Basic PicKit 3 Questions

[NorthGuy]

Hi,

Well my question now was if the PK3 can supply any power to the board. The wording of that one post sounded like you MUST have an external supply in EVERY case. I was assuming that very low power cases could be powered from the PK3 via the USB 5v power from the computer it is plugged into. Im pretty sure that's the way it works, but correct me if wrong.

It can supply some minimum power for your circuit, but you very rarely need it. I used it once or twice, more out of curiosity. Things that you make are going to be used somewhere eventually. And they will need their own power then.

 

[Nigel Goodwin]

Hi,

Well my question now was if the PK3 can supply any power to the board. The wording of that one post sounded like you MUST have an external supply in EVERY case. I was assuming that very low power cases could be powered from the PK3 via the USB 5v power from the computer it is plugged into. Im pretty sure that's the way it works, but correct me if wrong.

The PK3 can supply a small amount of power, BUT it measures the Vdd on the target PIC and won't attempt to program it if it's too low.

In my cases it reports Vdd as only 4.75V, and then does nothing else.

 

[granddad]

As posted .... PK3 will detect Vdd and / or supply Vdd if configured , so ICSP pin 2 has to be connected to the circuit supply .

 

[MrAl]

Hi,

So if you power your board with say a 7805 or LM317 or something and it already has +5v, you still connect Vdd to that +5v on the board even though the PK3 will not be powering it now?
That would mean the PK3 Vdd pin is bidirectional?

 

[Pommie]

I've never managed to get the pk3 to program anything without an external power supply.

Mike.

 

[Nigel Goodwin]

Hi,

So if you power your board with say a 7805 or LM317 or something and it already has +5v, you still connect Vdd to that +5v on the board even though the PK3 will not be powering it now?
That would mean the PK3 Vdd pin is bidirectional?

Yes, it has to read the Vdd in order to work.

However, 'bi-directional' isn't really the right term - it's connected to an analogue input inside the PK3, and also to the output of a voltage generator (so you can adjust the Vdd voltage (3.3v or 5v etc.)

 

[NorthGuy]

So if you power your board with say a 7805 or LM317 or something and it already has +5v, you still connect Vdd to that +5v on the board even though the PK3 will not be powering it now?

Powering or not powering, it detects the voltage. Once it sees the voltage it displays the "Target detected" message. Otherwise it stops working. It doesn't draw any substantial power from the pin, but it I think it does power the output buffer ICs.

 

[BobW]

On some occasions, I power the entire target circuit from the PICkit3, but these are generally circuits that have nothing more than one or two other CMOS chips, so the total load is very small. As others have mentioned, your final circuit is going to need a power supply anyway, so just make use of that if the PICkit doesn't have enough juice.

I moved up from the PICkit 1 to the PICkit 3 after getting to the point where the PICkit 1 wasn't able to program any of the new chips that I wanted to use. IMO, it was well worth the price. It was also an incentive for me to start designing my circuits to make use of in circuit programming, so that I wasn't constantly plugging and unplugging the chip whenever there was a program change. I did make a programmer board with a ZIP socket on it, but I'm using it less frequently these days.

 

[granddad]

For me it makes sense to include ICSP on a board , I started with diy Tait programmer and PIC16F84's and moved the chips around , when Pickits were a reasonable price I upgraded, don't understand why they ( PK3) are so expensive now , you would think MC would practically give them away . I always have an external supply . and a led on a pin to show my code is running .

 

[Nigel Goodwin]

I started with diy Tait programmer and PIC16F84's and moved the chips around.

I hope you used the MkII Tait derived design

David Tait was a programmer, not a hardware guy, so his original hardware was a bit bizarre (to say the least) - using CMOS switches to switch Vdd and Vpp. However, someone with a better hardware background soon improved it, using the familiar PNP transistors to do the switching

Interestingly, as well as talking to David via Email, I also used to talk to him on 2m amateur radio - I seem to recall he had a Trio/Kenwood portable (perhaps a TR2200 or TR2300?), and by placing it on top of two stools in a specific corner of his University lab we could contact each other

David was truly the 'father of home PIC programmers', and was probably the single person most responsible for their popularity with the hobby market.

