Hi,

I'm new to PICs, and to get myself started I built the JMD serial PIC programmer, but when I try to program a 16F84A PIC, I get the error "Verify failed at address 0000h !".

I think i've tracked the problem to the programming voltage. During programming, the _MCLR pin is only at 6.3v.

Anyone have any suggestions?

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Mostly Harmless

 

Use a parallel port programmer instead!, the JDM is well known for it's problems.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I would, but my PC doesnt have an avaliable parallel port.

So i'm kinda out of ideas

__________________
Mostly Harmless

 

Either use a 'proper' serial port programmer, although these are the most expensive ones!, or search the internet for varients on the JDM programmer - there are lOAD'S of sites with improved versions, basically providing it with a proper power supply.

If you're using a laptop that could well explain your problem, the JDM programmer relies on the computer having an above spec serial port, and laptops are usually way below RS232 spec.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

6.3V is seriously low, you need to measure between MCLR and the pic's ground connection (pin 5). not to the Pc's ground.
If you realy have only 6.3V that would mean your pc's serial port output is between -3 and +3 volt, no pc has that low values.

 

I am measuring the voltage between Pin 5 (GND) and Pin 4 (_MCLR).

I thought it was strange that I am only getting 6.3v... I dont know whats wrong. I'm not using a laptop, just a standard desktop PC.

Nigel Goodwin: I cant find any schematics for a serial programmer with power supply. Do you have a link?

Thanx

__________________
Mostly Harmless

 

have you tried another computer yet?

Also try measuring the serial port's voltage without the programmer connected. If it is much higher then +3 / -3V then there's probably an error in your programmer wich pulls the ports voltage down.

 

There are details on the original designers website, try http://www.jdm.homepage.dk/solution.htm.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

When i check the voltage from my serial port while the programmer is unplugged, i get +11.6v and -11.1v

so does this mean theres something wrong with my programmer?

__________________
Mostly Harmless

 

I've found the problem. One of the transistors was faulty :roll:

I've replaced the transistor, and now get 13v on _MCLR, and the programmer works perfectly.

Thanks for your help guys.

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Mostly Harmless