A Question about the PICKIT/PK2LITE

[avi]

Hi All,
I'm designing a new portable device and I would like to use the PIC18F2550 as a USB programming interface to a PIC18F452.
I've seen in the PICKIT or the PK2LITE circuits an analog circuit connected to ICD pin# 1.
I guess it produces the 12v for programming level (some uses the MAX662 instead).
my question is:
if I already have +15v in the circuit, can I use it instead? and don't build the analog part?

Another Question:
because I use the PIC18F2550 just as a USB programming interface, do I have to program it?
I've heard that I may not do it, the PIC18F2550 has internal program for this purpose . is it right??

TIA,
Avi.

 

[Pommie]

The Pic18F2550 is capable of interfacing with USB. To be able to write code to do this needs a high level of ability.

I suspect, but may be wrong, that you have a USB programmer that you wish to use to program other pics. Please describe what you are trying to do and what hardware you have.

Mike.

 

[avi]

Hi Mike,

Hi Mike,
1) I have no programming HW, and you don't have to "suspect" me!
2) as I've written, I want to build a USB programmer like the PK2 ect...
I wonder what are all the analog transistors and FETs doing. and if I can omit this part by using an existed 15v.

TNX

The Pic18F2550 is capable of interfacing with USB. To be able to write code to do this needs a high level of ability.

I suspect, but may be wrong, that you have a USB programmer that you wish to use to program other pics. Please describe what you are trying to do and what hardware you have.

Mike.

 

[3v0]

Hi Mike,
1) I have no programming HW, and you don't have to "suspect" me!
2) as I've written, I want to build a USB programmer like the PK2 ect...
I wonder what are all the analog transistors and FETs doing. and if I can omit this part by using an existed 15v.

TNX

Mike may be gone for a while.

If you look look at the you will see that only transistor Q1 is used by the charge pump circuit to generate the hi voltage for programming.

Most of the transistors are there to switch between VPP(~12V),5V, and VSS to program run or reset the processor.

The only other type of solution I have seen is the stolz ICD2 version with an opamp.

EDIT: Erick used an adjustable voltage regulator in this thread.

 

[blueroomelectronics]

The "Trick" is getting the firmware on the 18F2550 in the first place.