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bristan8
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Joined: 13/11/2017
Location: Australia
Posts: 16

Posted: 04:29am 14 Dec 2017

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Hi, I recently obtained a pickit 3 and built a little universal icsp board with multiple pin connections When I first tried it I got an error message so I tried to program the 16f88 on a prototyping board with direct pin connections. It also gave me an error until I found out that I had to enable power from the tool. When I changed this setting this system then worked. When I then retried the universal board with the new power settings I got an error saying that vdd was only 4.75v. I then changed the power setting to 4.75 v and the unit worked however the note was that 5 v was recommended.
Being new to this my question is does it matter? Will it work ok at 4.75v Or do I have to provide an additional power supply to the board. The direct wired setup worked ok without reducing the vdd setting

Azure

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Joined: 09/11/2017
Location: Australia
Posts: 446

Posted: 04:45am 14 Dec 2017

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When you try and power your processor for programming using the PicKit you need to be aware that in most cases you are actually powering the whole 5V rail on the target system as well. Depending on your target system voltage regulation and total board load this can be to much for the PicKit and the USB port it is plugged into.

If that is the case use an external supply for the target.

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9750

Posted: 06:58am 14 Dec 2017

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Unless you are ONLY programming the target device - and NOTHING else such as what Azure is hinting at, then you should not have any problems. As soon as you add other circuit into the mix, the PK3 often does not have the grunt to power the auxiliary stuff, so will throw that error in IPE - if I may paraphrase Azure for a moment. Just as Azure suggests, if you use an external 5v(or 3v3 or whatever the chip needs) supply, you should not have that problem. The PK3 and IPE are notoriously pedantic about the voltage needing to be spot-on. They probably have a point, I suppose.Edited by Grogster 2017-12-15

Smoke makes things work. When the smoke gets out, it stops!

bristan8
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Joined: 13/11/2017
Location: Australia
Posts: 16

Posted: 08:05am 14 Dec 2017

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I am only programming the target device. The circuit I made is designed for a number of different pics so there are more than five connections to the pic. According to the designer this is ok as the 'spare' pins are only analogue or
dig inputs. This must be reducing the voltage to the chip itself. When I try it With only five connections to the pin my usb output is sufficient. I obviously didn't make it clear that I only made a programming board and there is no other circuit attached. I mainly wanted to know whether it would work with 4.75v as it would be a pia if I had to add power . It would be easier to make another small board with just five connections to the 16f88.
http://picprojects.org.uk/projects/progadapt/index.htm

Azure

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Joined: 09/11/2017
Location: Australia
Posts: 446

Posted: 11:16am 14 Dec 2017

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In reply to your previous question. The answer is uncertain as it will depend on the actual tolerances of the device being programmed. Also whatever is causing the voltage drop may not be constant in all circumstances.

If you have only put in minimal wiring for programming and there is only the processor to be programmed then there should not really be anything putting a load on the PicKit to cause it to error with a voltage drop.

Things that can effect this are the wiring/pcb tracks, quality of sockets/connectors, build quality of PCB (solder/flux residues) and any other components loading pins or power rails.

If you want to post a picture of the assembled unit and the schematic we might be able to offer suggestions.Edited by Azure 2017-12-15

bristan8
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Joined: 13/11/2017
Location: Australia
Posts: 16

Posted: 08:44pm 14 Dec 2017

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To azure, see the link in my previous post. I built the stripboard version. I have since received info that programming spec vdd range is 4.5 to 5.0,so 4.75 is ok.

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