In this reference design, the cradle can achieve the following function: detect the lid closing and send different commands to a pair of third-party earbuds. The left and right earbuds respond differently to the commands, and the cradle flashes the LED once if it receives the response from the right earbud, twice if it receives the response from the left earbud, and three times if it receives responses from both earbuds. When not in communication, the Pogo pin is set to 5 V and ready to charge the earbuds. Figure 5-1 shows a simple flowchart.

In this design, the main() function only contains the initialization, all the functions are achieved in the interrupts