View topic - another strange problem with USART on atmega324

Search

another strange problem with USART on atmega324
Previous 1, 2, 3 Next All

AVR Freaks Forum Index » AVR (8-bit) Technical Forums » AVR forum

Author

Message

david.prentice

Posted: May 22, 2012 - 12:43 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

Well, I presume that you have a full CodeVision license. And the CodeWizard will create your interrupt code.

The mcu is used more efficiently with interrupts. It only executes instructions when required.
When you poll, you sit in a tight loop doing nothing apart from wait for a bit to be set.

Yes, the interrupt handling is more complex than polling. The CodeWizard writes it for you. Or you can use Atmel app notes. Or any code written for any cpu ever invented.

Before you can use any <stdio.h> functions, you must #include <stdio.h>

Code:

printf("Hello World\r\n");

while (1) {

    if (kbhit()) {

        putchar(getchar());

    }

}

David.

e0ne199

Posted: May 22, 2012 - 01:06 PM

Joined: Mar 27, 2010
Posts: 64

btw kbhit() that you mean is this :

Code:

//special macro

#define kbhit()    (rx_counter!= 0)

or this?

Code:

while (rx_counter0)     // anything there ?

   getchar();           // eat it.

thx 4 the previous help again Smile

bobgardner

Posted: May 22, 2012 - 01:32 PM

Joined: Sep 04, 2002
Posts: 21390
Location: Orlando Florida

You have used the word "packet" several times. I think we have some confusion of the use of this word. If you fill out your city and country in your profile, it will help the English speakers to recognize translation problems. I might respectfully suggest that you use a slightly more normal text style to improve the understandability of your messages. All thos lowercase abbreviations are hard to read. No need to save characters. You didn't respond to my question in a previous message. Some might regard this as an affront.

_________________
Imagecraft compiler user

e0ne199

Posted: May 22, 2012 - 01:51 PM

Joined: Mar 27, 2010
Posts: 64

bobgardner wrote:

ah sorry my bad, i'm still learning how to type in english well Sad

, and sometimes i get internet connection problems so the comment i submit is sometimes not displayed correctly (or even failed to submit) and it will take time to edit it again Sad

actually i did respond your comments on here:

Quote:

e0ne199 wrote:

the packet transfer and receive routines are all already included in the code, and the problems are when my mcus are trying to send an array of packets and receive it in master side ...the transmit code on the slave is like this :

Code:

interrupt [USART1_RXC] void usart1_rx_isr(void)

{

char status,data;

status=UCSR1A;

data=UDR1;

request_=data;

  if(request_==0x20) { putchar1(real_packet[1]);}

  if(request_==0x30) { putchar1(real_packet[2]);}

  if(request_==0x40) { putchar1(real_packet[3]);}      

  if(request_==0x60) { putchar1(real_packet2[0]);}

  if(request_==0x70) { putchar1(real_packet2[1]);}   

  if(request_==0x80) { putchar1(real_packet2[2]);}

  if(request_==0x90) { putchar1(real_packet2[3]);};

  ........

btw, when i try to compile my program (slave side) with codevision AVR by enabling 2 non-default warnings i have just set recently, after compilation i receive a message "possible loss of precision" on lines containing commands to send the array of packets...do you know how to solve this??
looks like the transmitted packet on slave side is distorted or something like that..

before that, thx for helping Smile

david.prentice

Posted: May 22, 2012 - 03:10 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

First off. How can anyone work with unformatted code?
Secondly. You have fiddled with the RX_USART ISR()

You appear to be peeking into a transitory value 'packet'
Instead you should read a whole sequence of bytes with getchar(). The whole point of buffered interrupts is that you will catch EVERY byte regardless of whether your robot is busy.

If you replace your 'packet' with getchar() you will process each byte in the correct order that it was received. (you can just do 4 getchar()s if you know there are 4 chars available otherwise you test rx_counter0)

David.;;

Code:

/*****************************************************

Project : automatic system for final project

Version : 1.0

Date    : 4/20/2012

Author  : E-1 

Company : E-1 Engineering Inc.

Comments: Simple implementation of my program model for my main system :)

Chip type               : ATmega324PA

Program type            : Application

AVR Core Clock frequency: 18.432000 MHz

Memory model            : Small

External RAM size       : 0

Data Stack size         : 512

*****************************************************/

#include <mega324a.h>

#include <delay.h>

#include <stdlib.h>

#include <stdio.h>

#ifndef RXB8

#define RXB8 1

#endif

#ifndef TXB8

#define TXB8 0

#endif

#ifndef UPE

#define UPE 2

#endif

#ifndef DOR

#define DOR 3

#endif

#ifndef FE

#define FE 4

#endif

#ifndef UDRE

#define UDRE 5

#endif

#ifndef RXC

#define RXC 7

#endif

#define FRAMING_ERROR (1<<FE)

#define PARITY_ERROR (1<<UPE)

#define DATA_OVERRUN (1<<DOR)

#define DATA_REGISTER_EMPTY (1<<UDRE)

#define RX_COMPLETE (1<<RXC)

//PWM

#define left_pwm OCR1BL

#define right_pwm OCR1AL

//global variables

char start, packet, val1, val2, val3, val4, val5, val6, val7, val8;

eeprom char id[3];

eeprom char location[4][3] = { {0, 0, 0},

{0, 0, 0},

{0, 0, 0},

{0, 0, 0}

};

int id_count = 0, count = 0, soft_left, soft_right, row = 0, line = 0;

// USART0 Receiver buffer

#define RX_BUFFER_SIZE0 32

char rx_buffer0[RX_BUFFER_SIZE0];

#if RX_BUFFER_SIZE0 <= 256

unsigned char rx_wr_index0, rx_rd_index0, rx_counter0;

#else

unsigned int rx_wr_index0, rx_rd_index0, rx_counter0;

#endif

// This flag is set on USART0 Receiver buffer overflow

bit rx_buffer_overflow0;

// USART0 Receiver interrupt service routine

interrupt [USART0_RXC] void usart0_rx_isr(void)

{

    char status, data;

    status = UCSR0A;

    data = UDR0;

    start = data;

    packet = data;

    if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN)) == 0) {

        rx_buffer0[rx_wr_index0++] = data;

#if RX_BUFFER_SIZE0 == 256

        // special case for receiver buffer size=256

        if (++rx_counter0 == 0) {

#else

        if (rx_wr_index0 == RX_BUFFER_SIZE0)

            rx_wr_index0 = 0;

        if (++rx_counter0 == RX_BUFFER_SIZE0) {

            rx_counter0 = 0;

#endif

            rx_buffer_overflow0 = 1;

        }

    }

}

#ifndef _DEBUG_TERMINAL_IO_

// Get a character from the USART0 Receiver buffer

#define _ALTERNATE_GETCHAR_

#pragma used+

char getchar(void)

{

    char data;

    while (rx_counter0 == 0);

    data = rx_buffer0[rx_rd_index0++];

#if RX_BUFFER_SIZE0 != 256

    if (rx_rd_index0 == RX_BUFFER_SIZE0)

        rx_rd_index0 = 0;

#endif

#asm("cli")

    --rx_counter0;

#asm("sei")

    return data;

}

#pragma used-

#endif

// Get a character from the USART1 Receiver

#pragma used+

char getchar1(void)

{

    char status, data;

    while (1) {

        while (((status = UCSR1A) & RX_COMPLETE) == 0);

        data = UDR1;

        if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN)) == 0)

            return data;

    }

}

#pragma used-

// Write a character to the USART1 Transmitter

#pragma used+

void putchar1(char c)

{

    while ((UCSR1A & DATA_REGISTER_EMPTY) == 0);

    UDR1 = c;

}

#pragma used-

inline void init()

{

    // Crystal Oscillator division factor: 1

#pragma optsize-

    CLKPR = 0x80;

