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UART redirect? (Beginner Question)

I need to access 3 devices via UART from one microcontroller, but I never need to access more than one at the same time.

Rather than finding a diesel uC with 3 UARTS, I was thinking of latching one UART output as necessary. For example, If I needed to access device 1 I would latch the tx/rx for device 1 and write to the UART. If I needed to write to device 2, I'd disable latch 1 and enable latch 2, then write. I'd be connecting at speeds of no greater than

19200 bps. I'm operating @ 5v.

I've never latched a serial connection. I want to make sure my latch has a good response time and will operate effectively at 19200 bps. Is there something specific I should look for? Should I just go with a uC or uP better suited for my needs?

Thanks

Reply to
Robert Bouillon
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Robert Bouillon wrote: ....

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Hallo Robert,

you could use a 74HC138 decoder for TX and a 74HC251 encoder for RX. Connect your uC-TX to /G2A and two select signals on the '138 and your serial data should appear on the selected Y-output. The '251 works more or less the other way round.

Regards Markus

Reply to
Markus Mandl

And make sure that you put in pullups or pulldowns so the transmitter goes to the right state when you're not switched to it (figuring out the right idle state is left as an exercise to the reader -- I think it's low on the RS-232 side and high on the TTL side).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply to
Tim Wescott

Or a (74HC perhaps)4052 quad 2 channel analog multiplexer - the digital lines don't 'know' they are being treated as analog! Just connect a couple of uC IO lines to the S0 and S1 (or A and B depending on data book), make sure the enable is active (low), don't forget to connect the analog ground as well.

Paul Burke

Reply to
Paul Burke

If you use MAX232s or similar, they have them already.

Paul Burke

Reply to
Paul Burke

Awesome. Thanks for the info. I'll give it a shot.

It's easy to forget the pull ups & pull downs so I'll make sure I get those.

Any idea how fast I'd be able to push the IC's? I'm worried that at some point they might not be able to handle the frequency, by either adding noise to the waveform or just getting too hot. I doubt I'd ever go above 38400 but it'd be good to know.

Thanks again!

Reply to
Robert Bouillon

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