Move uart stuff to external file. Working digital_read() function.

digital_read/Makefile

@@ -51,7 +51,7 @@ FORMAT = ihex
 TARGET = main
 
 # List C source files here. (C dependencies are automatically generated.) 
-SRC = $(TARGET).c
+SRC = $(TARGET).c uart_async.c
 
 # List Assembler source files here.
 #     Make them always end in a capital .S.  Files ending in a lowercase .s

digital_read/main.c

@@ -14,6 +14,11 @@
  *
  */
 
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
 #include <stdlib.h>
 #include <avr/io.h>
 #include <stdio.h>
@@ -22,80 +27,88 @@
 #include <avr/sfr_defs.h>
 
 #include "main.h"
-
+#include "uart.h"
-#ifndef F_CPU
-#define F_CPU 16000000UL
-#endif
-
-#define BAUD 9600
-#include <util/setbaud.h>
-
-volatile uint8_t interrupts;
-char buffer[1];
-
-static void uart_init(void) {
-    UBRR0H = UBRRH_VALUE;
-    UBRR0L = UBRRL_VALUE;
-
-    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00);
-    UCSR0B = _BV(RXEN0) | _BV(TXEN0);
-}
-
-static int uart_putchar(char c, FILE *stream) {
-    loop_until_bit_is_set(UCSR0A, UDRE0);
-    UDR0 = c;
-    return 0;
-}
-
-static int uart_getchar(FILE *stream) {
-    loop_until_bit_is_set(UCSR0A, RXC0);
-    return UDR0;
-}
-
-static int digital_read(sfr, bit) {
-    return bit_is_set(sft, bit) && 1;
-}
 
 void init(void) {
     
-    /* Make PORTD3..7 PORTD0..1 (Arduino digital 3..9) input by clearing bits in DDR */
+    /* Make PORTD2..7 PORTD0..1 (Arduino digital 3..11) input by clearing bits in DDR */
     DDRD &= ~(_BV(PORTD2) | _BV(PORTD3) | _BV(PORTD4) | _BV(PORTD5) | _BV(PORTD6) | _BV(PORTD7));
     DDRB &= ~(_BV(PORTB0) | _BV(PORTB1));
 
-    /* Disable pullups by clearing bits in PORT. Default state is now low. */
+    /* In input mode, when pull-up is enabled, default state of pin becomes ’1′. So even if */
-    /*
+    /* you don’t connect anything to pin and if you try to read it, it will read as 1. Now, */
-    PORTD &= ~(_BV(PORTD3) | _BV(PORTD4) | _BV(PORTD5) | _BV(PORTD6) | _BV(PORTD7));
+    /* when you externally drive that pin to zero(i.e. connect to ground / or pull-down),   */
-    PORTB &= ~(_BV(PORTB0) | _BV(PORTB1));
+    /* only then it will be read as 0. */
-    */
 
     /* Enable pullups by setting bits in PORT. Default state is now high. */
     PORTD |= (_BV(PORTD2) | _BV(PORTD3) | _BV(PORTD4) | _BV(PORTD5) | _BV(PORTD6) | _BV(PORTD7));
     PORTB |= (_BV(PORTB0) | _BV(PORTB1));
     
+    /* Disable pullups by clearing bits in PORT. Default state is now low. */
+    /*
+    PORTD &= ~(_BV(PORTD2) | _BV(PORTD3) | _BV(PORTD4) | _BV(PORTD5) | _BV(PORTD6) | _BV(PORTD7));
+    PORTB &= ~(_BV(PORTB0) | _BV(PORTB1));
+    */
+    
     /* Make PORTB5 (Arduino digital 13) an output by setting bit in DDR. */
     DDRB |= _BV(PORTB5);
     
 }
 
+int digital_read(int input_register, int pin) {
+    return bit_is_set(input_register, pin) != 0 ? 1 : 0;
+}
+
+/*
+void digital_write(int input_register, int pin) {
+    input_register |= _BV(pin);
+}
+*/
+
 int main(void) {    
     
     init();
     uart_init();
-    stdout = &output;
+    stdout = &uart_output;
-    stdin  = &input;
+    stdin  = &uart_input;
     
-    uint8_t value;
+    int  value;
-    char buffer[9];  
+    //char buffer[9];  
         
     while (1) {
         /* Blink led by toggling state of PORTB5 (Arduino digital 13). */
         PORTB ^= _BV(PORTB5);
 
