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I've attached the first cut of a schematic for a possible Xcat NG for

> the original X. With the appropriate firmware it will retain all of
> the features of the legacy Xcat.

Skip,

You're _way_ better at this than I am.

Questions to help me understand the magic:

1. You'd mentioned SN74LVCH8T245 bus transceiver / level shifter chips.
You did this circuit with SN74LV244APWR instead because the address
lines are always outputs, and the data always inputs, and you don't need
bidirectional translation, right?

2. You only have pull-ups on the address lines. This is because the
outputs need to be lifted, but for the inputs, the '244 chips are 5V
tolerant?

3. You don't have pull-ups on A8 and A9, Mode 6, or COS. Pretty sure I
don't understand this.

4. We're getting 3V3 from the RPi?

5. The 'LV244 doesn't seem to be available in DIP?

Thanks for all of your effort!

De

You're _way_ better at this than I am.

I've probably just had more experience. I started out life as a hardware guy...

Questions to help me understand the magic:

1. You'd mentioned SN74LVCH8T245 bus transceiver / level shifter chips.
You did this circuit with SN74LV244APWR instead because the address
lines are always outputs, and the data always inputs, and you don't need
bidirectional translation, right?

Correct (and I just copied it from the C64 project).

2. You only have pull-ups on the address lines. This is because the
outputs need to be lifted, but for the inputs, the '244 chips are 5V
tolerant?

3. You don't have pull-ups on A8 and A9, Mode 6, or COS. Pretty sure I
don't understand this.

Both of those are Syntor X weirdnesses and something we missed in the
legacy Xcat, there are pullups on A0->A7 in the Syntor X code plug but
not on A8, A9. Maybe it's an F8 thing.

4. We're getting 3V3 from the RPi?

Yes, there's a regulator on the Pico, I'm kind of assuming there's
enough head room to be able to power our level translators (and it's
also something I "borrowed" from the C64 project).

5. The 'LV244 doesn't seem to be available in DIP?

I haven't gotten into the physical aspects of the board yet. DIPs are
getting rare, The larger surface mount parts aren't all that hard to
solder, but certainly changing out parts for buildability is something
to look at before Dave starts laying out the board.

Thanks for all of your effort!

This is the first schematic I've done in years ... it was fun learning
a bit of Kicad.

Thanks for looking!

73's Skip WB6YMH

De

3. You don't have pull-ups on A8 and A9, Mode 6, or COS. Pretty sure I

> > don't understand this.

> Both of those are Syntor X weirdnesses and something we missed in the
> legacy Xcat, there are pullups on A0->A7 in the Syntor X code plug but
> not on A8, A9. Maybe it's an F8 thing.

I think part of the answer to A8/A9 can be found on PDF page 11 of the
F8 data book I uploaded to the files area the other day: they're on port
1, the others are on port 4. (The rest of the answer is probably locked
up in the way the firmware sets the output buffering.)

It looks like Mode 6 has pull-ups in the radio.

And COS is an input?

> > 4. We're getting 3V3 from the RPi?

> Yes, there's a regulator on the Pico, I'm kind of assuming there's
> enough head room to be able to power our level translators (and it's
> also something I "borrowed" from the C64 project).

Pico datasheet says it can probably do 300mA. The '244 sheet seems to
indicate that a typical current is 16mA. There would seem to be plenty
of headroom.

De

On Fri, Aug 12, 2022 at 7:22 PM Dennis Boone <drb@...> wrote:

> > 3. You don't have pull-ups on A8 and A9, Mode 6, or COS. Pretty sure I
> > don't understand this.

> Both of those are Syntor X weirdnesses and something we missed in the
> legacy Xcat, there are pullups on A0->A7 in the Syntor X code plug but
> not on A8, A9. Maybe it's an F8 thing.

I think part of the answer to A8/A9 can be found on PDF page 11 of the
F8 data book I uploaded to the files area the other day: they're on port
1, the others are on port 4. (The rest of the answer is probably locked
up in the way the firmware sets the output buffering.)

It looks like Mode 6 has pull-ups in the radio.

And COS is an input?

Yes. When enabled the Xcat sends a CI-V packet everytime the squelch
opens or closes along with the channel. I used that to update the
title bar of the Windoze app so it would show what mode it was
listening to when scanning was enabled. It's probably not something
for a "real" CI-V bus with multiple radios, but it's handy.

> > 4. We're getting 3V3 from the RPi?

> Yes, there's a regulator on the Pico, I'm kind of assuming there's
> enough head room to be able to power our level translators (and it's
> also something I "borrowed" from the C64 project).

Pico datasheet says it can probably do 300mA. The '244 sheet seems to
indicate that a typical current is 16mA. There would seem to be plenty
of headroom.

Excellent! I hadn't looked, that make me feel better!

73's Skip WB6YMH

De

Yes. When enabled the Xcat sends a CI-V packet everytime the squelch

> opens or closes along with the channel. I used that to update the
> title bar of the Windoze app so it would show what mode it was
> listening to when scanning was enabled.

Ohhh, it's coming back to me. I mad xcatctl's `cosmon` for listening
for these.

De