This module allows to create and handle serial port instances. It is designed as a more sophisticated replacement for the app_uart module. The following are the advantages of this module over app_uart:

• API is more generic and robust: you can read or write any amount of bytes.
• Multi-instance capability.
• The module can work in three modes: POLLING, IRQ, and DMA.
• Calls can be asynchronous and synchronus (with timeouts).
• Independent RX/TX FIFOs with configurable sizes.
• Configurable RX/TX transfer buffers (smallest transfer slice).
• Event handler (not mandatory).
• Sleep handler (not mandatory).

You can initialize this module in one of the three available modes:

• NRF_SERIAL_MODE_POLLING - Simple polling operation without any interrupts.
  • Functional timeouts.
  • Only 6-byte size hardware FIFO.
• NRF_SERIAL_MODE_IRQ - Interrupt mode.
  • Software FIFOs with configured size.
  • User-defined transfer slice size.
  • Funtional timeouts.
  • User-defined event and sleep handlers.
• NRF_SERIAL_MODE_DMA - Same functionality as in IRQ mode but uses EasyDMA.

The following code snippet shows how to create a configuration structure for each of these modes:

        
         NRF_SERIAL_CONFIG_DEF
        
        (serial_config_polling,
        
         NRF_SERIAL_MODE_POLLING
        
        ,
       

        NULL, NULL, NULL, NULL);
       

        
         NRF_SERIAL_CONFIG_DEF
        
        (serial_config_irq,
        
         NRF_SERIAL_MODE_IRQ
        
        ,
       

        &queues, &buffers, NULL, NULL);
       

        
         NRF_SERIAL_CONFIG_DEF
        
        (serial_config_dma,
        
         NRF_SERIAL_MODE_DMA
        
        ,
       

        &queues, &buffers, NULL, NULL);
       

Such configuration structure can be passed directly to the nrf_serial_init method. The table below shows the configuration dependencies:

• R - Required
• O - Optional
• U - Unused

Mode/Configuration	QUEUES	BUFFERS	EVENT_HANDLER	SLEEP_HANDLER
NRF_SERIAL_MODE_POLLING	U	U	U	U
NRF_SERIAL_MODE_IRQ	R	R	O	O
NRF_SERIAL_MODE_DMA	R	R	O	O

In Interrupt and DMA modes, you must create the RX/TX queues. The following code snippet shows how to create an instance of the RX/TX queue:

        
         #define SERIAL_FIFO_TX_SIZE 32
        
       

        
        
        
         #define SERIAL_FIFO_RX_SIZE 32
        
       

        
        
       

        
         NRF_SERIAL_QUEUES_DEF
        
        (serial_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);
       

Interrupt and DMA modes require a definition of the transfer buffers. They are the smallest slices of data that can be transfered in a single UART driver driver request. The following code snippet shows how to declare transfer buffers:

        
         #define SERIAL_BUFF_TX_SIZE 1
        
       

        
        
        
         #define SERIAL_BUFF_RX_SIZE 1
        
       

        
        
       

        
         NRF_SERIAL_BUFFERS_DEF
        
        (serial_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);
       

For API documentation of this library, refer to Serial port abstraction layer .

For a usage example, refer to Serial Port Library Example .