Help wih design

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Hi everyone
I'm upgrading an existing embedded system.
This system has 1 serial port and DOS is runnig on it. But customers
wanted this device to talk with other 8 devices over RS232(new
requirement)

First idea i came up with is ; finding a new card with 8 serial ports
on it and integrate it to the former system.So that it would be the
interface between existing system and other devices.
But it costs too much(almost ~200$).


Another idea , maybe a fantasy , is finding a RS232<=>RS485
converter .Then plug it to the output of other devices .So i can build
a network . Then my application can successfully talk to others with
just some software upgrade.

Any ideas ?
Best Regards.


Re: Help wih design

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Good idea, but only half thought thru.

How would one of the external devices know you are talking to it ?

Each of the eight devices would need an address and someway to toggle
the direction of the RS485 line.

A small micro board with two serial ports attached to each device (
total of eight) would work.

One serial port talks to the local device and the other serial port
talking RS485 and handleing the addressing of the eight devices.

$200 / 8 = $25 per device and a RS485/RS232 comverter for the master DOS
system.

It might be cheaper and less programming to use the $200 solution.

Unless you can convince your customers to pay for the programming involved.

My $.02

donald

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