WARP Project Forums - Wireless Open-Access Research Platform

The easiest place to start would be the "NO MAC" reference design.  This is the minimal implementation of a lower-level MAC.  Hopefully, this will allow you to get a better sense of the interaction between various parts of the code.  The main thing to remember, is that the reference design extensively uses interrupts and callbacks in order to process events.  The interrupts allow the reference design to be more efficient when processing events; while the callbacks allow the reference design to be divided into MAC specific code and framework code that is common to all MACs.  Therefore, when you are looking at how functions are called, you have to also understand if that function is used as a callback and where the callback is invoked.

For example, in the case of the frame transmit of the DCF MAC, while the function itself is defined here, you can see that in main() the frame_transmit function is set as the "frame_tx_callback" for the wlan_mac_low_framework.  Then if we look at the wlan_mac_low_framework code in wlan_mac_low.c, you can see where the callback is invoked (i.e. as part of an IPC communication process between CPU High and CPU Low where CPU High tells CPU Low that a "TX_MPDU_READY").  If you study this case statement, you can see that the rate of the transmission used in the frame_tx_callback is set in the TX MPDU PHY parameters.  The TX MPDU comes from a packet buffer that serves as a data communication channel between CPU High and CPU Low, which is documented here.

Hopefully that helps get you started in understanding the reference design.  Just remember that the "Search" --> "File..." dialog in the SDK is very useful when looking for how functions are connected when you use "File name patterns" = "*.h, *.c".