You were a bit of a 'late starter' if you came in with the 16F84, the 16C84 was around quite a while before it's replacement

 

[granddad]

You were a bit of a 'late starter'

And a slow learner Actually The FPP program was great , I did make the 4016 version, and it was these switches got me into thinking about MiDi volume control with the 4067 (16-1) . One thing leads to another !

 

[Ian Rogers]

You were a bit of a 'late starter' if you came in with the 16F84, the 16C84 was around quite a while before it's replacement

I was using the pic16c71 for quite a few jobs... I already had an eraser so re-programming wasn't a big deal... I remember with picstart programmer I had to jam a resistor in to pullup the MCLR ( recomended fix ) when I started using the F range...

 

[Nigel Goodwin]

I was using the pic16c71 for quite a few jobs... I already had an eraser so re-programming wasn't a big deal..

Except the 16C71 was EPROM of course, whereas the 16C84 was EEPROM - hence it's huge popularity. It wasn't until the 16C84 was replaced by the 16F84 (also an EEPROM device, just a later silicon revision of the C84) that they created the scheme of C for OTP/UV and F for EEPROM devices.

I seem to recall that the 16C71 had A2D?, was it the first one to have that? - I've never used one, but I have used 12C508's, and have a JW erasable one somewhere.

 

[Ian Rogers]

I seem to recall that the 16C71 had A2D?, was it the first one to have that? - I've never used one, but I have used 12C508's, and have a JW erasable one somewhere.

That's why I had them... It had 4 ADC pins... I got into pics when we hacked PS1's ( am I allowed to say this now ) the mighty pic12c508 spewed out the frequency that original discs spewed out!!...I still have the program somewhere...

 

[Nigel Goodwin]

That's why I had them... It had 4 ADC pins... I got into pics when we hacked PS1's ( am I allowed to say this now ) the mighty pic12c508 spewed out the frequency that original discs spewed out!!...I still have the program somewhere...

You were a bit later than me then

I first came across PIC's when they were used for pirate TV cards for Analogue Sky TV - initially OTP ones were used, then when the 16C84 was released I took notice, as I thought what a useful device it could be!

That's when I originally came across David Tait's programmer design, and I wrote the first revision of PicProg, and a year or two later the first version of WinPicProg.

Funnily enough, while I was never involved in the pirate Sky cards, a good few years later a guy came in to work and asked if we'd like some boxes of electronics gear - which was in a small factory he had taken over. We said we'd take them and send them for recycling if nothing else - main items were an old storage scope (which we gave to a friend, and he donated to the original manufacturers museum), and a box full of blank pirate Sky cards plus a couple of hundred blank OTP PIC's for them (which I gave to a member on here), and a few other PIC bits and bobs.

 

[Ian Rogers]

I remember SKY sending signals to destroy them... A friend of mine had a card with a pic micro inserted into the old analouge sky box.... A serial lead to his PC... Sky then asserted a voltage in the card destroying the pic AND the serial port of the PC... You got to laugh!! I think he's still trying to rob everyone....

 

[atferrari]

I remember SKY sending signals to destroy them... A friend of mine had a card with a pic micro inserted into the old analouge sky box.... A serial lead to his PC... Sky then asserted a voltage in the card destroying the pic AND the serial port of the PC... You got to laugh!! I think he's still trying to rob everyone....

IIRC, that made for several articles in Radio Electronics.

 

[Nigel Goodwin]

I remember SKY sending signals to destroy them... A friend of mine had a card with a pic micro inserted into the old analouge sky box.... A serial lead to his PC... Sky then asserted a voltage in the card destroying the pic AND the serial port of the PC... You got to laugh!! I think he's still trying to rob everyone....

I suspect that was actually an urban myth

Also, if he had a lead to a PC then he wasn't using a PIC, he was using the PC to decrypt the signal, and just a simple card interface.

As the only connection to the PC was through a MAX232, nothing Sky could do would damage it - even assuming they had the capability of switching a higher voltage to the card interface, which I seriously doubt.

I suspect your friends problem was down to lightning or static damage.

 

[Ian Rogers]

Probably!! This guy's honesty and integrity isn't the best...

I thought I smelt a bit of billy when he told me....