.htmlThe web page endeavors to not only present the debugger but also tries to lay down a little more cleanly the known details about the undocumented Debug mode hardware in the PIC18 chips.
For those who are concerned about such things, that web page is not intended to show newbies the optimum way or the "right" way to write PIC programs. It is just how I wrote this one. Well, that is sort of true. I actually have my own set of mnemonics that I use when I write PIC code. If I care to publish my code on the internet for others, I translate it to the standard Microchip mnemonics.
Also, yes, I am fully aware that there is a good in-circuit debugging facility available from Microchip that is nicely integrated into their development system. I just like to keep things simple and where I have access to everything that is going on. If something does not work, I don't have to work around the problem while somebody far away eventually gets around to fixing it.