JDM Voltage

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GatorGnet

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I know a lot of people, including me, have had some issues with some serial ports not supplying enough voltage for the pic to program. After going over some programmer schematics, I wanted to see if it would be possible to modify a jdm design and add the high voltage to Vpp using an external power supply? I know this isn't 100% properly connected but I wanted to give the idea. Any thoughts?

Simple JDM:
**broken link removed**

Example add on:
**broken link removed**
 
Why not just use one of the many already modified schematics on the net? - but even then it's still a rubbish programmer.
 
I agree but this would be a quick build and it gives me another project to mess with. I am ordering a better programmer anyways but wanted to see if this would work?

Could the one above work as I showed or would I have to change more?
 
Like I said, compare it to existing designs, there are a number of them - I've never tried a JDM, and WinPicProg specifically doesn't support serial port programmers purely because of the JDM's unreliability (even though adding serial port capability would be trivial).
 
The P16Pro seems to be a better design but I am missing the 74LS05 from my inventory so I would have to wait until I ordered it. I have some projects I would like to finish this weekend.

Also, are the 74LS05 and 74LS06 similar/interchangeable? I have found more then one schematic for this style of programmer and it uses both.

Does the programmer need to be as close as possible to the port or can I make a 2 foot or so cable to it?
 
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They need to open-collector buffers, either inverting or not, you can set the type in the software.

7406 or 7407 are the two usual alternatives.

Does the programmer need to be as close as possible to the port or can I make a 2 foot or so cable to it?
Click to expand...

The cable from computer to programmer seems to be no problem (I always use a 6 foot lead to a parallel port switch, then another 6 foot lead to the programmer). ut if you're doing ICSP then the leads from the programmer to the target need to be VERY short (cm's not inches).
 
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