How to make dmx512 protocol by using arduino duemilanove

Projects General Guidance
1

Hi
Is there anyone who can help me in this topic
I am making a DMX512 lighting protocol by using arduino duemilanove and dmx sheild
I am having problem in baud rate as the maximum baud rate of arduino duemilanove is 11500k bps.
but i need baud rate of 250k. ATmega 328 datasheet shows that I can get baud rate of 250k but I am not getting it on my oscilloscope.
can anyone help me please

2

priya02:
Hi
Is there anyone who can help me in this topic
I am making a DMX512 lighting protocol by using arduino duemilanove and dmx sheild
I am having problem in baud rate as the maximum baud rate of arduino duemilanove is 11500k bps.
but i need baud rate of 250k. ATmega 328 datasheet shows that I can get baud rate of 250k but I am not getting it on my oscilloscope.
can anyone help me please

3

DMX is not normal 8n1 serial like the arduino IDE expects you have to fiddle with registers to get it setup correctly. There are a pile of libraries out there that can take care of this for you.

4

Hi priya02,

Don't know anything about the Duemilanove but from memory DMX512 is more like RS422 instead of RS232 so may need extra circuitry to function properly.

A quick Google search yields...

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1237578617
http://arduino.cc/playground/DMX/DMXShield
http://arduino.cc/playground/Learning/DMX
5

I am making a dmx512 by using arduino duemilanove
I put ISR to send a dmx packet simultaneously
and in main function i am sending data by using faders
I connect the software serial ports with 25 pin serial port and want to see the output and command line in hyperterminal
I connected by using RS232 IC
I am getting junk ASCII characters but I want the decimal numbers going as data in DMX packet
Can anyone help me
I can put my program

#include<avr/io.h>
#include<avr/interrupt.h>
#include <avr/wdt.h>
#include<HardwareSerial.h>

unsigned char DMXbuffer[512];                  //the 512 DMX channels for a packet of 512 
unsigned char *DMXptr;
int analogPin1 = A1;
int analogPin2 = A2;
int analogPin3 = A3;
int analogPin4 = A4;

int main()
{
  while(1){
  Serial.begin(9600);
  unsigned int NUM_OF_CHANNEL;
  const char stx_pin = 8;  //use pin 8 as softwrae serial transmit pin
  const char srx_pin = 7;      //use pin 7 as software serial receiver pin
  pinMode(stx_pin, OUTPUT);
  unsigned char i=0;
  Serial.println("Enter value of DMXbuffer[] ");
    //unsigned long int val =hex_to_ascii(value);
  EIMSK |= (1 << INT0);    //enable external interrupt INT0
  EICRA |= (1 << ISC01);   //trigger INT0 on falling edge
  PCMSK2 |= (1 << PCIE2);
  PIND |= (1 << PIND1); 
  if (DMXbuffer[0]){ 
  unsigned long int value1 = analogRead(analogPin1);   // read the input pin
  Serial.println(stx_pin,value1);
  Serial.println(value1,HEX);
  PORTD&=~(1<<PIND1);  //disable interrupt
  }
  else if(DMXbuffer[1]){ 
  unsigned long int value1 = analogRead(analogPin2);   // read the input pin
  Serial.println(stx_pin,value1);
  Serial.println(value1,HEX);
  PORTD&=~(1<<PIND1);  //disable interrupt
  }
  else if (DMXbuffer[2]){ 
  unsigned long int value1 = analogRead(analogPin1);   // read the input pin
  Serial.println(stx_pin,value1);
  Serial.println(value1,HEX);
  PORTD&=~(1<<PIND1);  //disable interrupt
  }
  }
}



//interrupt service subroutine attached to INT0 vector
ISR(USART_TX_vect)
{             
  
  int txpin = 1;                  // serial transmit pin, which sends the outgoing data to the MAX481.
  pinMode(txpin,OUTPUT);   
  unsigned char  i; 

  unsigned long baud =250000;    // The baud rate for DMX is 230400bps, since each bit = 4 microseconds.
  unsigned long clockspeed = F_CPU;
  /* F_CPU is a predefined constant equal to the clock speed of the microcontroller.
  *  for the Arduino duomilanove it is 16000000.
  *  I'm going to dump it into clockspeed because I'm worried about it being a signed long,
  *  which could screw up the bitwise math I'm going to do on baudprescale, maybe. */

  unsigned long baudprescale;    
  /* The baud prescale that will be loaded into the
  *  UBRR0H and UBRR0L registers to set the USART baud rate */
  baudprescale = (((clockspeed / (baud * 16UL))) - 1); //
  DMXptr = &DMXbuffer[0];  
  UBRR0L = (uint8_t) baudprescale;
  UBRR0H = (uint8_t) (baudprescale >> 8);
  // Set frame format to 8 data bits, no parity, 1 stop bit.
  UCSR0C |= (1<<UCSZ01)|(1<<UCSZ00);
  //enable transmission and reception
  UCSR0B |= (1<<RXEN0)|(1<<TXEN0);  
  DMXbuffer[0] = (unsigned char) analogRead (analogPin1);
  DMXbuffer[1] = (unsigned char) analogRead (analogPin2);
  DMXbuffer[2] = (unsigned char) analogRead (analogPin3);
  DMXbuffer[3] = (unsigned char) analogRead (analogPin4);

  
  DMXptr = &DMXbuffer[0];
  for ( i=0; i <= 512; i++)
  {
   while(!(UCSR0A & (1<<UDRE0)));
   UDR0 = *DMXptr++;
 } 
  DMXbuffer[0] = (unsigned char) analogRead (analogPin1);
  DMXbuffer[1] = (unsigned char) analogRead (analogPin2);
  DMXbuffer[2] = (unsigned char) analogRead (analogPin3);
  DMXbuffer[3] = (unsigned char) analogRead (analogPin4);
  
 }

Moderator edit: tags added, smileys removed.

6

Can Anyone help me to solve this problem
its really important for me
anybody der