Adding and Assembly file to an mbed-os v5 project

Hi, I’m having a bit of a nightmare trying to include an assembly routine in an mbed-os (5) project. I then want to export the project to Keil uVision v5.29 and compile it there so that students can then debug it using the Keil debugger to see the code being executed etc.

In the past I had no problems with exporting projects from mbed to uVision4 but now the option to export has changed to uvision5-armc6 just doesn’t seem to download projects that I can add an assembly file to and compile sucessfully.

Ultimately I want an mbed-os (5) running on an FRDM-K64F board with the application shield supporting the C12832 display with a link to an asm.s file where students can test out assembly instructions.

Has anyone got a C++ project working with their own assembly file to work within Keil v5.29 using the mbed-os (5) libraries and the V6 compiler? If so can you share it or share what options you set?