MC55x4 – COM Port and their usage in MC55

Article ID: 94933218

Question

What is the COM Port usage in MC55

Facts

MC55 devices running different BSP’s and WM AKU’s

Answer

Many Motorola Enterprise devices use COM port 1 as the serial debug port; however, this is not the case on the MC55. On the MC55 COM Port 1 is used by the WWAN Radio.
Since the MC55 uses COM port 1 for WWAN connectivity any other application using this port prevents the phone from being turned on.


This Knowledge article applies to ALL the MC55 devices running different BSP’s and WM AKU’s

Application programmers need to be aware of the usage of the COM ports on the device. Below is a list of available COM ports, some which can be used in lieu of COM port1.
Applications need to be aware of a list of COM ports available on the system. Using of the wrong port can disrupt other applications designed to use that port.
For example, COM1 is used by the RIL driver to communicate with the GSM module.
If a tty application attempts to connect to COM1 while the phone is off, the connection is accepted.
The tty application works fine. However, if the user attempts to turn on the phone, the phone will not initialize. There is also no indication as to why the phone cannot be turned on.
Ensuring COM1 is not used prevents this from happening.
Similarly, if the phone is already on then trying to open COM1 using an application fails as the port is already in use.
Following is the list of available COM ports in BSP 27 of MC55.

User-added image

If we want to use COM ports above 9 we need mention $device. Please see the snippet below.
 
if (connectionInfo.LocalCOMPort > 9)
  CreateFile(TEXT("\\$device\\COM10:"),……………);
else
  CreateFile(TEXT("COM9:"),……………..);