Architecture of Bluetooth Peripheral Sample

Question

Hello guys, 
 
 I'm trying to clearly understand the Bluetooth Peripheral Sample github.com/.../peripheral_uart and how it exactly works.. so i'm curious if there are some software diagrams or architectures that describes this code ? and also i'm curious about applying some unit tests on some functions, so any example for for that ? looking forward for you help ! 
 Thanks in advance ! 
 best regards

Priyanka · Answer

This is an expected behaviour, and is part of the UART asynchronous API's functionality. When you call uart_rx_buf_rsp(uart, buf->data, sizeof(buf->data)); , you're providing a second buffer for the UART driver to use, once the first buffer is filled. 
 The UART_RX_BUF_RELEASED event is generated when the current buffer is no longer used by the driver. This event can occur multiple times for the same buffer, depending on the implementation. The buffer may be released when it is completely or partially filled. 
 In your logs, the first UART_RX_BUF_RELEASED event is triggered when the first buffer (buf=0x2000b180) is filled and no longer used by the driver. The second UART_RX_BUF_RELEASED event is triggered when the second buffer (buf=0x2000b198) is no longer used by the driver. The second buffer is empty (len=0), which is why it's released immediately. Hope this clears your doubt. 
 
 Regards, 
 Priyanka