UART Library#

This library provide a software defined UART (universal asynchronous receiver transmitter) allowing you to communicate with other UART enabled devices in your system. A UART is a single wire per direction communications interface allowing either half or full duplex communication. The components in this library are controlled via C and behave as a UART transmitter and/or receiver peripheral.

Various configuration options are available including baud rate (individually settable per direction), number of data bits (between 5 and 8), parity (EVEN, ODD or NONE) and number of stop bits (1 or 2). The UART does not support flow control signals. Only a single 1b IO port per UART direction is needed.

The Tx UART supports up to 1152000 baud unbuffered and 576000 baud buffered with a 75MHz logical core. The Rx UART supports up to 700000 baud unbuffered and 422400 baud buffered with a 75MHz logical core. Proportionally higher rates are achievable using a higher logical core MHz.

The UART receive supports standard error detection including START, PARITY and FRAMING errors. A callback mechanism is included to notify the user of these conditions.

The UART may be used in blocking mode, where the call to Tx/Rx does not return until the stop bit is complete. It may also be used in ISR/buffered mode where the UART Rx and/or Tx operates in background mode using a FIFO and callbacks to manage data-flow and error conditions. Cycles are stolen from the logical core which setup the interrupt. In ISR/buffered mode additional callbacks are supported indicating the UNDERRUN condition when the Tx buffer is empty and OVERRUN when the Rx buffer is full.

Table 16 UART data wires#


Transmit line controlled by UART Tx


Receive line controlled by UART Rx

All UART functions can be accessed via the uart.h header:

#include <uart.h>