Supporting multiple architectures with shared source code in MPLAB.X v6.00

Here's a technique for creating mulitple projects in MPLAB.X that share a body of source code. In this example, we'll create a simple "blinky" app that runs on both the SAME54 XPRO and SAML22 XPRO development kits.

• Create a “wrapper” directory, e.g. mplab_multi_arch
• Within that directory, create an MPLAB project for each platform, e.g. "SAME54" and "SAML22"
• In each MPLAB project, rename the default configuration to <platform>_config
• Use Harmony 3 to instantiate and configure the various modules for each project.

You will end up with a directory structure like this:

mplab_multi_arch/
  firmware/
    SAME54.X/
    SAML22.X/
    src/
      config/
        same54_config/
          driver/
          peripheral/
          definitions.h
          ...
        saml122_config/
          driver/
          peripheral/
          definitions.h
          ...
      packs/
      app.c
      app.h
      main.c

The important thing to note is that some src/ files are shared among the projects, but within the src/ directory, the config/ files are segregated by platform (technically, by configuration).

Since you want all application-level code to be independent of the underlying platform, you might want to create a bsp/ directory to isolate the application code from MPLAB-specific library calls. And it might look like this:

src/
  bsp/
    bsp_led.h
    bsp_led.c
    ...

Within the bsp_* files, you can provide bits of platform-specific code like this:

#if defined(XPRJ_same54_config)
  ...
#elif defined(XPRJ_saml22_config)
  ...
#endif

But if you find that there are too many #if statements cluttering up the code, you can create shared .h headers and split the .c code in to common and platform-specific files:

src/
  bsp/
    bsp_led.h
    bsp_led_common.c
    bsp_led_same54.c
    bsp_led_saml22.c

The magic that makes this approach work is MPLAB’s “Exclude File from Current Configuration” feature. The same54 project would exclude bsp_led_saml22.c and the saml22 project would exclude bsp_led_same54.c.

• This approach gives us a flexible approach to sharing code without having to write custom preprocessing scripts.
• It takes advantages of built-in features of MPLAB and Harmony 3.
• It lets you use #if / #ifdef sparingly where needed.
• But if your code is getting too cluttered with #ifdef’s, there’s a simple mechanism to control what source code is compiled and included in the SKU’s project.

• It ties you to MPLAB. This may be a non-issue: if you ever needed to switch to (say) an Eclipse-based IDE, Microchip might provide migration tools.
• If you use Harmony to create a configuration for SAME54, there’s no clear path for using that configuration (with tweaks) for SAML22. This is not specific to the approach described here: the problem is intrinsic to Harmony. There may be a tricky way of copying .yml files from SAME54.X into SAML22.X without mangling things, but I haven’t investigated yet.