I'm at a loss

[Acetronics2]

Hello,

OK, can't seem to figure this one out. I have a PIC16F628A that I have written code for. I try to program it and I get this, "Target Device does not match selected device". Now, the funny part is this...I have the microcontroller device ID entered correctly, as well as the ICSP pins connected correctly.

When I've made a mistake in the past on other chips and clicked program, the above message occurred immediately. What's happening now is the status bar runs about 3 times and then I get the message. It looks like it's going to program, but then it fails. Any thoughts? It's not my programmer because it'll program other chips, but as soon as I try to program the 628A, it fails after 3 status bar sweeps. Thoughts?

I always get such a message when I forget to enable power to the target with my PK2 or 3 ...

moreover, the Pickit current capacity is limited ... sooo, couldn't your board draw too much current ??? ( as you talk about ICSP ...)

and in the end, I remember a Microchip errata sheet about this subject for some series of those programmers ...

Alain

[AvionicsMaster1]

I'm not familiar with the Pickit but I have gotten a similar message when I haven't properly isolated the programming pins. I usually put a switch in the circuit to disconnect the rest of the circuit. If you look in the manual it recommends some minimum values when connecting your circuit.

[ERMEGM]

Thanks for the replies guys, but I am not using a Pickit. I have setup my boards to match the pin layout of my U2 programmer. I just use a wire harness from the U2 to my boards. It's quick and easy that way.

What I meant about the sweeps is the status bar indicator. It usually fills about 3 times and then it would fail.

I don't know what the problem was, but I placed another 628A on another board and tried programming it. That worked. I removed the first PIC on the first board and replaced it with the second PIC. Tried to program the second PIC on the first board and it failed immediately, however, I found a very tiny solder joint between 2 pins and I removed it. Now it works fine.

Don't know if something was wrong with the first PIC or if there was a tiny solder joint, but I'll have to play with that PIC later. Don't know why it would run through it's sequence and then fail.

I'd post some code, but it's over 1000 lines. But with respect to errors in the code, the PIC would still be programmed with the faulty code and fail on run, not programming.

And yes, the correct PIC was listed in both programs.

Thanks again guys.

Tony

[Demon]

I figure it can erase and program just fine with the solder jumper, but then fails on the verify. Most likely why you see the status bar fill a few times then fail.

Robert
AKA Captain Obvious

[Art]

More likely it screws up the erase, and the programming as well, but doesn't know that until it tries to verify.

[ERMEGM]

OK, back to square one. Here's what I have. Obviously there is some interference with the signals.

My programming pins are connected to the appropriate terminals. RA5, RB6 and RB7 are being used, but they are being used as inputs, so they have a 10k pull-up resistor on them which gets pulled to ground when the tactile button is pressed (RA5), or the optocoupler is activated on the other pins (RB6 and 7).

When I try programming my pic on the completed board, it fails. When I program it on the board with just the PIC and header pins, it programs just fine. Is one of the components causing the interference? Anyway to isolate this or just redesign the board to not use those pins other than for programming?

Thanks,
Tony

[towlerg]

I don't know if its a typo but the 10k resistors on RB6 and RB7 are in series to isolate external circuitry. See 32028a, 91016b, 51474a etc.

George