avr_uart.h

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#ifndef AVR_UART_H
#define AVR_UART_H
 
/** \file */
 
#include <avr/io.h>
#include <stdint.h>
 
/** \brief Initialize USART
 *
 *  8 bit, 1 stop bit, no parity bit
 *
 *  \param uart_no: number of UART, like 0 or 1
 *
 *  \param ubrr: 12 bits of uint16_t: should be clock / 16 / baud - 1
 *
 *  \param rxIntEnable: 1 bit enable RX interrupt
 *
 */
#define UART_Init(uart_no, ubrr, rxIntEnable)                                  \
  _UART_Init(uart_no, ubrr, rxIntEnable)
 
/**
 * Second level of macro makes sure parameters are expanded before subbing into
 * string concatenation
 */
#define _UART_Init(uart_no, ubrr, rxIntEnable)                                 \
  UBRR##uart_no##H = (uint8_t)(ubrr >> 8) & 0xFF;                              \
  UBRR##uart_no##L = (uint8_t)(ubrr)&0xFF;                                     \
  UCSR##uart_no##A = 0;                                                        \
  UCSR##uart_no##C = (3 << UCSZ00);                                            \
  UCSR##uart_no##B = (1 << RXEN0) | (1 << TXEN0) | (rxIntEnable << RXCIE0);
 
// Enable/disable USART_UDRE_vect interrupt that triggers when USART (transmit)
// data register is empty i.e. ready for more data
#define USART_enable_udre_interrupt(uart_no)                                   \
  UCSR##uart_no##B |= (1 << UDRIE##uart_no)
#define USART_disable_udre_interrupt(uart_no)                                  \
  UCSR##uart_no##B &= ~(1 << UDRIE##uart_no)
 
/** \brief Define the ISR for a USART to push rx bytes to a circular buffer
 *
 * Defines the interrupt handler for the given USART. The interrupt handler
 * will push all rx bytes to the back of the circular buffer the user provides.
 *
 * ## Notes
 *
 * **DON'T USE A SEMICOLON AFTER THIS MACRO.**
 *
 * **Use atomic operations to remove data from the front of the circular
 * buffer** like `CM_ATOMIC_BLOCK() {}`
 *
 * **Make sure to setup the USART with rx interrupt enabled:**
 * `USART0_Init(<ubrr>,1)`
 *
 * **Make sure to turn enable the global interrupt flag:** `sei();`
 *
 * ## Parameters
 *
 * isr_name: USART_RX_vect for 328
 *
 * data_register: UDR0 for 328
 *
 * circular_buffer: a pointer to a circular_buffer_uint8 that you want received
 * bytes pushed_back on.
 *
 */
#define def_usart_isr_push_rx_to_circ_buf(isr_name, data_register,             \
                                          circular_buffer)                     \
  ISR(USART_RX_vect) { circular_buffer_push_back_uint8(circular_buffer, UDR0); }
 
#endif