16F877a programmer circuit problem.

[manz]

Hello


I am building the PIC programmer to download the program into my PIC using the serial port.

For the info, I am using PIC C compiler and WinPic800 (JDM programmer) software. I’m using the 16F877a (microchip) PIC.

I have experienced using the development kit programmer (from BIZ CHIP) and I’m trying to build my own programmer (based on the development kit) now but encountered some problems. The schematic are as below.

Situations:

1.The circuit did not detect the PIC that is connected to it (using the WinPic800 software).

2.The LED blinks while on the detection period and stops after it’s over.


I’m sure the problem is regarding the wiring (schematic) but I’m not sure where and what was it. I need anyone that is experience to have a look to my schematic and suggest on the best solutions. Tq for the help.


*I have read the entire (related) tutorial (from Nigel Godwin) but the programmer used in the tutorial is slightly different than what I’m building and the he uses different programming software.

Thanks again.

 

[Gayan Soyza]

Remove the LED & shift the MCLR 10K resister there. also your transistors collector & emitter in the wrong direction.Emitter must go to the RB7 pin.

 

[manz]

Gayan Soyza,thanks


I did the correction to the circuit but stiill the PIC cannot be detected.
is there anything else can be done to the circuit,well, firstly to make it run , then still using the LED so that there is some indicator that the circuit is running (detecting or downloading).

*i`ve tested the PIC (that i'm using) with the development kit and it's working fine.

 

[Gayan Soyza]

It might work use a 5.1V zenner & see.
Where did you place the LED ? Until work out don't use any LED's remove if you have one.

If it is not work even then need to check the voltages that is coming to the programmer as well.In most desktop PCs JDMs works well.

 

[manz]

i did not place any LED yet in the circuit. just like in the schematic (corrected) posted. for the info, the bzv 55c5v1 is a 5.1 zener diode, well, that is what i read in the datasheet .

or should i use any other zener diodes? any suggestion of what type? or should i just change to other zener diodes such as 1N4733A or 1N5231B or 1N751A. all of those are 5.1 zener diodes. which one do you think is appropriate?

just for the info, i am using desktop pc.

or is there any possibility the the resistor has been faulty due to the initial miss-wiring (the opposite direction) the circuit?

will the assembly of the circuit on the breadbord caused all of this problems since i'm testing it on the breadboard.

i have measured the voltage output from my serial port (connected and not connected to programmer circuit) and it is in the attachment.i do not know how you want me to measure it, and if its wrong, just let me know how.

i dont think the serial port voltage is the issue because i can use the serial port and the cable to be attach to the developement kit i've been using and it works just fine.The development kit is from BizChip as posted below.

any help would be highly appreciated.thank you.

 

[manz]

ok,i got this posted by you in other thread.it's the same circuit (uJDM programmer) im building but for different ic (PIC16x84). all the parts are exactly the same.

ok the question is that should i connect RB4,RB5 and RB6 of my 16F877a together as shown in the diagram?and can i use the WinPic800 programmer software to program it?

Thanks.

 

[Gayan Soyza]

Better do a hardware check. For this you need IC PROG

*Plug your programmer & open IC PROG.
*In that there is a hardware check tab. Go there & enable MCLR.
*Now measure MCLR pin voltage reference to VSS pin (Pin5).
*You must get more than 12V & check voltage across zenner it must show you 5.1V.

If this both voltages ok then your comport voltages seems to be enough If not you need an external VPP feeding circuit.

I suggest you to make that programmer in a vero board.Your zenner diode is ok & also your diagram.

Note that RB6 is the clock pin you need that pin this is one of five of ICSP pins.Other RB4, RB5 no need to connect.(But floating the pin PGM will meet some problems to some pics but not for this one)

After all this done you can program the pic in winpic800.
In winpic800 you need to select the programmer from its options tab.

 

[manz]

ok thanks.

i`ll have a try first and need time to check things out. i`ll let you know then.