Need help multiplexing EUSART output

[Kamikaze47]

or two series resistors, one to each addressed device ... and grounding ( or VCCing ) the signal ( past the resistor ! ) with another PIC pin , if NO transmission, and use the PIC pin as an input for transmission.

may be too simple ?

I just did a few tests. This idea seems to be working. The signal would not get through the series resistor until i reduced the value to about 200 ohms. That means a 25mA draw whenever the signal is low. I guess that's not too bad.

[Kamikaze47]

The only thing that worries me is the possibility of reduced reliability due to the series resistors.

[Acetronics2]

74ls 425/426 ???

[Kamikaze47]

Cant seem to find any info on the 74LS425/426 chips.

But I think i'll pick up a 74LS139. The data sheet says its designed for high speed data, so it should be perfect.

I still have no idea why my circuit in my OP does not work tho. As far as I can tell, it should.

[ardhuru]

How outlandish is this idea?

I notice you only want to transmit, not receive.

So, how about sending the same data to *both* your recipients, with an extra starting character that acts as a qualifier that decides which of the recipients would accept the data as valid? Assuming, of course, that you are in a position to modify the code at the target units as well.

Regards,

Anand

[mister_e]

Maybe because the 2 units can't be altered... my own and personal guess

[Kamikaze47]

Unfortunately I can't change the code of the targets.

[ardhuru]

How frequent would the changeover(s) be?

If not too often, how about using a small relay with its n/o, n/c contacts?

Anand