terom@53: /** Serial modes */
terom@52: static enum {
terom@52:     SERIAL_MODE_ASYNC   = 0b00,
terom@52: } serial_mode = SERIAL_MODE_ASYNC;
terom@52: 
terom@52: static enum {
terom@52:     SERIAL_BAUD_9600    = 103,
terom@52: } serial_baud = SERIAL_BAUD_9600;
terom@52: 
terom@52: static enum {
terom@52:     SERIAL_PARITY_N     = 0b00,
terom@52: } serial_parity = SERIAL_PARITY_N;
terom@52: 
terom@52: static enum {
terom@52:     SERIAL_STOPBITS_1   = 0b0,
terom@52: } serial_stopbits = SERIAL_STOPBITS_1;
terom@52: 
terom@52: static enum {
terom@52:     SERIAL_CHARS_8      = 0b011,
terom@52: } serial_chars = SERIAL_CHARS_8;
terom@52: 
terom@53: /** Serial state */
terom@69: #define SERIAL_BUF 64
terom@69: 
terom@69: struct serial {
terom@69:     char buf[SERIAL_BUF];
terom@69:     byte in, out;
terom@69: } serial_rx;
terom@69: 
terom@53: char serial_tx = 0;
terom@53: 
terom@53: void serial_enable (char rx, char tx);
terom@53: 
terom@52: /*
terom@52:  * Setup the UART for serial mode.
terom@52:  */
terom@52: void serial_init ()
terom@52: {
terom@52:     UCSR0A = (
terom@52:             // Double the USART Transmission Speed
terom@52:             (0b0 << U2X0)   // single speed
terom@52:             
terom@52:             // Multi-processor Communication Mode
terom@52:         |   (0b0 << MPCM0)  // off
terom@52:     );
terom@52:     UCSR0B = (
terom@52:             // Character Size
terom@52:             ((serial_chars >> 2) << UCSZ02) // standard character sizes
terom@52:     );
terom@52:     UCSR0C = (
terom@52:             // USART Mode Select
terom@52:             (serial_mode << UMSEL00) // async
terom@52: 
terom@52:             // Parity Mode
terom@52:         |   (serial_parity << UPM00)
terom@52:             
terom@52:             // Stop Bit Select
terom@52:         |   (serial_stopbits << USBS0)
terom@52: 
terom@52:             // Character Size
terom@52:         |   ((serial_chars & 0b11) << UCSZ00)
terom@52:         
terom@52:             // Clock Polarity
terom@52:         |   (0b0 << UCPOL0)
terom@52:     );
terom@52:     UBRR0 = serial_baud;
terom@53: 
terom@53:     // active RX, idle TX
terom@53:     serial_enable(1, 0);
terom@52: }
terom@52: 
terom@53: void serial_enable (char rx, char tx)
terom@52: {
terom@52:     UCSR0B = (
terom@53:             // RX Complete Interrupt Enable
terom@53:             (!!rx << RXCIE0)
terom@53: 
terom@53:             // USART Data Register Empty Interrupt Enable
terom@53:         |   (!!tx << UDRIE0)
terom@53: 
terom@52:             // Receiver Enable
terom@53:         |   (0b1 << RXEN0)  // enabled
terom@52: 
terom@52:             // Transmitter Enable
terom@52:         |   (0b1 << TXEN0)  // enabled
terom@52: 
terom@52:             // Character Size
terom@52:         |   ((serial_chars >> 2) << UCSZ02) // standard character sizes
terom@52:     );
terom@52: }
terom@52: 
terom@53: /*
terom@53:  * Read incoming into buffer.
terom@53:  */
terom@53: ISR(USART_RX_vect)
terom@53: {
terom@69:     serial_rx.buf[serial_rx.in++] = UDR0;
terom@69: 
terom@69:     if (serial_rx.in >= SERIAL_BUF)
terom@69:         serial_rx.in = 0;
terom@53: }
terom@53: 
terom@53: /*
terom@53:  * Write outgoing buffer.
terom@53:  */
terom@53: ISR(USART_UDRE_vect)
terom@53: {
terom@53:     UDR0 = serial_tx;
terom@53: 
terom@53:     // tx buffer consumed
terom@53:     serial_tx = 0;
terom@53: 
terom@53:     // idle tx
terom@53:     serial_enable(1, 0);
terom@53: }
terom@53: 
terom@52: char serial_read ()
terom@52: {
terom@69:     if (serial_rx.out == serial_rx.in)
terom@69:         return 0;
terom@52: 
terom@69:     char rx = serial_rx.buf[serial_rx.out++];
terom@69: 
terom@69:     if (serial_rx.out >= SERIAL_BUF)
terom@69:         serial_rx.out = 0;
terom@53: 
terom@53:     return rx;
terom@52: }
terom@52: 
terom@52: void serial_write (char c)
terom@52: {
terom@53:     // XXX: atomic?
terom@53:     if (tbi(&UCSR0A, UDRE0)) {
terom@53:         // direct
terom@53:         UDR0 = c;
terom@53:     } else {
terom@53:         // buffered
terom@53:         serial_tx = c;
terom@53:         serial_enable(1, 1);
terom@53:     }
terom@52: }