Solution for a COM port expander

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winterwind

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Need a board that use 1 COM port (DB9), out 4 or 5 COM ports, selection of any COM is performed by softwave and in that board use a micro controller AT98C51.
 

Re: COM port expander

COM port has 2 data lines and several control lines. What are you going to do with them?
Or, do you just want to have 3-lines in new ports: (Rx, Tx and GND)?
Full-duplex on all ports?
Baud rate?
...
Regards,
IanP
 

Re: COM port expander

Thanks IanP.
A problem, PC has only a COM, i can use modem, download cable for mobile, kit for microcontroller, ...
Once time, only enable a port, other ports disable. Port Selection are used by a switch on the board.
beside, use 3-lines, can need other lines to control.
Full-duplex on all ports. OK
Can select Baud rate by softwave.

Can you help me?
circuit schematics or related web.

Thanks
wind_winter05@yahoo.com
 

Re: COM port expander

More functional solution will be to get multi-port PCI card(s) and fit it to your PC.
They are not expencive (≈$20 for 2 ports: https://www.usbgear.com/2x-Serial-PCI.html ).
I don't think building serial port expander is a good idea ..
Consider the above ..
Regards,
IanP
 

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    winterwind

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Re: COM port expander

Hi Iand
you see web:
h**p://www.tanthanhdat.com/?action=content&show=article&cid=5&id=8
 

Re: COM port expander

I saw pictures of Port Expander - text undecipherable ..
You can build something like that; it does not look very complicated and microcontroller can be controlled, for example, through HYPERTERMINAL by sending to it simple command (SP1, SP2, ...) in ASCII .. and it will then activate relays and connect requested port .. one at a time ..
If you install a multiport card to your PC you will be able to operate all ports simulanously .. so if I were you I would just use a multiport card ..
Regards,
IanP
 

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