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Tait's (7407-PNP) programmer w/PIC16F628A

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Joel Rainville

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Finally! It works! No more irritating "program verify failed at address 0x000"!

5 days ago, I knew absolutely nothing about microcontrollers. I build electric guitars as a hobby, and I was browsing the net to read about some guitar parts building machinery, and stumbled upon someone's site saying he programmed a trusty 16F628 to act as a counter/controller for his machine.

I was intrigued. I remembered a bit of electronics theory back from high school (mostly resistors' color code :lol:) and thought : why not?!

Found Microchip's web site and quickly ordered a 16F628A sample - along with a 16F684 for some reason.

I spent the last 3 days (and the *whole* 3 days, from 7am to 3am, or the other way around, I'm not exactly sure) reading about PICs, looking at datasheets, studying David Tait's schematics, soldering, desoldering, taking a trip to the local electronics surplus store to get a breadboard, trying *all* the compatible software (WinPic, WinPicProg, Propic 2 and XP, IC-Prog, FPP, etc.)

Nothing worked.

I was about to call it quits when I found numerous posts on this forum by Nigel that explained how to use the Hardware options menu in his software to check for voltage levels on the PIC's pins.

13.3V on MCLR. Check. VDD's fine. RB7 too. RB6... Nothing's happening on RB6! Looking at the schematics, I realize there is not a lot of possibilities here. Resistor busted (or wrong value)? Nope. Wrong or no connection to the DB25 cable/connector? No. This only leaves the 7407 at fault.

Crap. It's sunday night, everything's closed, so I can't get a 7407 replacement until probably a couple of days. Might as well go to bed...

My sleep deprived mind almost to sleep, I had a flash :

- Wait a minute, if voltages are fine everywhere else, this probably means that only one gate on the 7407 is busted. I probably shorted/destroyed it during my first attempts at soldering everything to a prototype board.

Could I use the unused gate (pins 12-13) on the 7407 instead? Would it still be functional?

You bet.

All the programming software works now - but Nigel's WinPicProg's definitely the coolest ;) I have a working 7407-PNP programmer with a cool green flashing led *and* a programmed 16F628A :lol:

Moral of the story : don't give up... and hold back posting about the dreaded "program verify failed at address 0x000" until you've gone through every possible possibility, which for a beginner should apparently represent around 3 days worth of reading/browsing/trying/not eating :lol:

Sorry for the length of this post, but I figured that if I started with "program verify failed at address 0x000" in the first sentence, pros would get scared away pretty fast, and only beginners like me would be left and they could maybe learn from my experience. (I also used a lot of keywords on purpose so that my post will show up in searches on programmer problems)

Thanks for reading!
 
I always like to see that somebody made his way to PICs. The hardest thing is to start, now when you made it through all your trouble, you can do almost anything!

Have fun :D
 
great !!!

actually i have a simillar story. i didnt order a pre-made kit in which you only have to do the soldering. i made my P16PRO programmer myself. and yes i had alot of problems with it. but in the end im happy with it. its so simple and its so cheap :D
 
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