PIC16PRO40 Problem

[theinfamousbob]

(Mods: I know this doesn't really belong in here but I didn't want to post it in projects/uCs/anything else...didn't want to confuse people etc.)

Here's the problem -

I built it with the schematic off of Nigel's site (which is soooo nice btw), connected it and voila! Verify errors at address 0x000. I know that means something's wrong with the circuit because it's not even taking the write. I'm thinking my problem is the 330pF cap that connects between a couple of the PIC lines and ground...the smallest thing i have around is a "102" ceramic disc cap (isn't that a .01mF?) I'm trying to program a 16F628A (I guess like the tutorials...I should really get a PIC w/more I/O lines for my CNC mill...otherwise I'll need 2 628s and will probably go to 3 - one for each axis...).

Any advice would be appreciated....thanks.

 

[Nigel Goodwin]

102 is 1000pF, probably too high - try leaving them out all together - they are usually only added if you have problems (just checked two programmers here, neither have them fitted).

Check your PSU, it needs to be about 18V and low ripple, and ripple making it through the regulators will stop it working - try two 9V batteries in series, I use them all the time.

Other thing, try increasing the programming delay, it's 10mS by default, but following recent XP upgrades I've had to increase it to 12mS on a PIII and 15mS on a P4.

 

[theinfamousbob]

I'll have to try adjusting the delay. My power supply (although it's quite cheap) is labeled 12V @ 500mA...my meter showed that it was putting out about 24 volts...

Thinking about the design, I had to mod it a little. I didn't have any 7808s around so I used a 7805 and 7812 with 1mF polarized caps between power in/ground and the out/ground to help with drift/ripple. I'm going to try redo-ing the power supply area of my board after I pick up a 7808 and see if the +13V helps...(sorry I didn't post about my power supply mod before...I didn't think of it and at that point in time I was running on 5 hours of sleep, after being awake for 16 hours...and I'm not even in college/university yet...)I'll try the 9-volts too and see if that helps also.

When it's all said and done I'll post some pics of it.

Thanks!

 

[theinfamousbob]

...back again.

I rebuilt the circuit with all new parts (just to be sure) and still no luck. I'm running the proper regulator circuit, outputs just fine. Some testing on voltage drops and I found the Vdd transistor is only putting out 3.5 to 4 volts. Is this normal? My guess is that'd be closer to 5, so that might be the problem.

I have the programming delays set in the 20ms range, and am using two 9v batteries to power it. It's breadboarded, and nothing is jumping. Maybe it's just the cheap RadioShack transistors? (asst. PNPs)

 

[Nigel Goodwin]

Your Vdd sounds far too low - are you sure you haven't connected the transistors the wrong way round?, sometimes they have diferent connections.

 

[Gaston]

i built this board myself and i had a lot of problems ( all of which were my fault) i found a logic probe to be indispensable in getting it to work. i just started at one end of the schematic and went through to the other checking every spot for the proper signal. it took a while but it works now and i haven't had any problems.