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AntonioB
Joined: 25 Oct 2007
Posts: 7
Location: Puebla Mexico
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| I2C multi byte Master-Slave |
 Posted: Thu Oct 25, 2007 12:48 pm |
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Hi there, im been using PICS for a time now, but im new using the I2C comunication, im trying now just to send 3 bytes of information from master(18F4550) to the slave(18F4550), then store them in the slave in to a buffer and use that data to display the values in a LCD.
The LCD its working just fine, it reads bytes and so, but the problem is that i cant reade the 3 bytes, i just get 1 right and the ohter apeear as -96
so i have been searching for a post where they use multiple bytes but i didnt find any one, maybe u can help me out guys, ill be very gratful, thanks to all.
Here is the code. i just send to bytes for now,
MASTER
| Code: |
#include <18F4550.h> //PIC utilizado
#fuses HS,NOWDT,NOPROTECT,NOLVP //Configuramos los fuses
#use delay (clock=4000000) //Oscilador a 4Mhz
#use fast_io(b) //Optimizamos E/S del PORTB
#use fast_io(c) //Optimizamos E/S del PORTC
#use i2c(master, sda=PIN_B0, scl=PIN_B1) // Configure Device as Master
//Programa principal
void main(void) {
while(true){
i2c_start();
i2c_write(0xA0); //Slave adress
DELAY_MS(100);
i2c_write(0x0A); //first data to be display
DELAY_MS(100);
i2c_write(0x0F); //second data to be display
DELAY_MS(500);
i2c_stop();
DELAY_MS(200);
}
}
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THen the SLAVE, that also displays the data
| Code: |
#include <18F4550.h> //PIC utilizado
#fuses HS,NOWDT,NOPROTECT,NOLVP //Configuramos los fuses
#use delay (clock=4000000) //Oscilador a 4Mhz
#use fast_io(b) //Optimizamos E/S del PORTB
#use fast_io(c) //Optimizamos E/S del PORTC
#use i2c(slave,address=0xa0,sda=PIN_B0, scl=PIN_B1,slow) // Configure Device as Slave
#include "lcd.c" //Incluyo LCD.C
BYTE bufferTemp [3],state,incoming;
//char temp=0x05;
//=========interrupcion para I2C======
#INT_SSP
void i2c_interupt (void)
{
state = i2c_isr_state();
if(state < 0x80) //Master is sending data
{
incoming = i2c_read();
if(state == 1) //First received byte
bufferTemp[0] = incoming;
if(state == 2) //Second received byte
bufferTemp[1] = incoming;
}
}
//Meotodo para desplegar tecto y temperatura en LCD
void lcd_desplegar(void) {
while(TRUE){ //Condicion para que siempre se ejecute el metodo
printf(lcd_putc,"Temperatura1:%d",buffertemp[0]); //imprime el texto1 junto con el valor de la varibale temp
delay_ms(1000); //retaro
lcd_putc( "\f"); //borra display
printf(lcd_putc,"Temperatura2:%d",buffertemp[1]); //imprime el texto1 junto con el valor de la varibale temp
delay_ms(1000); //retaro
lcd_putc( "\f");
printf(lcd_putc,"Temperatura3:%d",buffertemp[2]); //imprime el texto1 junto con el valor de la varibale temp
delay_ms(1000); //retaro
lcd_putc( "\f");
}
}
//Programa principal
void main(void) {
enable_interrupts(GLOBAL);
enable_interrupts(INT_SSP);//interruptions
buffertemp[0]=0x01;
buffertemp[1]=0x02;
buffertemp[2]=0x03;
lcd_init(); //inicialisa el LCD
lcd_desplegar();//llama al metodo para deslpegar texto en LCD
}
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I have already try multiple ways, but no one works, the most i can do its to read succesfully one byte but no more, thanks for your help. |
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Ttelmah
Guest
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| Posted: Thu Oct 25, 2007 4:00 pm |
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Series of things.
First, get rid of the 'slow' declaration in the slave. The slave has _nothing to do with I2C timing_. If you want to use 'slow', this needs to be in the master.
Next, you need to read the byte whenever the I2C_ISR_STATE is below 80. Read the byte, then test the state, to work out where to put it.
Obviously, presumably you do have pull-up resistors on the bus?.
I'd shorten the delays rather massively.
ex_slave.c, shows how to handle an indexed transfer to an address. If you simply reset your counter, then use:
| Code: |
#INT_SSP
void ssp_interupt ()
{
//Only have variabled that need to be 'global', global.
//reduces risk of data getting accidentally corrupted...
BYTE incoming, state;
static int address;
state = i2c_isr_state();
if(state <0x80>2) address=2; //prevent overrun
}
}
if(state == 0x80) //Master is requesting data
{
i2c_write(0); //Dummy return to ensure I2C doesn't get confused
}
}
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Best Wishes |
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rnielsen
Joined: 23 Sep 2003
Posts: 852
Location: Utah
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| Posted: Fri Oct 26, 2007 9:36 am |
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I've never used the i2c_isr_state() command but perhaps the answer to my question might help AntonioB a bit.
The help file states that a value of 1-0x7F means the Master has written data. Does this value increment starting from 1 with each byte that is written or is it some kind of arbitrary value? Also, a value of 0x81-0xFF means a transmission is finished and ACK'd and a write needs to be performed. Does this value increment just like the first question I posed?
I've always manipulated the registers directly and I'm just curious about this command.
Ronald
If the world were to start spinning faster, would be all start losing weight? |
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AntonioB
Joined: 25 Oct 2007
Posts: 7
Location: Puebla Mexico
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| Posted: Mon Oct 29, 2007 5:21 pm |
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| ok, thanks alot for your answer im going to check that, thanks |
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Guest
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| Posted: Tue Oct 30, 2007 4:43 pm |
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The code now works just right, I just change the state condition, and now I can send and receive data thanks for the help.
| Code: |
#INT_SSP
void i2c_interupt (void)
{
state = i2c_isr_state();
if(state < 0x80) //Master is sending data
{
incoming = i2c_read();
if(state == 0) //First received byte
bufferTemp[0] = incoming;
if(state == 1) //Second received byte
bufferTemp[1] = incoming;
if(state== 2)
bufferTemp[2] = incoming;
if(state== 3)
bufferTemp[3] = incoming;
if(state== 4)
bufferTemp[4] = incoming;
if(state== 5)
bufferTemp[5] = incoming;
if(state== 6)
bufferTemp[6] = incoming;
}
if (state == 0x80)
{
i2c_write(0);
}
} |
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