[Usbpicprog-technical] Proposed schematic for future compat with 2.5V devices

[Francesco M. <f18...@ya...>]

Hi,
    as written in upp website (http://usbpicprog.org/?page_id=5) currently the 
UPP cannot be used with PIC24 and PIC33 series because of the TTL output levels.

I attach a sligthly modified version of the UPP schematic: here the PGD and PGC 
lines are attached instead to two PMOS instead of directly to the ICSP connector.
Through a simple jumper, the user of UPP can select whether to send 0-5V or 
0-2.5V to the PIC being programmed.

The 2.5V reference could be generated using a common LM317 or any other linear 
regulator.

Pull-down resistors on the drain pins of the two new PMOS may be necessary to 
ensure a good zero voltage level.

This should allow to use UPP to program also 2.5V devices, isn't it?
Do I miss something?

What about dynamic characteristics? I don't know which data rate should the 
clock and data line be able to handle...

THanks,
Francesco


PS: it would be nice to have an SVG version of the schematic in the website HW 
page, instead of the current medium-resolution PNG.

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