andrew12345678

I built my first programmer, and I went to test it with the software supplied on the site that i got the schematic from, however it is refusing to program my chip (Pic 16F88).

I had a look at the pin levels and found that MCLR is always sitting at +13V even when the program says it has been disabled, could this be the cause of the programming failure?

The procedure Im using is Start software, place PIC in socket, attach programmer to computer, power up programmer from an 18V power source, Erase All, Program all, Verify (Verify fails at 0000h, Read All (Returns hex data as 3FFF), Check Blank (Returns the PIC is blank).

The programmer I am using comes from www.oshonsoft.com/picprog.html

Any suggestions?

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"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

Nigel Goodwin

It's the rapid movement from 0V to 13V that switches the PIC to programming mode, if it's sat permanently at 13V then that's not happening.

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

andrew12345678

Would the powering up of the circuit cause that or does vdd have to be high for it to detect the rapid movement from 0 to 13V?

how could I fix this?
is maybe a transistor faulty?
for a temporary quick fix could i tie vdd high and then enable VPP and then burn the program?

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

SYE

Hi,
First check the voltage on pin 5 of the cable to see if the your PC is trying to switch VPP, if it is switching the problem is most likely the transistor (probably inserted wrongly in the board or blown).

andrew12345678

The voltage on pin5 is rising from 0.1V to 4.36V when VPP is enabled.
The Voltage on the programmer is sitting at 12.66V and rising to 13.41V when VPP is enabled.

So does that mean I need to replace my transistor?

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

Nigel Goodwin

There's a red LED on Vpp, this should ONLY light when you try and enter programming mode - so it should normally be OFF. Check the output voltage of IC1 buffer 4 - this should normally be around 12-13V, and go low (near 0V) when programming.

Did you buy it ready built, or make it yourself?.

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

eng1

That's correct.

No, it's working! it's not able to shut off... I would suggest changing the resistors (values) around it. You can do this test without inserting the PIC in the socket.

andrew12345678

Well, the LED is always on, i have only ever seen it off when the programmer has no power, I thought that was a bad sign.

I made it myself, designed the PCB and everything.

Ok, so i need to increase the resistor value of the resistor coming off pin 8?

what value do you recommend?

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

Nigel Goodwin

Presumably you did use an open-collector buffer chip?, if you used a normal buffer this is the effect you would get. Otherwise, check the voltage on buffer 4 output as I suggested.

I wouldn't suggest randomly changing values, and there's really no values that could affect your problem anyway!.

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

andrew12345678

hehe... funny you should mention that chip *tugs collar* its non buffering, I could only get hold of a Non-Buffering Hex inverter, no other inverters are available where I live, I hoped it wouldnt matter, and until now it doesnt seem to have mattered, I will check the voltage on that pin and get back to you.

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

andrew12345678

Ok, The Pin goes to 5.09V when VPP is disabled, and down to 0.04V when disabled, but the LED remains lit.

The chip I am using is 4HC04N if that helps

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

eng1

I don't agree.

But you might have found the problem, if that chip doesn't have open collector outputs...
Did you mean 74hc04n?

You have to get a 7406 (inverting) or 7407 (non-inverting).

andrew12345678

Damn, Damn, Damn!
Do I have any other options, because I cant get hold of that chip, and I really, really need to get it working tonight.

__________________
"The glass is neither half-empty, nor half full, it's just twice as big as it needs to be" - Unknown

Nigel Goodwin

It's ABSOLUTELY crucial! - it's what makes the programmer work, you MUST have an O/C buffer!.

If it's urgent to get it working, replace that single buffer with an NPN transistor, with a resistor feeding the base (say 10K), and another base to emitter.

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

Nigel Goodwin

In what way?, the relevent resistor values (the two 10K's) are in no way critical, and could be varied massively up or down without any problems.

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