I am having trouble getting started... Not sure which files to look at !
The MCR20A transceiver is not supported by mbed. However, since it communicates to the MCU through SPI, it is possible to use it with mbed but you need to develop either the driver for the transceiver and the stack that you want to use. If you need to know how to build its drivers you should take a look into the MCR20A Reference Manual.
My advise is to take a look into the Freescale software built for the MCR20A for the Kinetis K64F and the Kinetis KL46Z where you will find not only the driver for the transceiver but stacks such SMAC and 802.15.4.
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