-        /* Take 8bit value from PORTD3..7 PORTD0..1 */      
+        /*
-        value = (PIND >> 2) + (PINB << 6);
+        puts("PINB");
-
+        value = PINB;
         itoa(value, buffer, 2);
         puts(buffer);
+        */
+        
+        value = digital_read(PIND, PIND2);
+        printf("%d", value);
+
+        value = digital_read(PIND, PIND3);
+        printf("%d", value);
+
+        value = digital_read(PIND, PIND4);
+        printf("%d", value);
+
+        value = digital_read(PIND, PIND5);
+        printf("%d", value);
+
+        value = digital_read(PIND, PIND6);
+        printf("%d", value);
+
+        value = digital_read(PIND, PIND7);
+        printf("%d", value);
+        
+        value = digital_read(PINB, PINB0);
+        printf("%d", value);
+
+        value = digital_read(PINB, PINB1);
+        printf("%d\n", value);
         
         _delay_ms(500);    
     }

digital_read/main.h

@@ -1,8 +1,2 @@
-static int uart_putchar(char c, FILE *stream);
+static void uart_init(void);
-static int uart_getchar(FILE *stream);
-
-static void init_uart(void);
 static void init(void);
-
-static FILE output = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
-static FILE input = FDEV_SETUP_STREAM(NULL, uart_getchar, _FDEV_SETUP_READ );

digital_read/uart.h

@@ -0,0 +1,12 @@
+int uart_putchar(char c, FILE *stream);
+int uart_getchar(FILE *stream);
+
+void uart_init(void);
+
+struct rx_ring;
+struct tx_ring;
+
+/* http://www.ermicro.com/blog/?p=325 */
+
+FILE uart_output = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
+FILE uart_input = FDEV_SETUP_STREAM(NULL, uart_getchar, _FDEV_SETUP_READ);

digital_read/uart_async.c

@@ -0,0 +1,102 @@
+/* Based on Atmel Application Note AVR 306 */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <stdio.h>
+
+#ifndef BAUD
+#define BAUD 9600
+#endif
+#include <util/setbaud.h>
+
+#ifndef UART_RX_BUFFER_SIZE
+#define UART_RX_BUFFER_SIZE 64
+#endif
+
+#ifndef UART_TX_BUFFER_SIZE
+#define UART_TX_BUFFER_SIZE 64
+#endif
+
+struct tx_ring {
+    int buffer[UART_TX_BUFFER_SIZE];
+    int start;
+    int end;
+};
+
+struct rx_ring {
+    int buffer[UART_RX_BUFFER_SIZE];
+    int start;
+    int end;
+};
+
+static struct tx_ring tx_buffer;
+static struct rx_ring rx_buffer;
+
+/* http://www.cs.mun.ca/~rod/Winter2007/4723/notes/serial/serial.html */
+
+void uart_init(void) {
+    
+    tx_buffer.start = 0;
+    tx_buffer.end   = 0;
+
+    rx_buffer.start = 0;
+    rx_buffer.end   = 0;
+    
+    UBRR0H = UBRRH_VALUE;
+    UBRR0L = UBRRL_VALUE;
+
+    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */ 
+    UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */  
+    
+    sei();  
+}
+
+int uart_putchar(char c, FILE *stream) {
+    if (c == '\n') {
+        uart_putchar('\r', stream);
+    }
+    
+    int write_pointer = (tx_buffer.end + 1) % UART_TX_BUFFER_SIZE;
+    
+    if (write_pointer != tx_buffer.start){
+        tx_buffer.buffer[tx_buffer.end] = c;
+        tx_buffer.end = write_pointer;
+        
+        /* Data available. Enable the transmit interrupt for serial port 0. */
+        UCSR0B |= _BV(UDRIE0);  
+    }
+    
+    return 0;
+}
+
+int uart_getchar(FILE *stream) {
+    int read_pointer = (rx_buffer.start + 1) % UART_RX_BUFFER_SIZE;
+    
+    rx_buffer.start = read_pointer;
+    return rx_buffer.buffer[read_pointer];
+}
+
+ISR(USART_RX_vect) {
+    int write_pointer = (rx_buffer.end + 1) % UART_RX_BUFFER_SIZE;
+
+    /* Add next byte to ringbuffer if it has space available. */
+    if (write_pointer != rx_buffer.start){
+        rx_buffer.buffer[rx_buffer.end] = UDR0;
+        rx_buffer.end = write_pointer;
+    }
+}
+
+ISR(USART_UDRE_vect){
+    int read_pointer = (tx_buffer.start + 1) % UART_TX_BUFFER_SIZE;
+    
+    /* Transmit next byte if data available in ringbuffer. */
+    if (read_pointer != tx_buffer.end) {
+        UDR0 = tx_buffer.buffer[read_pointer];
+        tx_buffer.start = read_pointer;
+    } else {
+        /* Nothing to send. Disable the transmit interrupt for serial port 0. */
+        UCSR0B &= ~_BV(UDRIE0);
+    }
+}
+
+