Serial port library

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.