The standard QML Viewer/TIO Agent/SIO Agent serial port architecture was developed for use cases where the display module is connected to an external intelligent device such as a microcontroller that sends and receives ASCII data messages. This will not work well if your external device needs a binary protocol or if the display module needs to be connected to more than one communication port. In these cases, you will need to write your own Custom IO Agent.
In the Simple IO Agent Demo the IO Agent connects to two serial ports: the standard RS232 port (DB9 on the G2C1 Development Kit) and a USB-serial adapter (FTDI type as provided with the G2C1 Development Kit). The supplied QML example can send a message to either serial port and receive messages identified with each port.
If you need help with this, contact Reach Technical Support.
To have full control of everything, you may want to write your own IO Agent to connect to the QML Viewer on one side and the I/O port(s) on the other.