PICKit2 Vpp Low Voltage issue...

[Steve311]

Hello All; I am using the PICKit2 to program a PIC16F88. I have been encountering more problems than I normally do with verifying and connecting to the DUT during programming. I went through the troubleshoot option with the PICKit2 software and it seems my Vpp/MCLR line is only measuring 11.2V (that is what it says on the program, but with my voltmeter, I read 9.5V). This voltage should be 12V from what I understand.

Does this mean my PICKit2 is damaged? Has anyone else ever seen low voltage on Vpp and had success programming? I dont really want to purchase another one....any tips or insight would be greatly appreciated!

Thanks in Advance...
Steve L

 

[3v0]

Did you test VPP with the target disconnected ?

 

[Steve311]

Hi 3V0-- Yes I tested and did my troubleshooting without the PIC connected. The PICKIT2 was just simply connected to my usb port on my computer and not connected to any DUT.

What do ya think?

Thanks for your response.
Steve

 

[Wp100]

Hi,

Are you using a Desktop or Laptop and what is the USB +5v rail measuring ?

 

[Steve311]

I am using a laptop. The Vdd rail is measuring 5V (about 4.85 or so at the DUT)...

I have programmed many PICs using this same set-up so I know at one time, everything was working fine.

 

[Wp100]

Hi,

A few suggestions that might help, have seen these points mentioned many times on the Microchip forum where you might find a lot of help.
PICkit 2 FAQ

Just from your initial post it sounds as if you have had various problems for some time ..? - thankfully I've generally found it to be very reliable.

The points worth trying - a different USB lead, they did have problems with some, mainly not working at all.
Some laptop USB ports cannot supply enough power and a Powered USB Hub usually cures the problem.

You do not say if you are controlling the PK2 from MPlab or the PK2 V2.61 standalone program - do you get the same problem from both sources ?

Finally have you re - downloaded the OS to the PK2 v 2.32 ? - you can do it from either source - you just might have partially corrupted the program.

One final question, are you progamming the chip in circuit with any other components connected to the 3 programming lines ?

 

[Steve311]

Thanks for your reponses.

I did re-download the PICKit2 OS numerous times. I installed the latest version of the PICKit2 software.

I have successfully programmed numerous PICS using the same set-up I have now and never ran into this many issues.

I have an isolation cap between GND and MCLR, and I have a 510ohm resistor pulling MCLR to Vdd (I have had success with this resistor in the past).

One thing I don't fully understand is the actual purpose of the Vpp pin during programming. Is the 12V a critical path to a successful program?

 

[be80be]

One thing I don't fully understand is the actual purpose of the Vpp pin during programming. Is the 12V a critical path to a successful program?

on some it can be lower you should use a 10k for pull up I would say it a little hard for your programmer to pull a 510 ohm low it has to do that to

It uses a charge pump to get the 12 volts could have a bad cap in your programmer that would lower the output some the charge pump has 3 drops of .6 so if usb is 5 -.6 =4.4 x3 to get the 13 volts for programing you may have a bad one would put you in the 9 volt range

 

[Wp100]

Hi,

I have an isolation cap between GND and MCLR, and I have a 510ohm resistor pulling MCLR to Vdd (I have had success with this resistor in the past).

Well I am assuming you are talking about programming you 16F88 in its final circuit.
A 510R to +5 and a cap, 100nf? to 0v is wrong.


If you see Fig3.1 in the Pickit2 Users Guide it shows the correct components.

However to prove things are working correctly with the Pk2 and the 16F88 just make up an IC holder and connect direcly to the PK2 with no other components - just the 5 lines Vdd Vss Mclre PGC and PGD. That should program the F88 up fine.

Once you correct your ICSP components I'm sure it will work fine as well - but ensure there are no other components connected the the programming lines RB6 and RB7 and that nothing is pulling up RB3 the Low voltage programming line, if your target board has its own power on.


As far as I know, most common 16F chips work with 11-13v on Mclre to involke progamming mode.

 

[raviypujar]

My PICKIT2 is also giving the same problem and i got a solution for it check my blog

Please post the solution here, not link to your Blog.

Moderation.

 

[be80be]

This was a old thread every one wants to think that there pickit2 is not working and you need to do this or that to fix it. Well I'm sorry to say that 100% of the time it's not the pickit2 at all it's how you have the program pins loaded or hooked up.

VPP has to be-able to rise to program voltage which can be any where from 9 volts to 12.5 data sheet will tell you that information.
Likewise it has to be-able to pull it to ground.

ISP-data and clock need to be-able to toggle high to low.

Chips has to be-able to power up or be powered.

So first thing is to check your wiring two or three times.
Make sure the three program line can toggle high to low VPP MCLR, PGD,and PGC
And PGM is turned off in the configure word.

If you do all that you'll be a happy programmer.

