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

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

Hi,
>     A solution with the resistive divider may be the attached one: if
>     the jumper is present, then the two resistors attached to the UPP's
>     PIC divide by two the voltage; the buffer is used to avoid problems
>     if the PIC-to-program draws too current.
>     Since a buffer is used, using an IC which packages four opamps,
>     another opamp may be used as a non-inverting amplifier with gain =
>     2; this way when you're programming a 2.5V PIC, the UPP-PIC gets
>     back TTL levels, instead of 0/2.5V levels.
>     The nice thing is that since the op-amps are always powered with
>     0/+5V, the UPP-PIC always get back 0/5V TTL levels from the
>     PIC-to-program, without the need of a further jumper.
>     I hope I was clear :)
> 
>     Something similar (not shown in the attached schematic) may be done
>     for PGC clock line (using a single opamp since that's not a
>     bidirectional line, AFAIK).
> 
>     How does it look?
> 
> 1: I am not going to change the hardware that much right now, let's 
> first investigate the resistive divider thing
> 2: the pins don't draw current, so we CAN use resistive dividers
> 3: stop doing so difficult, I don't want to use more components and 
> certainly no opamps / voltage regulators and all that stuff
ok ok; it's just that I have all hardware components at hand for building the 
UPP but since I have to use (in near future) a PIC24, I'd like to directly build 
an hardware version which can handle them.

So let me ask you 1 last thing; then I won't bug you anymore :)
when do you expect to be able to test/release the new schematic with the 
resistive divider?

Thanks,
Francesco

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