HDMI CEC in MXNet Mentor

HDMI CEC in MXNet Mentor

In order to send an HDMI CEC command from Mentor, we need to know the values for the following; SOURCE, DESTINATION, OPCODE.  Then depending on the Opcode being used, you may also need some additional parameters under the DATA field. 

SOURCE:
This will be a single Hex digit (0-F) that represents the type of device sending the command. (e.g., 1 = Recording device, 4 = Playback device, 5 = Audio System, etc.).

DESTINATION: 
Again, a single Hex digit (0-F) to represent the device we're looking to control.  In most instances it will be the TV that we're wanting to control, so we can either use 0, which is the CEC standard code for TV, or F which is a broadcast code.  Using a broadcast means that any devices in the HDMI chain should respond to the command.

OPCODE:
A two digit Hex code which represents the command you wish to send.  Some examples include;

04 = Image View On (used for TV on command)
36 = System Standby
82 = Active Source (Used to switch to a specific input)

DATA
In the case of OPCODES 04, and 36 above, no additional data is required.  This field can be left blank.  
For OPCODE 82, we need to specify the Physical Address for the input we wish to switch to.  This would usually be formatted as 1.0.0.0 for HDMI 1, 2.0.0.0 for HDMI 2, etc.


HDMI CEC is not a perfect standard, and different vendors will implement it in different ways, so there will inevitably be some trial and error involved in finding the correct commands for the specific devices you wish to control.  The attached spreadsheet shows common commands for turning on and off devices, which may be helpful for finding something that works with your particular device. 

The example below shows how we might turn devices on and off from a control group in Command Central.



This next example shows how we might switch from HDMI 1 to HDMI 2 on a TV