uart.c

Go to the documentation of this file.

#include "sysdef.h"            // #define SERIAL_OUT_ON, #define HOST_BAUD_RATE
#if defined(SERIAL_OUT_ON) | defined(__DOXYGEN__)
    #include <avr/io.h>        // UCSR0A, UDRE0, U2X0, UCSR0B, TXEN0, UCSR0C,
                               // UCSZ00, UCSZ01, UBRR0H, UBRR0L, UDR0
    #include <stddef.h>        // NULL
    #include <stdio.h>         // struct FILE, stdout,
                               // #define FDEV_SETUP_STREAM(),
                               // #define _FDEV_SETUP_WRITE
#endif
#include "uart.h"

#if defined(SERIAL_OUT_ON) | defined(__DOXYGEN__)

    // define registers used by MCU used
    #if defined(__AVR_ATmega48__)   | defined(__AVR_ATmega48A__)   \
      | defined(__AVR_ATmega48P__)  | defined(__AVR_ATmega48PA__)  \
      | defined(__AVR_ATmega88__)   | defined(__AVR_ATmega88A__)   \
      | defined(__AVR_ATmega88P__)  | defined(__AVR_ATmega88AP__)  \
      | defined(__AVR_ATmega168__)  | defined(__AVR_ATmega168A__)  \
      | defined(__AVR_ATmega168P__) | defined(__AVR_ATmega168PA__) \
      | defined(__AVR_ATmega328__)  | defined(__AVR_ATmega328P__)
        #define UART_CONTROL_A_REG      UCSR0A
        #define UART_DATA_REG_EMPTY_BIT UDRE0   // bit 5
        #define UART_DOUBLE_SPEED_BIT   U2X0    // bit 1
        #define UART_CONTROL_B_REG      UCSR0B
        #define UART_TX_ENABLE_BIT      TXEN0   // bit 3
        #define UART_CONTROL_C_REG      UCSR0C
                                        // 8 bit, no parity, 1 stop bit:
        #define UART_8N1_BITS           ((1<<UCSZ00) | (1<<UCSZ01)) // bits 5..1
        #define UART_BAUDRATE_HIGH_REG  UBRR0H
        #define UART_BAUDRATE_LOW_REG   UBRR0L
        #define UART_DATA_REG           UDR0
    #elif defined(__AVR_ATmega8__)
        #define UART_CONTROL_A_REG      UCSRA
        #define UART_DATA_REG_EMPTY_BIT UDRE    // bit 5
        #define UART_DOUBLE_SPEED_BIT   U2X     // bit 1
        #define UART_CONTROL_B_REG      UCSRB
        #define UART_TX_ENABLE_BIT      TXEN    // bit 3
        #define UART_CONTROL_C_REG      UCSRC
                                        // 8 bit, no parity, 1 stop bit:
        #define UART_8N1_BITS           ((1<<UCSZ0) | (1<<UCSZ1)) // bits 5..1
        #define UART_BAUDRATE_HIGH_REG  UBRRH
        #define UART_BAUDRATE_LOW_REG   UBRRL
        #define UART_DATA_REG           UDR
    #else
        #error "unknown MCU"
    #endif

    static int uart_putchar(char c, FILE *stream)
    {
        if (c == '\n') uart_putchar('\r', stream);

        // wait for empty transmit buffer
        while(!(UART_CONTROL_A_REG & (1<<UART_DATA_REG_EMPTY_BIT)));

        // put data into buffer, sends the data
        UART_DATA_REG = c;
        return 0;
    }

    static FILE uart_stdout
                     = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);

#endif

#if defined(SERIAL_OUT_ON)

    // for comment see uart.h
    void log_init(void)
    {
        // -- init uart
        #define BAUD HOST_BAUD_RATE // BAUD is input for setbaud.h
        #include <util/setbaud.h>   // #define UBRRH_VALUE, UBRRL_VALUE, USE_2X
        UART_BAUDRATE_HIGH_REG = UBRRH_VALUE;
        UART_BAUDRATE_LOW_REG  = UBRRL_VALUE;
        #if USE_2X
            // double transmission speed
            UART_CONTROL_A_REG |= (1<<UART_DOUBLE_SPEED_BIT);
        #else
            UART_CONTROL_A_REG &= ~(1<<UART_DOUBLE_SPEED_BIT);
        #endif
        UART_CONTROL_C_REG = UART_8N1_BITS;             // set line mode
        UART_CONTROL_B_REG = (1<<UART_TX_ENABLE_BIT);   // enable transmitter

        // -- redirect stdout to uart
        stdout = &uart_stdout;
    }

#endif