RE: [avr-gcc-list] ATMega128 TWI problems

[Rune Christensen]

Hello

Have you tried to include avr/signal.h
and use SIGNAL(SIG_2WIRE_SERIAL)

How about the instruction sei(); that must be called to enable interrupts?

Cheers
Rune

> -----Original Message-----
> From: address@hidden 
> [mailto:address@hidden On Behalf Of Nick Brent
> Sent: Sunday, May 30, 2004 7:35 PM
> To: AVR-GCC List
> Subject: [avr-gcc-list] ATMega128 TWI problems
> 
> 
> Hey all,
> 
>     I've been banging my head against this problem for two 
> days now, and I figure I need to get some outside help. The 
> code below is a dumbed down version of some code I wrote to 
> interface with the ATMega128 TWI (or I2C) peripheral. At 
> first the problem I thought I was having was that the 
> interrupt handler wasn't picking up control when it was 
> called, but now I'm not sure what the problem is exactly.
> 
>     What happens when I run this code on my chip is that the 
> internal pull-ups are enabled and the line goes high (which 
> should happen), "Ready..." is displayed on the LCD (which 
> should happen), The LCD is cleared and the SDA line goes low 
> (which should happen when sending a START signal), but then 
> nothing happens after that. The 'dubug' sub-function is 
> called in both cases where the interrupt is executed or not, 
> but nothing ever shows up on the LCD. I know the problem 
> isn't in my LCD or dubug code because I've used these 
> subfuctions in many applications without a problem. 
> 
>     Any input anyone could give me would be very appreciated. 
> The code is for my robot which I'm trying to get ready for 
> PDXBot.04 mini-sumo competition next weekend, so I'm kind of 
> in a crunch. Thank you very much in advanced.
> 
>                                         Sincerely,
>     
>                                                 -Chris Troutner
> 
> -------------------------->Begin Code<---------------------
> /*********************************************
> Project : srf085.c
> Version : 1.0
> Date    : 5/30/2004
> Author  : Chris Troutner                            
> Comments: This program is a dummbed down version of SRF083.c.
>    It's an attempt to get the TWI inteurrpt to fire.
> 
> 
> Robot Type:   : ModelT
> *********************************************/
> 
> #include <modelt.h>
> #include <avr/interrupt.h>
> 
> char t[16]; 
> 
> void dubug(uint16_t level);
> 
> void dubug(uint16_t level) {   
>  asm volatile ("cli"); //Turn off all interrupt sources
> 
>  clr_lcd();
> // strcpy(t,"test");
>  sprintf(t,"Er: %d          ",level); //Write the error level 
> value to 't'
>  line1(t);        //Display 't' on the LCD
>  while (1) {};   //loop forever (halt code execution)
> }
> 
> 
> 
> INTERRUPT(SIG_2WIRE_SERIAL) 
> {
> 
> DDRB=0x0F; //set lower 4 bits or portB to output (LED's)
> PORTB=0x0F; //Drive lower 4 bits of PORTB High (Turn on LED's)
> TWCR = (TWCR | BV(TWINT));    //write a logic 1 to TWINT bit 
> to remove inturrupt flag 
> dubug(4); //disply 'Er: 4' on LCD and wait forever.
> }
> 
> int main(void)
> {
> // Declare your local variables here
> 
> init();
> 
> DDRD=0x00;   //set portD to all input
> PORTD=0x02;  //Turn on internal pullups on PORTD
> 
> lcd_init();
> 
> //Turn on LCD so I know SOMETHING is working
> strcpy(t,"Ready...");
> line1(t);
> ms_spin(1000);
> clr_lcd();
> 
> /*------->START TWI Initialization<----------*/
> /* set the I2C bit rate generator to 100 kb/s (see pg. 202 & 
> 206 in Mega128 datasheet)*/
> TWSR = TWSR & 0xFC; //TWPS = 0
> TWBR  = 18;   //TWBR = 18
> //SCL Frequency = (CPU Clock Frequency)/(16+2(TWBR)*4^TWPS)
> //CPU Clock Frequency = 16Mhz for MyRobot Brainboard
> 
> /* Enable Two Wire Interface*/
> TWCR |= BV(TWEN);
> TWCR |= BV(TWINT);    //write a logic 1 to TWINT bit to make 
> sure inturrupt flag is not set
> 
> // enable TWI interrupt and slave address ACK
> sbi(TWCR, TWIE);
> sbi(TWCR, TWEA);
> /*------->END TWI Initialization<--------*/
> 
> /* enable interrupts */
> asm volatile ("sei");
> 
> TWCR = TWCR | (BV(TWINT)|BV(TWSTA)|BV(TWEN)); //send START 
> bit. This should generate an interrupt
> 
> ms_spin(1000); //wait to give interrupt a chance to fire 
> dubug(2);  //send 'Er: 2' to LCD if interrupt doesn't work.
> 
> while (1) {}; //loop forever. We shouldn't reach this point.
> 
> return (1);
> }
> <---------------------End Code------------------------------->
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