开云体育

on your point four Roger, how about a couple of I2C parallel ports or shift registers on the RF deck to drive the relays, a significant reduction is connections between boards...

I've used 74HC595 for LED displays (driving ULN2003s).? I've wondered about these, and given the low switching frequency, it's an option.
By moving the pins around (and using the MCLR for the tune button) I've got the frequency input sorted without changing the functionality.
I was hoping to lose the I2C for the display, but I'll probably need that for an external EEPROM.

So have the two buttons, and the two LED pins to play with.? So probably enough to add an extra relay for the inductor chain, but not too much more.

For the remote unit, I'd prefer to use differential signalling (something like RS485) to avoid noise problems on long lines.
For DMX lighting I've used the PIC comparators on the receive side, and a CLC block to invert the Tx pin, to get a RS485 like Tx.
This will need 6 pins (for PICs without PPS) or 5 pins (on PICs with PPS).

The high end tuners have 9 capacitor relays, 9 inductor relays, with 5 output capacitor relays, so 23 channels, that's 8 more than currently used.
The 40/44pin version of the PIC is the easy option, they are only about US$0.50 more, and is a lot less messing about than using external chips.
They have 12 extra I/O lines, so enough even for the biggest config.
The remote version would lose the local buttons, so that would give the 6 extra lines needed for the differential signalling between the units.

Looking at the pins required for remote unit (in-shack):
? 5-pins for the differential Tx/Rx interface (assuming a PPS device)
? 3-pin for the buttons
? 2-pins for the oled/LCD
? 2-pin for the Red/Green LED
So this could use a 14-pin device (something like a 16F15325).
? For the Icom/Yaesu/Kenwood it would be easier to use a 20-pin device (something like a 16F15345)

Roger.