 

[panic mode]

i agree 100% if this is original Pickit2 but i've also built a PICKIT2 clone (have to use the pic sample on something). clone originally had the same problem - it just would not work for 3.3V devices (even reading was working only sometimes). but it was easy to find that culprit was in the regulator for 3.3V (output was only 3.05V). i looked back at the components in the regulator circuit and found that wrong zener was culprit, i measured 3.6V instead of expected 4.3V (there is 0.7V drop through Vbe of NPN transistor). the bag in which zener arrived did show 4.3V part (grrrrrr). since i didn't have replacement with correct voltage, i lifted one side of the zener and added forward biased signal diode. that boosted voltage by 0.6V or so and now the 3.3V supply voltage actually measures 3.6V. it is a bit high but it works and i don't have to stress 3.3V parts with 5V.

 

[kyru27]

Maybe it's problem from the wires, I mean it's strange it's strange that it measures a different voltage from the one it's giving (though it has actually happened to me sometimes).

Have you checked the ICSP pins or the wire for the 9,5 V? If there's difference between them I guess it has to be a problem from the wires or something that is in your circuit that is getting some of this voltage.

Good luck

 

[sam_ecko]

Hi, i am new here and also have the same problem. I am trying to programme a 16f628A with my PICKIT2. I understand i cannot debug this chip without a header and so far i have connected it properly (to the chip on a breadboard). I have used both MPLAB and the programmer to try and burn my hex file. The PICKIT2 is not a clone, pins 1-5 are connected as they should and the only possible issue may be the wires on the breadboard used to connect the pins.

I have read a lot about the Vpp issue and will try try this later when i get home from work (i was wondering how vpp could be around 12v when the usb supplies 5v to the device?)

i can get the pickit to write seemingly succesfully on the programme software however when i try and read the hex for what i have just written it is mostly 3ffff. this is so frustrating!

 

[sam_ecko]

after the code has been written i it does not run...... its looks to have been ok in both mplab and the burning software however the circuit does not do anything when it is runing. (i powered up the chip while i was burning it). any help would be greatly appreciated, i have an icd2 which is now refusing to be recognised by my computer as well and this is all irritating me.

 

[panic mode]

if you have original PICKIT2 (not a clone) then chances of PICKIT2 malfunctioning are small. however, there is nothing preventing you from verifying that:
download software "PICkit 2 v2.61" from Microchip website. this is one handy program to have and should be used first to check if the programmer responds and does what it should. for example you can force signals on header so you can measure them with a multimeter (VPP, MCLR,...).

next thing is to make sure when connecting to target chip (PIC16F628A) you need to make sure that it is supported, and wired correctly.
if the wiring is correct, and target is ok, you can now read and write target, erase it, verify etc.

you should be able to read back same content that you write to target.

 

[Mickster]

(i was wondering how vpp could be around 12v when the usb supplies 5v to the device?)

A charge pump is used to generate the higher voltage required.

Look at the schematics in the PICkit2 user guide PDF:
https://www.electro-tech-online.com/custompdfs/2012/06/51553e.pdf

In Appendix B you will see the schematic covering 2 pages. U1 (18F2550) on the 1st page toggles pin 12 which switches Q4 (on the 2nd page) on & off rapidly, creating the higher voltage via L1 and other components within the pump circuit.

Go to the 2nd page and follow the schematic tag 'Vpp_PUMP' at the very bottom of the page to see which components are used.

Regards.

 

[sam_ecko]

still frustrated, but thanks for the fast replies.

thank you for your explanation and fast reply, i followed the schematic like you suggested. And i have the pickit software version 2.61 installed. I also calibrated the pins on the pickit and read 4v from the usb (pin 2 & 3) port.

When the pickit2 software tries to install my loaded hex it comes up with an error: 'programming failed at program memory address 0x000000'

i am still very confused... (and have bought a USB Microchip 40 Zif Pic EEPROM Programmer Kit 149) just in case i throw this thing at the wall...

(i also think i ruined 4 pics... )

Has anyone got this problem to work?

 

[kyru27]

4 V seems a bit off, if you do Tools-> Troubleshoot on Pickit 2 programmer it probably would tell you that voltage isn't enough, you can adjust it, so you pass the test and I'd recommend that you test the 5 pins there, if you happen to have all of them working properly it's strange you're getting an error.

Good luck.

 

[panic mode]

you can not expect it to work when voltages are that far off... test hardware and software first, before attempting to read and write target.

wait, did you say you read that from USB port pins 2 and 3? why would you do that?
those are data lines and you cannot measure this by just using multimeter....

USB power are pins 1 and 4.
or you meant something else? we can only help if we know what you mean.

programming port pins have various voltages which is what you should be testing.

this is how pickit2 looks like. if it is not this, it is clone. note descriptions: