Using printf() for sending strings to the USART

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Here is some example code to use printf() to send a string to the USART. This could easily be modified to send the string to other devices such as an LCD character display simply by modifying the put_char() function.

This was taken for the most part from the avr-libc manual. It is written for the mega16, but it should work for all AVRs with hardware USARTs with few or no changes.

#include 
#include 

static int put_char(char c, FILE *stream);

static FILE mystdout = FDEV_SETUP_STREAM(put_char, NULL, _FDEV_SETUP_WRITE);

void init_uart(void)
{
	UCSRB = (1<<RXEN) | (1<<TXEN); 
	UCSRC = (1<<URSEL) | (3<<UCSZ0); // 8 bit, 1 stop bit, no parity
	UBRRH = 0;
	UBRRL = 51; //9600 baud at 8 MHz
}

static int put_char(char c, FILE *stream)
{
	loop_until_bit_is_set(UCSRA, UDRE); // wait for UDR to be clear
	UDR = c;    //send the character
	return 0;
}

int main(void)
{
	init_uart();    // Initialize the uart
	stdout = &mystdout;    //set the output stream
	printf("Hello, world!\n");
	return 0;
}

Regards,
Steve A.

The Board helps those that help themselves.

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I always wondered how to do that. One example is worth a whole page of text explanation. My iccavr 6.30 version had 1510 bytes in the flash. Should I stick it in this thread? Or no iccavr users would see it here?

Imagecraft compiler user

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Some remarks: the initialization of UCSR[n]C can be avoided, as it
defaults to 8N1 framing anyway (which makes some sense). As the
handling of the various UCSR[n]C registers varies greatly between
devices (some of the AVRs share this register with the high part of
the baud rate divisor, others implement different options instead,
older AVRs don't have it at all), IMHO it's the most portable way
between different AVRs to not touch the register at all.

You are enabling the receiver even though you are not using it.

For 9600 Bd with only 1 MHz clock (both very common selections), the
U2X bit in UCSR[n]A should be set to yield an acceptable baud rate
error. That way, it's normally possible to run 9600 Bd text output on
the default 1 MHz RC oscillator as long as the operating environment
matches the calibration constraints (Vcc = 5 V, Tamb = 25 °C for most
AVRs).

Calculating the baud rate divisor is best done by the compiler.
Again, for the common case of CPU frequencies up to 20 MHz (currently
the highest possible speed grade anyway) and baud rates of at least
9600 Bd, UBRR[n]H doesn't need to be touched at all.

So my initialization would look like:

#define UART_BAUD 9600

void init_uart(void)
{
  UCSRB = (1<<TXEN);
#if F_CPU < 2000000UL && defined(U2X)
  UCSRA = _BV(U2X);             /* improve baud rate error by using 2x clk */
  UBRRL = (F_CPU / (8UL * UART_BAUD)) - 1;
#else
  UBRRL = (F_CPU / (16UL * UART_BAUD)) - 1;
#endif
}

If you want to make sure you're also covering abysmally slow baud
rates on the upper end of the CPU frequency range, you might have the
preprocessor check the (F_CPU / (16UL * UART_BAUD)) - 1 calculation,
and touch UBRR[n]H if it overflows 255. Again, older AVRs didn't have
UBRR[n]H at all.

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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Quote:
Calculating the baud rate divisor is best done by the compiler.

But the compiler is not always right! The calculation "(F_CPU / (16UL * UART_BAUD)) - 1" can be off by one. Take, for instance, 2400 baud and 16MHz. The answer that the equation gives you is 415. But the real answer is 415.67, which should be rounded to 416. Or with the UX2 bit set, 14400 baud and 16MHz, the answer is 137 when it should be 138. This produces an error of 1.5% instead of 0.1%. If you look at the baud rate tables in the datasheet, any value that has a negative error will be off by one with the above equation.

As for the UCSRC and UBRRH registers, I didn't originally have them either. I just added them so that the code would be a little clearer.

Regards,
Steve A.

The Board helps those that help themselves.

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Well, if you really think the rounding is important, add it to the
formula. Add half of the divisor to F_CPU before dividing:

#define USING_U2X (F_CPU < 2000000ul && defined(U2X))
#define BAUD_DIV (USING_U2X? 8: 16)
#define UBRRx (((F_CPU + (UART_BAUD) * (BAUD_DIV / 2)) / ((UART_BAUD) * BAUD_DIV) - 1))

Looks terrible, but will do the job.

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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Hi Steve - I had been wondering about how to do exactly this. With some minor modifications to your code (specifically changing register names for the ATMEGA168) I now have printf working perfectly. Thanks!

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I've modified the code in order to use printf for printing on the LCD display.

So on the above code I've changed the function put_char

static int put_char(char c, FILE *stream)
{
   //loop_until_bit_is_set(UCSRA, UDRE); // wait for UDR to be clear
   //UDR = c;    //send the character
   lcd_putc(c);
   return 0;
}

lcd_put is the function from lcd.c file:

/****************************************************************************
 Title	:   HD44780U LCD library
 Author:    Peter Fleury   http://jump.to/fleury
 File:	    $Id: lcd.c,v 1.13.2.5 2005/02/16 19:15:13 Peter Exp $
 Software:  AVR-GCC 3.3 
 Target:    any AVR device, memory mapped mode only for AT90S4414/8515/Mega

 DESCRIPTION
       Basic routines for interfacing a HD44780U-based text lcd display

       Originally based on Volker Oth's lcd library,
       changed lcd_init(), added additional constants for lcd_command(),
       added 4-bit I/O mode, improved and optimized code.

       Library can be operated in memory mapped mode (LCD_IO_MODE=0) or in 
       4-bit IO port mode (LCD_IO_MODE=1). 8-bit IO port mode not supported.
       
       Memory mapped mode compatible with Kanda STK200, but supports also
       generation of R/W signal through A8 address line.

 USAGE
       See the C include lcd.h file for a description of each function
       
*****************************************************************************/
#include 
#include 
#include 
#include "lcd.h"



/* 
** constants/macros 
*/
#define DDR(x) (*(&x - 1))      /* address of data direction register of port x */
//#if defined(__AVR_ATmega64__) || defined(__AVR_ATmega128__)
    /* on ATmega64/128 PINF is on port 0x00 and not 0x60 */
    #define PIN(x) ( &PORTF==&(x) ? _SFR_IO8(0x00) : (*(&x - 2)) )
//#else
//	#define PIN(x) (*(&x - 2))    /* address of input register of port x          */
//#endif


#if LCD_IO_MODE
#define lcd_e_delay()   __asm__ __volatile__( "rjmp 1f\n 1:" );
#define lcd_e_high()    LCD_E_PORT  |=  _BV(LCD_E_PIN);
#define lcd_e_low()     LCD_E_PORT  &= ~_BV(LCD_E_PIN);
#define lcd_e_toggle()  toggle_e()
#define lcd_rw_high()   LCD_RW_PORT |=  _BV(LCD_RW_PIN)
#define lcd_rw_low()    LCD_RW_PORT &= ~_BV(LCD_RW_PIN)
#define lcd_rs_high()   LCD_RS_PORT |=  _BV(LCD_RS_PIN)
#define lcd_rs_low()    LCD_RS_PORT &= ~_BV(LCD_RS_PIN)
#endif

#if LCD_IO_MODE
#if LCD_LINES==1
#define LCD_FUNCTION_DEFAULT    LCD_FUNCTION_4BIT_1LINE 
#else
#define LCD_FUNCTION_DEFAULT    LCD_FUNCTION_4BIT_2LINES 
#endif
#else
#if LCD_LINES==1
#define LCD_FUNCTION_DEFAULT    LCD_FUNCTION_8BIT_1LINE
#else
#define LCD_FUNCTION_DEFAULT    LCD_FUNCTION_8BIT_2LINES
#endif
#endif


/* 
** function prototypes 
*/
#if LCD_IO_MODE
static void toggle_e(void);
#endif

/*
** local functions
*/



/*************************************************************************
 delay loop for small accurate delays: 16-bit counter, 4 cycles/loop
*************************************************************************/
static inline void _delayFourCycles(unsigned int __count)
{
    if ( __count == 0 )    
        __asm__ __volatile__( "rjmp 1f\n 1:" );    // 2 cycles
    else
        __asm__ __volatile__ (
    	    "1: sbiw %0,1" "\n\t"                  
    	    "brne 1b"                              // 4 cycles/loop
    	    : "=w" (__count)
    	    : "0" (__count)
    	   );
}


/************************************************************************* 
delay for a minimum of  microseconds
the number of loops is calculated at compile-time from MCU clock frequency
*************************************************************************/
#define delay(us)  _delayFourCycles( ( ( 1*(XTAL/4000) )*us)/1000 )


#if LCD_IO_MODE
/* toggle Enable Pin to initiate write */
static void toggle_e(void)
{
    lcd_e_high();
    lcd_e_delay();
    lcd_e_low();
}
#endif


/*************************************************************************
Low-level function to write byte to LCD controller
Input:    data   byte to write to LCD
          rs     1: write data    
                 0: write instruction
Returns:  none
*************************************************************************/
#if LCD_IO_MODE
static void lcd_write(uint8_t data,uint8_t rs) 
{
    unsigned char dataBits ;


    if (rs) {   /* write data        (RS=1, RW=0) */
       lcd_rs_high();
    } else {    /* write instruction (RS=0, RW=0) */
       lcd_rs_low();
    }
    lcd_rw_low();

    if ( ( &LCD_DATA0_PORT == &LCD_DATA1_PORT) && ( &LCD_DATA1_PORT == &LCD_DATA2_PORT ) && ( &LCD_DATA2_PORT == &LCD_DATA3_PORT )
      && (LCD_DATA0_PIN == 0) && (LCD_DATA1_PIN == 1) && (LCD_DATA2_PIN == 2) && (LCD_DATA3_PIN == 3) )
    {
        /* configure data pins as output */
        DDR(LCD_DATA0_PORT) |= 0x0F;

        /* output high nibble first */
        dataBits = LCD_DATA0_PORT & 0xF0;
        LCD_DATA0_PORT = dataBits |((data>>4)&0x0F);
        lcd_e_toggle();

        /* output low nibble */
        LCD_DATA0_PORT = dataBits | (data&0x0F);
        lcd_e_toggle();

        /* all data pins high (inactive) */
        LCD_DATA0_PORT = dataBits | 0x0F;
    }
    else
    {
        /* configure data pins as output */
        DDR(LCD_DATA0_PORT) |= _BV(LCD_DATA0_PIN);
        DDR(LCD_DATA1_PORT) |= _BV(LCD_DATA1_PIN);
        DDR(LCD_DATA2_PORT) |= _BV(LCD_DATA2_PIN);
        DDR(LCD_DATA3_PORT) |= _BV(LCD_DATA3_PIN);
        
        /* output high nibble first */
        LCD_DATA3_PORT &= ~_BV(LCD_DATA3_PIN);
        LCD_DATA2_PORT &= ~_BV(LCD_DATA2_PIN);
        LCD_DATA1_PORT &= ~_BV(LCD_DATA1_PIN);
        LCD_DATA0_PORT &= ~_BV(LCD_DATA0_PIN);
    	if(data & 0x80) LCD_DATA3_PORT |= _BV(LCD_DATA3_PIN);
    	if(data & 0x40) LCD_DATA2_PORT |= _BV(LCD_DATA2_PIN);
    	if(data & 0x20) LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);
    	if(data & 0x10) LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);   
        lcd_e_toggle();
        
        /* output low nibble */
        LCD_DATA3_PORT &= ~_BV(LCD_DATA3_PIN);
        LCD_DATA2_PORT &= ~_BV(LCD_DATA2_PIN);
        LCD_DATA1_PORT &= ~_BV(LCD_DATA1_PIN);
        LCD_DATA0_PORT &= ~_BV(LCD_DATA0_PIN);
    	if(data & 0x08) LCD_DATA3_PORT |= _BV(LCD_DATA3_PIN);
    	if(data & 0x04) LCD_DATA2_PORT |= _BV(LCD_DATA2_PIN);
    	if(data & 0x02) LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);
    	if(data & 0x01) LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);
        lcd_e_toggle();        
        
        /* all data pins high (inactive) */
        LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);
        LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);
        LCD_DATA2_PORT |= _BV(LCD_DATA2_PIN);
        LCD_DATA3_PORT |= _BV(LCD_DATA3_PIN);
    }
}
#else
#define lcd_write(d,rs) if (rs) *(volatile uint8_t*)(LCD_IO_DATA) = d; else *(volatile uint8_t*)(LCD_IO_FUNCTION) = d;
/* rs==0 -> write instruction to LCD_IO_FUNCTION */
/* rs==1 -> write data to LCD_IO_DATA */
#endif


/*************************************************************************
Low-level function to read byte from LCD controller
Input:    rs     1: read data    
                 0: read busy flag / address counter
Returns:  byte read from LCD controller
*************************************************************************/
#if LCD_IO_MODE
static uint8_t lcd_read(uint8_t rs) 
{
    uint8_t data;
    
    
    if (rs)
        lcd_rs_high();                       /* RS=1: read data      */
    else
        lcd_rs_low();                        /* RS=0: read busy flag */
    lcd_rw_high();                           /* RW=1  read mode      */
    
    if ( ( &LCD_DATA0_PORT == &LCD_DATA1_PORT) && ( &LCD_DATA1_PORT == &LCD_DATA2_PORT ) && ( &LCD_DATA2_PORT == &LCD_DATA3_PORT )
      && ( LCD_DATA0_PIN == 0 )&& (LCD_DATA1_PIN == 1) && (LCD_DATA2_PIN == 2) && (LCD_DATA3_PIN == 3) )
    {
        DDR(LCD_DATA0_PORT) &= 0xF0;         /* configure data pins as input */
        
        lcd_e_high();
        lcd_e_delay();        
        data = PIN(LCD_DATA0_PORT) << 4;     /* read high nibble first */
        lcd_e_low();
        
        lcd_e_delay();                       /* Enable 500ns low       */
        
        lcd_e_high();
        lcd_e_delay();
        data |= PIN(LCD_DATA0_PORT)&0x0F;    /* read low nibble        */
        lcd_e_low();
    }
    else
    {
        /* configure data pins as input */
        DDR(LCD_DATA0_PORT) &= ~_BV(LCD_DATA0_PIN);
        DDR(LCD_DATA1_PORT) &= ~_BV(LCD_DATA1_PIN);
        DDR(LCD_DATA2_PORT) &= ~_BV(LCD_DATA2_PIN);
        DDR(LCD_DATA3_PORT) &= ~_BV(LCD_DATA3_PIN);
                
        /* read high nibble first */
        lcd_e_high();
        lcd_e_delay();        
        data = 0;
        if ( PIN(LCD_DATA0_PORT) & _BV(LCD_DATA0_PIN) ) data |= 0x10;
        if ( PIN(LCD_DATA1_PORT) & _BV(LCD_DATA1_PIN) ) data |= 0x20;
        if ( PIN(LCD_DATA2_PORT) & _BV(LCD_DATA2_PIN) ) data |= 0x40;
        if ( PIN(LCD_DATA3_PORT) & _BV(LCD_DATA3_PIN) ) data |= 0x80;
        lcd_e_low();

        lcd_e_delay();                       /* Enable 500ns low       */
    
        /* read low nibble */    
        lcd_e_high();
        lcd_e_delay();
        if ( PIN(LCD_DATA0_PORT) & _BV(LCD_DATA0_PIN) ) data |= 0x01;
        if ( PIN(LCD_DATA1_PORT) & _BV(LCD_DATA1_PIN) ) data |= 0x02;
        if ( PIN(LCD_DATA2_PORT) & _BV(LCD_DATA2_PIN) ) data |= 0x04;
        if ( PIN(LCD_DATA3_PORT) & _BV(LCD_DATA3_PIN) ) data |= 0x08;        
        lcd_e_low();
    }
    return data;
}
#else
#define lcd_read(rs) (rs) ? *(volatile uint8_t*)(LCD_IO_DATA+LCD_IO_READ) : *(volatile uint8_t*)(LCD_IO_FUNCTION+LCD_IO_READ)
/* rs==0 -> read instruction from LCD_IO_FUNCTION */
/* rs==1 -> read data from LCD_IO_DATA */
#endif


/*************************************************************************
loops while lcd is busy, returns address counter
*************************************************************************/
static uint8_t lcd_waitbusy(void)

{
    register uint8_t c;
    
    /* wait until busy flag is cleared */
    while ( (c=lcd_read(0)) & (1<<LCD_BUSY)) {}
    
    /* the address counter is updated 4us after the busy flag is cleared */
    delay(2);

    /* now read the address counter */
    return (lcd_read(0));  // return address counter
    
}/* lcd_waitbusy */


/*************************************************************************
Move cursor to the start of next line or to the first line if the cursor 
is already on the last line.
*************************************************************************/
static inline void lcd_newline(uint8_t pos)
{
    register uint8_t addressCounter;


#if LCD_LINES==1
    addressCounter = 0;
#endif
#if LCD_LINES==2
    if ( pos < (LCD_START_LINE2) )
        addressCounter = LCD_START_LINE2;
    else
        addressCounter = LCD_START_LINE1;
#endif
#if LCD_LINES==4
    if ( pos < LCD_START_LINE3 )
        addressCounter = LCD_START_LINE2;
    else if ( (pos >= LCD_START_LINE2) && (pos < LCD_START_LINE4) )
        addressCounter = LCD_START_LINE3;
    else if ( (pos >= LCD_START_LINE3) && (pos < LCD_START_LINE2) )
        addressCounter = LCD_START_LINE4;
    else 
        addressCounter = LCD_START_LINE1;
#endif
    lcd_command((1<<LCD_DDRAM)+addressCounter);

}/* lcd_newline */


/*
** PUBLIC FUNCTIONS 
*/

/*************************************************************************
Send LCD controller instruction command
Input:   instruction to send to LCD controller, see HD44780 data sheet
Returns: none
*************************************************************************/
void lcd_command(uint8_t cmd)
{
    lcd_waitbusy();
    lcd_write(cmd,0);
}


/*************************************************************************
Send data byte to LCD controller 
Input:   data to send to LCD controller, see HD44780 data sheet
Returns: none
*************************************************************************/
void lcd_data(uint8_t data)
{
    lcd_waitbusy();
    lcd_write(data,1);
}



/*************************************************************************
Set cursor to specified position
Input:    x  horizontal position  (0: left most position)
          y  vertical position    (0: first line)
Returns:  none
*************************************************************************/
void lcd_gotoxy(uint8_t x, uint8_t y)
{
#if LCD_LINES==1
    lcd_command((1<<LCD_DDRAM)+LCD_START_LINE1+x);
#endif
#if LCD_LINES==2
    if ( y==0 ) 
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE1+x);
    else
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE2+x);
#endif
#if LCD_LINES==4
    if ( y==0 )
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE1+x);
    else if ( y==1)
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE2+x);
    else if ( y==2)
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE3+x);
    else /* y==3 */
        lcd_command((1<<LCD_DDRAM)+LCD_START_LINE4+x);
#endif

}/* lcd_gotoxy */


/*************************************************************************
*************************************************************************/
int lcd_getxy(void)
{
    return lcd_waitbusy();
}


/*************************************************************************
Clear display and set cursor to home position
*************************************************************************/
void lcd_clrscr(void)
{
    lcd_command(1<<LCD_CLR);
}


/*************************************************************************
Set cursor to home position
*************************************************************************/
void lcd_home(void)
{
    lcd_command(1<<LCD_HOME);
}


/*************************************************************************
Display character at current cursor position 
Input:    character to be displayed                                       
Returns:  none
*************************************************************************/
void lcd_putc(char c)
{
    uint8_t pos;


    pos = lcd_waitbusy();   // read busy-flag and address counter
    if (c=='\n')
    {
        lcd_newline(pos);
    }
    else
    {
#if LCD_WRAP_LINES==1
#if LCD_LINES==1
        if ( pos == LCD_START_LINE1+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE1,0);
#elif LCD_LINES==2
        if ( pos == LCD_START_LINE1+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE2,0);    
        else if ( pos == LCD_START_LINE2+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE1,0);
#elif LCD_LINES==4
        if ( pos == LCD_START_LINE1+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE2,0);    
        else if ( pos == LCD_START_LINE2+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE3,0);
        else if ( pos == LCD_START_LINE3+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE4,0);
        else if ( pos == LCD_START_LINE4+LCD_DISP_LENGTH )
            lcd_write((1<<LCD_DDRAM)+LCD_START_LINE1,0);
#endif
        lcd_waitbusy();
#endif
        lcd_write(c, 1);
    }

}/* lcd_putc */


/*************************************************************************
Display string without auto linefeed 
Input:    string to be displayed
Returns:  none
*************************************************************************/
void lcd_puts(const char *s)
/* print string on lcd (no auto linefeed) */
{
    register char c;

    while ( (c = *s++) ) {
        lcd_putc(c);
    }

}/* lcd_puts */


/*************************************************************************
Display string from program memory without auto linefeed 
Input:     string from program memory be be displayed                                        
Returns:   none
*************************************************************************/
void lcd_puts_p(const char *progmem_s)
/* print string from program memory on lcd (no auto linefeed) */
{
    register char c;

    while ( (c = pgm_read_byte(progmem_s++)) ) {
        lcd_putc(c);
    }

}/* lcd_puts_p */


/*************************************************************************
Initialize display and select type of cursor 
Input:    dispAttr LCD_DISP_OFF            display off
                   LCD_DISP_ON             display on, cursor off
                   LCD_DISP_ON_CURSOR      display on, cursor on
                   LCD_DISP_CURSOR_BLINK   display on, cursor on flashing
Returns:  none
*************************************************************************/
void lcd_init(uint8_t dispAttr)
{
#if LCD_IO_MODE
    /*
     *  Initialize LCD to 4 bit I/O mode
     */
     
    if ( ( &LCD_DATA0_PORT == &LCD_DATA1_PORT) && ( &LCD_DATA1_PORT == &LCD_DATA2_PORT ) && ( &LCD_DATA2_PORT == &LCD_DATA3_PORT )
      && ( &LCD_RS_PORT == &LCD_DATA0_PORT) && ( &LCD_RW_PORT == &LCD_DATA0_PORT) && (&LCD_E_PORT == &LCD_DATA0_PORT)
      && (LCD_DATA0_PIN == 0 ) && (LCD_DATA1_PIN == 1) && (LCD_DATA2_PIN == 2) && (LCD_DATA3_PIN == 3) 
      && (LCD_RS_PIN == 4 ) && (LCD_RW_PIN == 5) && (LCD_E_PIN == 6 ) )
    {
        /* configure all port bits as output (all LCD lines on same port) */
        DDR(LCD_DATA0_PORT) |= 0x7F;
    }
    else if ( ( &LCD_DATA0_PORT == &LCD_DATA1_PORT) && ( &LCD_DATA1_PORT == &LCD_DATA2_PORT ) && ( &LCD_DATA2_PORT == &LCD_DATA3_PORT )
           && (LCD_DATA0_PIN == 0 ) && (LCD_DATA1_PIN == 1) && (LCD_DATA2_PIN == 2) && (LCD_DATA3_PIN == 3) )
    {
        /* configure all port bits as output (all LCD data lines on same port, but control lines on different ports) */
        DDR(LCD_DATA0_PORT) |= 0x0F;
        DDR(LCD_RS_PORT)    |= _BV(LCD_RS_PIN);
        DDR(LCD_RW_PORT)    |= _BV(LCD_RW_PIN);
        DDR(LCD_E_PORT)     |= _BV(LCD_E_PIN);
    }
    else
    {
        /* configure all port bits as output (LCD data and control lines on different ports */
        DDR(LCD_RS_PORT)    |= _BV(LCD_RS_PIN);
        DDR(LCD_RW_PORT)    |= _BV(LCD_RW_PIN);
        DDR(LCD_E_PORT)     |= _BV(LCD_E_PIN);
        DDR(LCD_DATA0_PORT) |= _BV(LCD_DATA0_PIN);
        DDR(LCD_DATA1_PORT) |= _BV(LCD_DATA1_PIN);
        DDR(LCD_DATA2_PORT) |= _BV(LCD_DATA2_PIN);
        DDR(LCD_DATA3_PORT) |= _BV(LCD_DATA3_PIN);
    }
    delay(16000);        /* wait 16ms or more after power-on       */
    
    /* initial write to lcd is 8bit */
    LCD_DATA1_PORT |= _BV(LCD_DATA1_PIN);  // _BV(LCD_FUNCTION)>>4;
    LCD_DATA0_PORT |= _BV(LCD_DATA0_PIN);  // _BV(LCD_FUNCTION_8BIT)>>4;
    lcd_e_toggle();
    delay(4992);         /* delay, busy flag can't be checked here */
   
    /* repeat last command */ 
    lcd_e_toggle();      
    delay(64);           /* delay, busy flag can't be checked here */
    
    /* repeat last command a third time */
    lcd_e_toggle();      
    delay(64);           /* delay, busy flag can't be checked here */

    /* now configure for 4bit mode */
    LCD_DATA0_PORT &= ~_BV(LCD_DATA0_PIN);   // LCD_FUNCTION_4BIT_1LINE>>4
    lcd_e_toggle();
    delay(64);           /* some displays need this additional delay */
    
    /* from now the LCD only accepts 4 bit I/O, we can use lcd_command() */    
#else
    /*
     * Initialize LCD to 8 bit memory mapped mode
     */
    
    /* enable external SRAM (memory mapped lcd) and one wait state */        
    MCUCR = _BV(SRE) | _BV(SRW);

    /* reset LCD */
    delay(16000);                           /* wait 16ms after power-on     */
    lcd_write(LCD_FUNCTION_8BIT_1LINE,0);   /* function set: 8bit interface */                   
    delay(4992);                            /* wait 5ms                     */
    lcd_write(LCD_FUNCTION_8BIT_1LINE,0);   /* function set: 8bit interface */                 
    delay(64);                              /* wait 64us                    */
    lcd_write(LCD_FUNCTION_8BIT_1LINE,0);   /* function set: 8bit interface */                
    delay(64);                              /* wait 64us                    */
#endif
    lcd_command(LCD_FUNCTION_DEFAULT);      /* function set: display lines  */
    lcd_command(LCD_DISP_OFF);              /* display off                  */
    lcd_clrscr();                           /* display clear                */ 
    lcd_command(LCD_MODE_DEFAULT);          /* set entry mode               */
    lcd_command(dispAttr);                  /* display/cursor control       */

}/* lcd_init */

and the lcd.h is:


#ifndef LCD_H
#define LCD_H
/*************************************************************************
 Title	:   C include file for the HD44780U LCD library (lcd.c)
 Author:    Peter Fleury   http://jump.to/fleury
 File:	    $Id: lcd.h,v 1.12.2.3 2004/12/09 21:05:17 peter Exp $
 Software:  AVR-GCC 3.3
 Hardware:  any AVR device, memory mapped mode only for AT90S4414/8515/Mega
***************************************************************************/

/**
 @defgroup pfleury_lcd LCD library
 @code #include  @endcode
 
 @brief Basic routines for interfacing a HD44780U-based text LCD display

 Originally based on Volker Oth's LCD library,
 changed lcd_init(), added additional constants for lcd_command(), 
 added 4-bit I/O mode, improved and optimized code.
       
 Library can be operated in memory mapped mode (LCD_IO_MODE=0) or in 
 4-bit IO port mode (LCD_IO_MODE=1). 8-bit IO port mode not supported.

 Memory mapped mode compatible with Kanda STK200, but supports also 
 generation of R/W signal through A8 address line.
       
 @author Peter Fleury pfleury@gmx.ch http://jump.to/fleury
 
 @see The chapter Interfacing a HD44780 Based LCD to an AVR
      on my home page.

*/

/*@{*/

#if (__GNUC__ * 100 + __GNUC_MINOR__) < 303
#error "This library requires AVR-GCC 3.3 or later, update to newer AVR-GCC compiler !"
#endif

#include 
#include 

/** 
 *  @name  Definitions for MCU Clock Frequency
 *  Adapt the MCU clock frequency in Hz to your target. 
 */
#define XTAL 8000000              /**< clock frequency in Hz, used to calculate delay timer */

/** 
 *  @name  Definitions for Display Size 
 *  Change these definitions to adapt setting to your display
 */
#define LCD_LINES           2     /**< number of visible lines of the display */
#define LCD_DISP_LENGTH    16     /**< visibles characters per line of the display */
#define LCD_LINE_LENGTH  0x40     /**< internal line length of the display    */
#define LCD_START_LINE1  0x00     /**< DDRAM address of first char of line 1 */
#define LCD_START_LINE2  0x40     /**< DDRAM address of first char of line 2 */
#define LCD_START_LINE3  0x14     /**< DDRAM address of first char of line 3 */
#define LCD_START_LINE4  0x54     /**< DDRAM address of first char of line 4 */
#define LCD_WRAP_LINES      0     /**< 0: no wrap, 1: wrap at end of visibile line */


#define LCD_IO_MODE      0         /**< 0: memory mapped mode, 1: IO port mode */
#if LCD_IO_MODE
/**
 *  @name Definitions for 4-bit IO mode
 *  Change LCD_PORT if you want to use a different port for the LCD pins.
 *
 *  The four LCD data lines and the three control lines RS, RW, E can be on the 
 *  same port or on different ports. 
 *  Change LCD_RS_PORT, LCD_RW_PORT, LCD_E_PORT if you want the control lines on
 *  different ports. 
 *
 *  Normally the four data lines should be mapped to bit 0..3 on one port, but it
 *  is possible to connect these data lines in different order or even on different
 *  ports by adapting the LCD_DATAx_PORT and LCD_DATAx_PIN definitions.
 *  
 */
#define LCD_PORT         PORTA        /**< port for the LCD lines   */
#define LCD_DATA0_PORT   LCD_PORT     /**< port for 4bit data bit 0 */
#define LCD_DATA1_PORT   LCD_PORT     /**< port for 4bit data bit 1 */
#define LCD_DATA2_PORT   LCD_PORT     /**< port for 4bit data bit 2 */
#define LCD_DATA3_PORT   LCD_PORT     /**< port for 4bit data bit 3 */
#define LCD_DATA0_PIN    0            /**< pin for 4bit data bit 0  */
#define LCD_DATA1_PIN    1            /**< pin for 4bit data bit 1  */
#define LCD_DATA2_PIN    2            /**< pin for 4bit data bit 2  */
#define LCD_DATA3_PIN    3            /**< pin for 4bit data bit 3  */
#define LCD_RS_PORT      PORTG //LCD_PORT     /**< port for RS line         */
#define LCD_RS_PIN       0            /**< pin  for RS line         */
#define LCD_RW_PORT      PORTG //LCD_PORT     /**< port for RW line         */
#define LCD_RW_PIN       5            /**< pin  for RW line         */
#define LCD_E_PORT       LCD_PORT     /**< port for Enable line     */
#define LCD_E_PIN        6            /**< pin  for Enable line     */

#elif defined(__AVR_AT90S4414__) || defined(__AVR_AT90S8515__) || defined(__AVR_ATmega64__) || \
      defined(__AVR_ATmega8515__)|| defined(__AVR_ATmega103__) || defined(__AVR_ATmega128__) || \
      defined(__AVR_ATmega161__) || defined(__AVR_ATmega162__)
/*
 *  memory mapped mode is only supported when the device has an external data memory interface
 */
#define LCD_IO_DATA      0xC000    /* A15=E=1, A14=RS=1                 */
#define LCD_IO_FUNCTION  0x8000    /* A15=E=1, A14=RS=0                 */
#define LCD_IO_READ      0x0100    /* A8 =R/W=1 (R/W: 1=Read, 0=Write   */
#else
#error "external data memory interface not available for this device, use 4-bit IO port mode"

#endif


/**
 *  @name Definitions for LCD command instructions
 *  The constants define the various LCD controller instructions which can be passed to the 
 *  function lcd_command(), see HD44780 data sheet for a complete description.
 */

/* instruction register bit positions, see HD44780U data sheet */
#define LCD_CLR               0      /* DB0: clear display                  */
#define LCD_HOME              1      /* DB1: return to home position        */
#define LCD_ENTRY_MODE        2      /* DB2: set entry mode                 */
#define LCD_ENTRY_INC         1      /*   DB1: 1=increment, 0=decrement     */
#define LCD_ENTRY_SHIFT       0      /*   DB2: 1=display shift on           */
#define LCD_ON                3      /* DB3: turn lcd/cursor on             */
#define LCD_ON_DISPLAY        2      /*   DB2: turn display on              */
#define LCD_ON_CURSOR         1      /*   DB1: turn cursor on               */
#define LCD_ON_BLINK          0      /*     DB0: blinking cursor ?          */
#define LCD_MOVE              4      /* DB4: move cursor/display            */
#define LCD_MOVE_DISP         3      /*   DB3: move display (0-> cursor) ?  */
#define LCD_MOVE_RIGHT        2      /*   DB2: move right (0-> left) ?      */
#define LCD_FUNCTION          5      /* DB5: function set                   */
#define LCD_FUNCTION_8BIT     4      /*   DB4: set 8BIT mode (0->4BIT mode) */
#define LCD_FUNCTION_2LINES   3      /*   DB3: two lines (0->one line)      */
#define LCD_FUNCTION_10DOTS   2      /*   DB2: 5x10 font (0->5x7 font)      */
#define LCD_CGRAM             6      /* DB6: set CG RAM address             */
#define LCD_DDRAM             7      /* DB7: set DD RAM address             */
#define LCD_BUSY              7      /* DB7: LCD is busy                    */

/* set entry mode: display shift on/off, dec/inc cursor move direction */
#define LCD_ENTRY_DEC            0x04   /* display shift off, dec cursor move dir */
#define LCD_ENTRY_DEC_SHIFT      0x05   /* display shift on,  dec cursor move dir */
#define LCD_ENTRY_INC_           0x06   /* display shift off, inc cursor move dir */
#define LCD_ENTRY_INC_SHIFT      0x07   /* display shift on,  inc cursor move dir */

