tmk_core/common/uart.c


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generated by cgit v1.2.3 (git 2.25.1) at 2025-11-14 18:30:22 +0000
 

">) ; // wait until space in buffer
	//cli();
	tx_buffer[i] = c;
	tx_buffer_head = i;
	UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0) | (1<<UDRIE0);
	//sei();
}

// Receive a byte
uint8_t uart_getchar(void)
{
        uint8_t c, i;

	while (rx_buffer_head == rx_buffer_tail) ; // wait for character
        i = rx_buffer_tail + 1;
        if (i >= RX_BUFFER_SIZE) i = 0;
        c = rx_buffer[i];
        rx_buffer_tail = i;
        return c;
}

// Return the number of bytes waiting in the receive buffer.
// Call this before uart_getchar() to check if it will need
// to wait for a byte to arrive.
uint8_t uart_available(void)
{
	uint8_t head, tail;

	head = rx_buffer_head;
	tail = rx_buffer_tail;
	if (head >= tail) return head - tail;
	return RX_BUFFER_SIZE + head - tail;
}

// Transmit Interrupt
ISR(USART_UDRE_vect)
{
	uint8_t i;

	if (tx_buffer_head == tx_buffer_tail) {
		// buffer is empty, disable transmit interrupt
		UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
	} else {
		i = tx_buffer_tail + 1;
		if (i >= TX_BUFFER_SIZE) i = 0;
		UDR0 = tx_buffer[i];
		tx_buffer_tail = i;
	}
}

// Receive Interrupt
ISR(USART_RX_vect)
{
	uint8_t c, i;

	c = UDR0;
	i = rx_buffer_head + 1;
	if (i >= RX_BUFFER_SIZE) i = 0;
	if (i != rx_buffer_tail) {
		rx_buffer[i] = c;
		rx_buffer_head = i;
	}
}