Image may be NSFW.
Clik here to view.
Image may be NSFW.
Clik here to view.
I’ve built the little NoPPP programmer. The only problem with the thing is it has no flashing lights of any kind! So I put in two LEDs, one to indicate power and the other to indicate programming voltage.
You’ll also notice that there is no PIC socket in my programmer. That’s because I am going to be doing in-circuit programming.
The NoPPP test mode was very handy in finding a couple of problems with my setup. The biggest problem was the LED I added to indicate programming voltage was draining too much current and the programming voltage dropped to about 8 volts. That was too low so I added another transistor specifically to drive the LED and all is fine.
Then I wired my PIC onto a board and tried to program it. No luck. The verify failed although chip erase seemed to work.
I tested all the voltages again with my voltmeter. Everything seemed fine. Perhaps my PIC was bad. It was brand new so that would be unlikely. I decided it was time for more analysis. I got out my dusty old rusty old CRO and had a poke around. All the data signals looked fine so I kept looking. Finally I found it, the programming voltage would drop to 6V when the chip was being programmed. This only happened for about a quarter of a second which is why I didn’t see it on my voltmeter. When the programmer was in test mode, the voltage was OK. The only difference I could spot was that in test mode, the PIC was not switched into the circuit. It sounded like my PIC might be internally shorted.
I still wasn’t ready to believe that the PIC was faulty. I checked my wiring again. Found it! There was an almost invisibly tiny solder bridge between the programming voltage pin and an I/O pin. So, once fixed, the program could be downloaded just fine.
Next I attached a LED to a random I/O pin and ran the test program that comes with NoPPP. The LED started flashing furiously. It’s a wonderful feeling when something works!