/* display on/off, cursor on/off, blinking char at cursor position */
#define LCD_DISP_OFF             0x08   /* display off                            */
#define LCD_DISP_ON              0x0C   /* display on, cursor off                 */
#define LCD_DISP_ON_BLINK        0x0D   /* display on, cursor off, blink char     */
#define LCD_DISP_ON_CURSOR       0x0E   /* display on, cursor on                  */
#define LCD_DISP_ON_CURSOR_BLINK 0x0F   /* display on, cursor on, blink char      */

/* move cursor/shift display */
#define LCD_MOVE_CURSOR_LEFT     0x10   /* move cursor left  (decrement)          */
#define LCD_MOVE_CURSOR_RIGHT    0x14   /* move cursor right (increment)          */
#define LCD_MOVE_DISP_LEFT       0x18   /* shift display left                     */
#define LCD_MOVE_DISP_RIGHT      0x1C   /* shift display right                    */

/* function set: set interface data length and number of display lines */
#define LCD_FUNCTION_4BIT_1LINE  0x20   /* 4-bit interface, single line, 5x7 dots */
#define LCD_FUNCTION_4BIT_2LINES 0x28   /* 4-bit interface, dual line,   5x7 dots */
#define LCD_FUNCTION_8BIT_1LINE  0x30   /* 8-bit interface, single line, 5x7 dots */
#define LCD_FUNCTION_8BIT_2LINES 0x38   /* 8-bit interface, dual line,   5x7 dots */


#define LCD_MODE_DEFAULT     ((1<<LCD_ENTRY_MODE) | (1<<LCD_ENTRY_INC) )



/** 
 *  @name Functions
 */


/**
 @brief    Initialize display and select type of cursor
 @param    dispAttr \b LCD_DISP_OFF display off\n
                    \b LCD_DISP_ON display on, cursor off\n
                    \b LCD_DISP_ON_CURSOR display on, cursor on\n
                    \b LCD_DISP_ON_CURSOR_BLINK display on, cursor on flashing             
 @return  none
*/
extern void lcd_init(uint8_t dispAttr);


/**
 @brief    Clear display and set cursor to home position
 @param    void                                        
 @return   none
*/
extern void lcd_clrscr(void);


/**
 @brief    Set cursor to home position
 @param    void                                        
 @return   none
*/
extern void lcd_home(void);


/**
 @brief    Set cursor to specified position
 
 @param    x horizontal position\n (0: left most position)
 @param    y vertical position\n   (0: first line)
 @return   none
*/
extern void lcd_gotoxy(uint8_t x, uint8_t y);


/**
 @brief    Display character at current cursor position
 @param    c character to be displayed                                       
 @return   none
*/
extern void lcd_putc(char c);


/**
 @brief    Display string without auto linefeed
 @param    s string to be displayed                                        
 @return   none
*/
extern void lcd_puts(const char *s);


/**
 @brief    Display string from program memory without auto linefeed
 @param    s string from program memory be be displayed                                        
 @return   none
 @see      lcd_puts_P
*/
extern void lcd_puts_p(const char *progmem_s);


/**
 @brief    Send LCD controller instruction command
 @param    cmd instruction to send to LCD controller, see HD44780 data sheet
 @return   none
*/
extern void lcd_command(uint8_t cmd);


/**
 @brief    Send data byte to LCD controller 
 
 Similar to lcd_putc(), but without interpreting LF
 @param    data byte to send to LCD controller, see HD44780 data sheet
 @return   none
*/
extern void lcd_data(uint8_t data);


/**
 @brief macros for automatically storing string constant in program memory
*/
#define lcd_puts_P(__s)         lcd_puts_p(PSTR(__s))

/*@}*/
#endif //LCD_H

I hope this post is not to long.

so in the main.c file I can call now :

printf("%c", data[j]); ro display the data on direct to LCD.

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Quote:
I've modified the code in order to use printf for printing on the LCD display.

This is one of the main advantages of using printf. It makes it very easy to redirect the output to whatever device you want. The same type of change can send the output to SPI, TWI, or any other byte-wise output.

Regards,
Steve A.

The Board helps those that help themselves.

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Koshchi wrote:
Quote:
I've modified the code in order to use printf for printing on the LCD display.

This is one of the main advantages of using printf. It makes it very easy to redirect the output to whatever device you want. The same type of change can send the output to SPI, TWI, or any other byte-wise output.

It is true and thanks for sharing with us your code

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Quote:
thanks for sharing with us your code

Your welcome, but most of it is not my code. The majority is from the avr-libc manual.

Regards,
Steve A.

The Board helps those that help themselves.

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So if I wrote my put_char function so it used a parameter 0-3 to represent each of the ports on a ATMega640.

Would I still be able to use the streams?

static int put_char(char c, char port, FILE *stream)
{
.
.
.
}

Jeff

Jeff Dombach, JLD Systems
"We do the stuff behind the buttons!"
Your source for embedded solutions with a 100% Guarantee.
http://www.jldsystems.com
Phone 717.892.1100

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> So if I wrote my put_char function so it used a parameter 0-3 to
> represent each of the ports on a ATMega640.

> Would I still be able to use the streams?

> static int put_char(char c, char port, FILE *stream)

No, you cannot modify the internal calling interface, as all stdio
functions on top (like vfprintf()) would have to know about the
parameter sequence: they are (eventually) calling your backend
function.

However, this your desire is exactly the reason why avr-libc 1.4
extended the callback interface to pass the pointer to the original
stream down to the backend function. You can now attach "user data"
to the stream (which are opaque to the library itself).