    CLKPR = 0x00;

#ifdef _OPTIMIZE_SIZE_

#pragma optsize+

#endif

    // Port B initialization

    PORTB = 0x0F;

    DDRB = 0x00;

    //Port C initialization

    PORTC = 0x00;

    DDRC = 0xF0;

    //Port D initialization

    PORTD = 0x30;

    DDRD = 0x30;

    //for dynamixel

    PORTD.7 = 0;

    DDRD.7 = 1;

    //motor config

    //using OCR1AL & OCR1BL

    TCCR1A = 0xF1;

    TCCR1B = 0x02;

    TCNT1H = 0x00;

    TCNT1L = 0x00;

    ICR1H = 0x00;

    ICR1L = 0x00;

    OCR1AH = 0x00;

    OCR1AL = 0x00;

    OCR1BH = 0x00;

    OCR1BL = 0x00;

    // USART0 initialization

    // Communication Parameters: 8 Data, 1 Stop, No Parity

    // USART0 Receiver: On

    // USART0 Transmitter: On

    // USART0 Mode: Asynchronous

    // USART0 Baud Rate: 115200

    UCSR0A = 0x00;

    UCSR0B = 0x98;

    UCSR0C = 0x06;

    UBRR0H = 0x00;

    UBRR0L = 0x09;

    // USART1 initialization

    // Communication Parameters: 8 Data, 1 Stop, No Parity

    // USART1 Receiver: On

    // USART1 Transmitter: On

    // USART1 Mode: Asynchronous

    // USART1 Baud Rate: 115200

    UCSR1A = 0x00;

    UCSR1B = 0x18;

    UCSR1C = 0x06;

    UBRR1H = 0x00;

    UBRR1L = 0x09;

}

void packet_received()

{

    putchar(0x10);

    val1 = packet;

    putchar(0x20);

    val2 = packet;

    putchar(0x30);

    val3 = packet;

    putchar(0x40);

    val4 = packet;

}

//motor movement---------------------

void forward(int left, int right)

{

    left_pwm = left;

    right_pwm = right;

    PORTC.7 = 1;

    PORTC.6 = 0;

    PORTC.5 = 1;

    PORTC.4 = 0;

};

void backward(int left, int right)

{

    left_pwm = left;

    right_pwm = right;

    PORTC.7 = 0;

    PORTC.6 = 1;

    PORTC.5 = 0;

    PORTC.4 = 1;

};

void left(int left, int right)

{

    left_pwm = left;

    right_pwm = right;

    PORTC.7 = 1;

    PORTC.6 = 0;

    PORTC.5 = 0;

    PORTC.4 = 1;

};

void right(int left, int right)

{

    left_pwm = left;

    right_pwm = right;

    PORTC.7 = 0;

    PORTC.6 = 1;

    PORTC.5 = 1;

    PORTC.4 = 0;

};

void stop()

{

    PORTC.7 = 0;

    PORTC.6 = 0;

    PORTC.5 = 0;

    PORTC.4 = 0;

}

//-----------------------------------------

void arrange_position()

{

    while (val4 > 77) {

        putchar(0x40);

        val4 = packet;

        right(254, 250);

    };

    while (val4 > 50) {

        putchar(0x40);

        val4 = packet;

        left(254, 250);

    };

}

void dynamixel_push()

{

    putchar1(0xFF);

    putchar1(0xFF);

    putchar1(0x00);

    putchar1(0x07);

    putchar1(0x03);

    putchar1(0x1E);

    putchar1(0x10);

    putchar1(0x03);

    putchar1(0x00);

    putchar1(0x03);

    putchar1(0xC1);

    delay_ms(1000);

}

void dynamixel_pull()

{

    putchar1(0xFF);

    putchar1(0xFF);

    putchar1(0x00);

    putchar1(0x07);

    putchar1(0x03);

    putchar1(0x1E);

    putchar1(0xFE);

    putchar1(0x01);

    putchar1(0x00);

    putchar1(0x03);

    putchar1(0xD5);

    delay_ms(1000);

}

void preliminary()

{

    while (1) {

        if (start == 0xFF) {

            break;

        };

        if (packet == 0xAA) {

            id[id_count] = getchar();

            switch (id[id_count]) {

            case '9':

                location[1][1] = 1;

                break;

            case 'F':

                location[2][1] = 1;

                break;

            case '%':

                location[1][2] = 1;

                break;

                //some extra books

            case '3':

                location[2][2] = 1;

                break;

            case '<':

                location[1][1] = 1;

                break;

            default:

                break;

            };

            id_count++;

            if (id_count == 2) {

                id_count = 0;

            };

        };

        if (PINB.0 == 0) {

            putchar(0x01);

            delay_ms(250);

        };

        if (PINB.1 == 0) {

            putchar(0x02);

            delay_ms(250);

        };

        if (PINB.2 == 0) {

            putchar(0x03);

            delay_ms(250);

        };

        if (PINB.3 == 0) {

            putchar(0x04);

            delay_ms(250);

        };

    }

}

void transmit()

{

    PORTD.7 = 1;

    DDRD.7 = 1;

}

void receive()

{

    PORTD.7 = 0;

    DDRD.7 = 1;

}

void soft_start()

{

    soft_left = soft_right = 0;

    while (soft_left < 255 || soft_right < 255) {

        forward(soft_left, soft_right);

        soft_left++;

        soft_right++;

        delay_ms(5);

    }

}

void straight()

{

    while (1) {

        packet_received();

        forward(255, 255);

        if (val1 < 45) {

            forward(254, 255);

            delay_ms(60);

        };

        if (val1 > 76 && val1 < 86) {

            forward(255, 250);

            delay_ms(80);

        };

        if (val4 == 0) {

            forward(255, 255);

            delay_ms(1200);

            stop();

            break;

        };

        delay_ms(5);

    }

}

void turn_left()

{

    left(254, 250);

    delay_ms(800);

    while (val4 < 45) {

        packet_received();

        left(254, 250);

        delay_ms(250);

    }

    stop();

}

void turn_right()

{

    right(254, 250);

    delay_ms(800);

    while (val4 > 50) {

        packet_received();

        left(254, 250);

        delay_ms(250);

    }

    stop();

}

void main(void)

{

    init();

#asm("sei")

    preliminary();

    while (1) {

        // soft_start();  //'heating' the system ^_^

        //straight(); 

        //turn_left();

        while (1) {

            packet_received();

            forward(0, 255);

            if (val1 < 45) {

                break;

            };

            delay_ms(1);

        }

        stop();

    }

}

e0ne199

Posted: May 22, 2012 - 04:01 PM

Joined: Mar 27, 2010
Posts: 64

david.prentice wrote:

i'm afraid if i change it become getchar() the process will be halted because getchar() will loop until the packet is received...CMIIW..and if i do so, the interrupt will be useless, or?

bobgardner

Posted: May 22, 2012 - 04:09 PM

Joined: Sep 04, 2002
Posts: 21390
Location: Orlando Florida

The interrupt reads the char from the uart and puts it in an array/buffer/queue (my mental model is an array. Old basic and fortran habit). Kbhit() returns true if there is something in the array (input index has been incremented), getchar pulls out a char from the output index. The indexes chase each other from 0 up to max then back to zero.

_________________
Imagecraft compiler user

david.prentice

Posted: May 22, 2012 - 05:31 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

First off. Please edit your last post to remove the COPY of my post. Long stretches of code are ok as one-offs. It serves no purpose to repeat them verbatim. [done that for him - moderator]

Quote:

i'm afraid if i change it become getchar() the process will be halted because getchar() will loop until the packet is received...CMIIW..and if i do so, the interrupt will be useless, or?

Read any book on C. Think about your PC. Think about most things in life. Your PC receives all your key-presses via interrupts. Even if it was busy writing to disk, reading a DVD, downloading from the internet.

