modifying PIC16F84A programmer to program PIC16F628A

[nisrine]

Hello Dude,

Please, I need your help with the following:

I have constructed the following PIC programmer for PIC16F84A.
(available in this site:**broken link removed**)

It works great with the software called NTPICProg and i have also tried to read the code using the IC-prog (i select it the JDM prog) and it worked.

My concern is to modify this programmer to program the PIC16F628A.
I connected pin 10 (RB4) to ground through a 8.2K resistor and tried to work on IC-prog1.6a, but it is not working. Error: Verify failed at address 0000h.

I removed the 8.2K resistor and tried PICProg4U and WinPIC800, I was able to program the PIC 16F628A (I set LVP to low, am i right?) but i cannot ERASE the code (it tells me erased but effectively it is not). YET i m able to erase the code in PIC16F84 :s

Do i have to apply more modification to this programmer ?

 

[whiz115]

16F628 and 16F84 as far as i know they are pin compatible... i don't understand why you are having difficulties.

 

[nisrine]

yes, it is true they are pin-pin compatible.

But i have read a lot of topics and docs saying that there is LVP and HVP and the programmers that we use for the pic16f84 cannot work directly with pic16f628a, because the pin 10 (RB4) must be grounded and stuff like this.

I tried to use the one i used with pic16f84, i succeeded when i have put the LVP fuse to low but i m not able to erase the PIC :S

I need your help

 

[blueroomelectronics]

That programmer is from an 8 year old Elektor magazine. JDMs are old and somewhat tempermental on a modern PC & OS.

 

[nisrine]

HI blueroomelectronics, you think that the problem is 100% from the programmer right ?

In general, can i program a 16F628A PIC without using the pin10 (RB4/PGM), or i must ?

 

[blueroomelectronics]

I don't use JDMs, that particular one seems a very poor design (and I think Elektor is an excellent magazine)
A more common version looks like this, but both are problematic. They require proper timing and high voltage on the RS232 port. (they are not really RS232 devices and toggle the data out on the handshaking lines)
**broken link removed**

 

[nisrine]

thanks,
the circuit you provided is for parallel port interface DTR (20) :S ? , what do they mean by the (20) ?

 

[blueroomelectronics]

No that's a serial port (an old DB25 shows you how OLD the design is), still it'll be a hit and miss design. What sort of PC / OS are you running. Is the serial port built in or a USB to serial device?

 

[nisrine]

P 4 / Win XP , serial port built in.
my concern is to program the pic16f628A and have a very small programmer (not a sophisticated one)

 

[blueroomelectronics]

The PICkit2 is an excellent programmer and very small.

 

[nisrine]

thanks again,
but i want to build a home -made programmer :S

 

[blueroomelectronics]

The schematic is part of the PICkit2 manual you can download from Microchips site. My Junebug has a simplified version in its manual available on my site. Both are USB enabled XP compatible and excellent development programmers / debuggers. I use mine (the Junebug) almost daily.
**broken link removed**My hand wired prototype

 

[nisrine]

oh! thanks a lot i will check it.
it will b great so i can program the pic and test it (of course if i plug it a test board) without removing it and placing it on the demo board, right ?

 

[blueroomelectronics]

Yes they are both ICD style programmers. You have to follow some rules to make sure your project does not load the programming pins and with some PICs you can also debug your circuit (an incredibly powerful tool)

 

[nisrine]

Thanks a lot blueroomelectronics, I will check it.

one more question (i think it is a stupid question), usually while working with usb, we will be facing more problems than serial/ parallel. Do this programmer needs any driver?

 

[blueroomelectronics]

It uses the HID driver built into XP, no problem. Serial RS232 & Parallel printer ports are fast disappearing from many computers.

 

[Nigel Goodwin]

one more question (i think it is a stupid question), usually while working with usb, we will be facing more problems than serial/ parallel. Do this programmer needs any driver?

You need to consider what's happening, with older programmers (like the JDM or David Tait style ones) the computer does the actual programming, the programmer is just a dumb interface - which is what cause the problems, as Windows doesn't like direct connections to the hardware, and isn't capable of doing accurate short term timings.

The USB style programmers (like the ICD2 and PICKit2) operate completely differently, they have a processor on-board, and it's that processor with does the actual programming of the target device, and is capable of far more accuracy that a PC. All the PC does is transfer the data to the programmer chip, which then does everything else.

So the USB connection is just a simple data transfer, as it's supposed to be, which is why it's pretty well problem free.

 

[nisrine]

Problem solved

Thank you all,
I have managed to solve the problem with no modifications the problem was from the software.