I have to make an application configuration decision: Using USB CDC or RS-232?

In the lab I use a Tower system which offers both RS-232 and USB connectivity. It uses a FSShell component to communicate with a terminal on the host. Typically this is using an RS-232 serial cable connected to the host. Well, the challenge is that today most notebooks do not have a serial port any more. But they have USB.

So I ended up implementing both serial/RS-232 and USB CDC (Communication Device Class) support. Everything with Processor Expert components .

Selection between USB and Serial in the FSShell

Processor Expert in CodeWarrior for MCU10.2 is great in configuring the hardware and generating drivers. But in my case I need to switch between different operation modes of my hardware: either I use RS-232 or I use USB CDC. And this means different components and different settings .

On the software side I use #defines in my platform header file to configure the system:

#define PL_HAS_SHELL        (1)
  /*!< if we have shell support */
#define PL_USE_USB_SCI      (0 && PL_HAS_SHELL && PL_IS_TOWER_BOARD)
  /*!< if we route SCI through USB (CDC) */

So if I want to switch to USB CDC in my application, I turn that PL_USE_USB_SCI macro to 1. That works fine, except that way I cannot switch configurations in Processor Expert.

But wait, there are configurations in Processor Expert!

Configurations Folder in Processor Expert

If I create a Processor Expert project in MCU10, it already comes with a default configuration. I can rename it or add configurations using the context menu. That way I can create two configurations: one for USB and one for RS232:

USB and RS232 Configuration

I can create as many configurations I want, but only one is active at a time:

Selecting the Active Configuration

To add/remove components to a configuration, I simply enable or disable the component. If required I can have the same component multiple times in the project with different settings depending on the configuration selected:

Configurations Side-by-Side

Now I can switch between two configurations just with a mouse click. But what about my define for PL_USE_USB_SCI? Luckily there is a solution for this too .

The cool feature is that Processor Expert generates for each configuration a define. It is defined in the header file for the CPU component (usually Cpu.h). So depending on which configuration is active, it creates

/* Active configuration define symbol */
#define PEcfg_USB                   1U

or

/* Active configuration define symbol */
#define PEcfg_RS232                 1U

The define starts with PEcfg_ and uses the name used in the configuration. This allows me to rewrite my macros using PEcfg_USB:

#define PL_USE_USB_SCI      (defined(PEcfg_USB) && PL_HAS_SHELL && PL_IS_TOWER_BOARD)
  /*!< if we route SCI through USB (CDC) */

Changing Processor Expert configuration has now a direct impact on the components and automatically configures the user software part of my application. Neat!

Happy Configuring