Example (compiles fine, but untested):


#include 
#include 
#include 

static int uart_putchar(char c, FILE *stream);
static void init_uarts(void);

struct uart_port {
  volatile uint8_t *udr;
  volatile uint8_t *ucsra;
};

static FILE uart0 = FDEV_SETUP_STREAM(uart_putchar, NULL,
                                      _FDEV_SETUP_WRITE);
struct uart_port uart_port0 = { .udr = &UDR0, .ucsra = &UCSR0A };

static FILE uart1 = FDEV_SETUP_STREAM(uart_putchar, NULL,
                                      _FDEV_SETUP_WRITE);
struct uart_port uart_port1 = { .udr = &UDR1, .ucsra = &UCSR1A };

static FILE uart2 = FDEV_SETUP_STREAM(uart_putchar, NULL,
                                      _FDEV_SETUP_WRITE);
struct uart_port uart_port2 = { .udr = &UDR2, .ucsra = &UCSR2A };

static FILE uart3 = FDEV_SETUP_STREAM(uart_putchar, NULL,
                                      _FDEV_SETUP_WRITE);
struct uart_port uart_port3 = { .udr = &UDR3, .ucsra = &UCSR3A };

/* simplify: all USARTs use the same bit numbers */
#define UDRE UDRE0

static int
uart_putchar(char c, FILE *stream)
{
  struct uart_port *p = (struct uart_port *)fdev_get_udata(stream);

  if (c == '\n')
    uart_putchar('\r', stream);
  while (!(*p->ucsra & _BV(UDRE)))
    /* wait */;
  *p->udr = c;
  return 0;
}

static void
init_uarts(void)
{
  UCSR0A = _BV(U2X0);
  UCSR0B = _BV(TXEN0);
  UBRR0 = 12; /* 9600 Bd @ 1 MHz, U2X set */
  fdev_set_udata(&uart0, (void *)&uart_port0);

  UCSR1A = _BV(U2X1);
  UCSR1B = _BV(TXEN1);
  UBRR1 = 12; /* 9600 Bd @ 1 MHz, U2X set */
  fdev_set_udata(&uart1, (void *)&uart_port1);

  UCSR2A = _BV(U2X2);
  UCSR2B = _BV(TXEN2);
  UBRR2 = 12; /* 9600 Bd @ 1 MHz, U2X set */
  fdev_set_udata(&uart2, (void *)&uart_port2);

  UCSR3A = _BV(U2X3);
  UCSR3B = _BV(TXEN3);
  UBRR3 = 12; /* 9600 Bd @ 1 MHz, U2X set */
  fdev_set_udata(&uart3, (void *)&uart_port3);
}

int
main(void)
{
  init_uarts();

  fprintf(&uart0, "Hello, UART0\n");
  fprintf(&uart1, "Hello, UART1\n");
  fprintf(&uart2, "Hello, UART2\n");
  fprintf(&uart3, "Hello, UART3\n");

  return 0;
}

Let me know if that works. Perhaps I'm going to polish it up as an official
avr-libc example, to illustrate the concept of fdev_set_udata() and
fdev_get_udata().

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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That seems like what I want to accomplish. I will experiment with also how to process commands from all four serial ports thru the same parser. I have never used the streams, I have just put the characters into interrupt driven circular FIFO buffers and then wrote my own input/output routines to eliminate the printf overhead.

Although, with further reflection, I envision code like this:

for (uart_port=0; uart_port++; uart_port>=UART_PORT_MAX){
     if (uart_cmdchk(uart_port)) {
        parsecmd(uart_port);        
        uart_puts_p(uart_port,PSTR("<\n\r"));
     }
}

This would make it easy to maintain and support 1,2 or 4 ports depending on the micro.

Such that your example in main might be similar to:

main(void)
{
  for (uart_port=0; uart_port++; uart_port>=UART_PORT_MAX) {
      init_uart(uart_port);
      fprintf(uart_port, "Hello, UART\i\n", uart_port);
  }
  return 0;
} 

Jeff

Edit: additional ideas and internal human :) compiler errors.

Jeff Dombach, JLD Systems
"We do the stuff behind the buttons!"
Your source for embedded solutions with a 100% Guarantee.
http://www.jldsystems.com
Phone 717.892.1100

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Hello,

I am using stk500 , jtagice mkII and avr mega16. I am using RS232 for programming my avr. Let me know one thing can I use my this programming port for transferring my printf statements.

Thanks,
Anmol Kumar

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1. Program your mega16 with the STK500.

2. transfer your RS232 cable from the programming DB9 socket to the user DB9 socket. (you should have jumpered the "RS232 SPARE" header to PORTD.0 and PORTD.1)

3. Use your favourite terminal program with the relevant COM port for your cable. "Connect" to your AVR.

4. Before programming with STK500 again, "Disconnect" your terminal program. Change your DB9 sockets again for the STK500.

5. Life is easier with two RS232 cables.

6. Life is probably even easier if you use your JTAG for programming and debugging. Then you do not need to use the STK500 software at all. Just use the STK500 hardware. You only need to change cables if you want to hi-voltage program or change the VTG or on-board clock.

David.

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Thanks David,

Thats right even I am doing the same , actually my question was that I have to inteact with modem through AT commands and for the same Mine RS232 spare is already used by the modem , so, I was interested in knowing can I use that programming port (RS232 CTRL of STK500 or JTAGICE mkII) for transferring my printf statements .

actually during debugging I have to use RS232 used for programming originally ie. why I was interesting in knowing can I transfer those printf to this port.

Thanks,
Anmol Kumar

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The answer is no. The STK500 RS232 buffers are hardwired to the STK500 controller AVR.

I am sure that you could hack them trough and replace with jumpers. Your mega16 only has a single UART so you would need a software UART.

If you are only sending printf debug messages, then a software UART with a simple transistor level translator will drive an RS232 cable. If you do the inversion in software, you will probably find that a PC will read your 0..5V levels ok instead of the -12..+12V levels.

David.

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Ok David,

first thanks for reply and I somewhat got your point ie. why max202 is used near RS232 spare in stk500.

Thanks,
Anmol Kumar