You call getchar() when you want to see the next key in the queue. If there is not one available, it waits until there is.
This is why you call kbhit() to check first. Only call getchar() when kbhit() says there is something to get.

Try any of the CodeVision examples with buffered RX interrupts. You will see that nothing is lost. (unless you are silly, a 64 byte buffer is fine for most AVR projects)

I am still fascinated by whether people really do work with unformatted code. And if so, how do you do it ?

David.

clawson

Posted: May 22, 2012 - 05:36 PM

Joined: Jul 18, 2005
Posts: 62922
Location: (using avr-gcc in) Finchingfield, Essex, England

Quote:

I am still fascinated by whether people really do work with unformatted code.

Or comments. Shocked

_________________

david.prentice

Posted: May 22, 2012 - 05:51 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

I can cope without the comments. If you choose your names wisely, a formatted listing can be understood.

Mind you, I have a pretty good idea what opinion the OP's teacher will have.

Even if the code does not work, if she has documented it well, the student is more likely to impress an employer.

Quote:

I am still fascinated by whether people really do work with unformatted code.

It is a genuine question. When I used to write 6502 ASM, my editor formatted automatically. What was stored on disk was without any indentation.

Are there C editors that do this ?

David.

clawson

Posted: May 22, 2012 - 05:54 PM

Joined: Jul 18, 2005
Posts: 62922
Location: (using avr-gcc in) Finchingfield, Essex, England

Quote:

When I used to write 6502 ASM, my editor formatted automatically. What was stored on disk was without any indentation.

Are there C editors that do this ?

I'll bet the editor was forced to do that in the days when every byte on disk was a precious resource! I doubt that modern C editors have the same impetus to implement such a feature.

_________________

david.prentice

Posted: May 22, 2012 - 06:27 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

Yes, Cliff. I wrote the editor!

Yes, when I started to use PCs with more RAM and more disk, there was little point in continuing with compressed code.

All the same, modern PCs could quite easily format automatically. Personally I am happy with a specific 'format' command. Any auto-anything makes me feel uncomfortable.

Hand-formatting takes very little brain power. The average student could come home drunk. Format her assignment. Collapse in a heap. Still gain a reasonable mark even if the assignment does not 'work' perfectly.

David.

e0ne199

Posted: May 22, 2012 - 08:25 PM

Joined: Mar 27, 2010
Posts: 64

bobgardner wrote:

thx for the detail explanation, i have tested it and it did hold the values first in the buffer before it is called Smile

david.prentice wrote:

First off. Please edit your last post to remove the COPY of my post. Long stretches of code are ok as one-offs. It serves no purpose to repeat them verbatim. [done that for him - moderator]

Quote:

i'm afraid if i change it become getchar() the process will be halted because getchar() will loop until the packet is received...CMIIW..and if i do so, the interrupt will be useless, or?

still not understand with the unformatted code you're talking about. Smile

e0ne199

Posted: May 22, 2012 - 08:42 PM

Joined: Mar 27, 2010
Posts: 64

about this code :

Code:

interrupt [USART1_RXC] void usart1_rx_isr(void)

{

char status,data;

status=UCSR1A;

data=UDR1;

request_=data;

  if(request_==0x20) { putchar1(real_packet[1]);}

  if(request_==0x30) { putchar1(real_packet[2]);}

  if(request_==0x40) { putchar1(real_packet[3]);}     

  if(request_==0x60) { putchar1(real_packet2[0]);}

  if(request_==0x70) { putchar1(real_packet2[1]);}   

  if(request_==0x80) { putchar1(real_packet2[2]);}

  if(request_==0x90) { putchar1(real_packet2[3]);};

  ........

i deliberately place my own code into the codevision ISR() so that i can get direct response when the packet is requested from other devices / mcu...or do anyone have a better way to get a direct response just like what i did with this code anyway? Smile

david.prentice

Posted: May 22, 2012 - 10:24 PM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

You normally have short ISR()s that simply fill buffers or set a simple flag.

