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Multiple RS232 ports


Is there a way to add multiple RS232 ports to a FEZ Domino? I see there is one shield, configured to access COM1 if my understanding serves me right. But how about adding a couple more RS232 ports?


There are 3 COM ports (UARTs) than can be connected to RS232. The one shield will easily give you access to COM1 but you can also connect the other 2 but not through the shield. You will need to do some wiring/soldering to make it work.

There are circuits that make this easier like this one for example



i am just new to FEZ but i like the idea of c# on microcontroller cuz its my favorit language.

I have a direct question to the COM Ports. You linked the RS232 with wires. But when i look at the documentations of my Domino, i cannot see where i should connect all cables to.

I am prety new to micro controller’s and the programming. So can you help me and explane where i plug in the cables so i have a new COM Port? (I know there is a shild for this but i need a second one…)

best regards,


Here is the document, wich device i want to connect to the serial port.

Would you might help me so i can understand how to connect it to the FEZ domino controller?

This is the doc

This board manages the complete communication and has a serial output. But can you give me a hand where i have to connect the 9 pins to?

RX and TX is DI0 and DI1… and the rest?

Or if you take a loog at this :
(But this is only a reader, i need to write aswell to the card with rfid…)

how can i connect this completly to the controller? (without the rs232 shield, using COM1 on the controller itselve DI0 and DI1)

best regards,


All this is found in the datasheet:

See page 1 and 2.


thx for the reply,

i just have seen my problem. Am i right that this modul is the base and i need the antenna for it on an extra modul?

So when i am right, for the communication with this device i need a second modul with a antenna where i put it in, wich controlls this rfid.

For the COM communication i also found the solution. Sry for this silly question. its my first develop on any microcontroller system. (But i am very firm with c#, the electronical side is my problem :slight_smile: ).

So the onliest thing i need to talk to a rs232 device is the power, ground and the rx and tx line. the other cables are device specific functions. Is this correct? (i saw your video and you also didnt connected something else. But if you wanted to send with your domino connected to xbee you need to connect the other com aswell, right?)

best regards,


Yes this is right. And about the antenna; you can have a look at the pin out. It has 2 pins for the antenna:

Yes. In my situation the Cobra is ONLY sending (tx) and the domino is ONLY receiving. For the domino to send I would have to connect a cable from COM1 TX (domino) to COM rx on the xbee.


thank you.

This helped me very much.

best regards,


You are welcome. Let me know if you have any questions left.