Atlona Help Center

KB01085 - I am unable to get RS232 to pass from the Master RS232 input of the AT-UHD-PRO3 matrix and out from my HDBaseT receiver (to send RS232 commands from the matrix to a display)


Scenario: I am attempting to pass RS232 through my UHD-PRO3 matrix to a display/projector located at my output zone. I am not getting any response from my display when I send commands through the Atlona system.

Troubleshooting: If you are having trouble getting RS232 to pass through the matrix to control a display, we recommend testing in the following way:

To test the display/projectors ability to accept RS232 commands:

  • Are you able to control the display/projector locally by sending it RS232 commands directly from a serial program or control system?
  • If you can control your display locally, please note the port settings required for the connection to your projector (that you just tested and confirmed worked) and mirror those settings in the UHD-PRO3’s “Control Settings tab” in the web interface:


  • If you cannot control the display/projector from a local connection, we recommend contacting the manufacturer and seeing if there are any requirements to get communication to pass. Otherwise please check your RS232 commands and port settings.

If you are able to control your display/projector locally but not through the Atlona matrix:

  • Please make sure you are using the correct RS232 ports on the Atlona matrix (you will need to use the MAIN port):


  • Are you able to communicate with the Atlona matrix through RS232? (i.e. Can you turn the matrix on and off using RS232)?
  • If yes, see below 
  • If not, let’s test this connection further: Please confirm you are sending commands to the Atlona system with the following port settings: Baud rate: 115200, Data bits: 8, Parity: None, Stop Bits: 1 and Flow Control: None. Also please note your Comm Port (found in device manager)
  • If data is still not passing, try installing a null modem adapter on the RS232 cable or simply flip the TX and RX pins at the Atlona RS232 port.
  • Please try this to confirm we are able to communicate with the Atlona locally.
  • You can use these free serial programs for this test: serial program for PC's and serial program for MAC
  • For example, your HTerm connection should be like so when sending commands to the Atlona matrix:   
  • If you are unable to communicate with the Atlona and your display locally, please check your RS232 cable connection and baud rate (should be 115200). See if you are able to control another device by connecting this same cable to it. The TX pin of your RS232 cable will go to the RX pin on the matrix and RX pin of your RS232 cable to the TX pin on the matrix.
  • Please note Atlona devices require the use of a carriage return after a command is sent (each control system has a different method of sending carriage returns so please refer to your specific system's settings). For more info on carriage returns, see this article
  • If you are able to locally control your display and projector, please confirm the port settings for the specific HDBaseT output are configured to match the specifications of your display. Port settings can be changed via RS232 or through the web interface of the matrix (see screenshot at begining of article)
  • Once port settings are checked and confirmed to be correct, please make sure you are using the appropriate “RS232zone#[]” command. The # after “RS232zone” will be where you enter the number of your HDBaseT output to control (i.e. RS232zone3 = HDBaseT output 3). The square brackets (“[ ]”) after RS232 zone refer to where you enter your displays specific RS232 command. Therefore, a command to control a projector connected via HDBaseT output 2 and that can be turned on via command “PWON” will be turned on via “RS232zone2[PWON] + carriage return”
  • If you are able to control the Atlona matrix and your display locally but are still unable to control a display through the matrix, please try the following: On the HDBaseT receiver, short the TX and RX pins to each other (you can use a paperclip or a small wire). After that, let’s send a command to the matrix and specific HDBaseT output port. We should see the command being sent come back to us as feedback.

If still having issues in getting RS232 to pass, please contact Atlona Technical Support for more assistance.

 Article ID: KB01085 


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