Help: 18f452 I2c

seoman_79 · Joined: 11 Jul 2006 Posts: 1

Hi, this is my first time!
so, i have a PIC 18f452 and i am trying to use i2c bus,using CCS Compiler

#use i2c(Slave,Fast,sda=PIN_C4,scl=PIN_C3,restart_wdt,force_hw,address=0xa0)
...
#int_ssp
void SSP_isr() {
restart_wdt();
printf(" i2c");
}
...
main(){
...
output_flow(PIN_C3);
output_flow(PIN_C4);

}

i have an ideal start Condition on the bus,and the rigt address (my signal si about 50Hz),but the interupt seems not to work well.
Anyone can help me,please?

Thanks,

mario

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

1. Post code using the "code" button. It retains the format.
2. Post complete code. You don't have any PIC info
3. Always have a forever while loop at the end of the test to prevent the PIC from going to sleep.((CCS compiles puts this sleep command in for you))
4. There isn't a function output_flow.. I figured you wanted output_low, but this would in turn override the I2C code
5. You never turned on the interupts. To do this enable the int you want to use, provide a ISR and turn on interupts global.

try this

Ttelmah · Guest

Also though, do not pull the C3/C4 pins down. The slave, needs to listen to the pins, and only activate the data pin when ordered to do so. At present, the code is setting the pins as outputs, and pulling the data and clock line low, thereby overriding the I2C peripheral, which can therefore not work.

Best Wishes

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

One word of advice, never _ever_ put a printf() statement inside an interrupt handler. Printf() can create a massive amount of code and an interrupt needs to be as short as possible. Set a variable, inside the interrupt, and then evaluate it in main(). If it is set then print something and clear the variable. You'll find this is the better way to do things as you begin to write more extensive and complicated code.

Ronald