Your foreground code examines any flags or empties a buffer as a separate operation.

There is no right and wrong way in software. There are often efficient and inefficient or better and worse techniques.

By all means choose your own approach to interrupts and definitely your own approach to formatting.

Incidentally, atomiczombie apparently writes ASM code in a single monster file with no indentation.
Yet he produces some impressive software and hardware.

David.

e0ne199

Posted: May 25, 2012 - 12:11 AM

Joined: Mar 27, 2010
Posts: 64

david.prentice wrote:

thx for the response.. btw i have 2 last question :

1) Do you know how to flush USART rx if it is not interrupt-driven?

2) btw if i use kbhit(), will the rx receive the data from outside in correct order?

thx before Smile

david.prentice

Posted: May 25, 2012 - 07:50 AM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

For buffered input, you examine whether there is anything in the buffer.

Code:

// for interrupt-driven RX on USART0:

#define kbhit()    (rx_counter0 != 0)

For polling, you check the USART itself.

Code:

// for polled RXC

#define kbhit()    (UCSR0A & (1<<RXC0))

You flush a buffer in exactly the same way for either method. i.e.

Code:

while (kbhit()) getchar();

kbhit() is just a common name for a function/macro that tests whether there is a byte available.

Since you have CodeVision with its very capable CodeWizard, you might just as well try your own experiments. e.g.

Code:

#include <delay.h>

char c;

printf("type away regardless.   Typing 'S' will sleep the display for a second\r\n");

while (1) {

    if (kbhit()) {

        c = getchar();

        if (c == 'S') delay(1000);

        putchar(c);

    }

}

If you use interrupts, you will not lose any characters at all. If you use polling, any keys typed while the AVR is 'delaying' will be lost.

As I tried to explain earlier, your PC does not lose characters when the disk is running or you are playing a CD. Your PC works like the Wizard interrupt.

David.

e0ne199

Posted: May 25, 2012 - 12:54 PM

Joined: Mar 27, 2010
Posts: 64

david.prentice wrote:

For buffered input, you examine whether there is anything in the buffer.

Code:

// for interrupt-driven RX on USART0:

#define kbhit()    (rx_counter0 != 0)

For polling, you check the USART itself.

Code:

// for polled RXC

#define kbhit()    (UCSR0A & (1<<RXC0))

You flush a buffer in exactly the same way for either method. i.e.

Code:

while (kbhit()) getchar();

Code:

#include <delay.h>

char c;

printf("type away regardless.   Typing 'S' will sleep the display for a second\r\n");

while (1) {

    if (kbhit()) {

        c = getchar();

        if (c == 'S') delay(1000);

        putchar(c);

    }

}

wew, what a great explanation! Smile

thx for your help, i'll test it soon Smile

e0ne199

Posted: May 26, 2012 - 01:24 AM

Joined: Mar 27, 2010
Posts: 64

oh yah, one more question... Very Happy

@bobgardner said that i may not put my modified code inside codevision's ISR() and what he said is right, if i put my modified code inside ISR() it will hang my mcu...btw do you know how to do a fast call without using ISR()? at least it wouldn't take time more than 500ms on each call, thx again for the help Very Happy

david.prentice

Posted: May 26, 2012 - 08:23 AM

Joined: Feb 12, 2005
Posts: 16545
Location: Wormshill, England

I suggest that you leave the ISR() unchanged. The Wizard creates perfectly correct code.

You should put any program logic into the foreground code (which will call getchar() as required)

Since you never lose any keypresses, you can process at whatever speed you like. In fact the AVR will be able to do more work because it is never waiting for hardware.

Have you tried my example program?

David.

Jump to:

All times are GMT + 1 Hour

Previous 1, 2, 3 Next All

AVR Freaks Forum Index » AVR (8-bit) Technical Forums » AVR forum

AVRFreaks.net

Search