P18f4550 i2c and ST

[rk396]

Ok, i'm at the end of my rope on this one. I'm like 1 step past beginner here.

Im trying to interface a p18f4550 to an eeprom vie I2C. The routines hang on the wait for ACK from the slave.

I've tried teh built in I2c functions, software functions from C18. I have written my own, and tried various routines i've found on the internet.

the problem. PortB.RB1 is NOT acting like a schmitt trigger input.

I slowed down the transmit function my adding some delays, and hooked up a Powered LED to each PortB 0, and 1. PortB.0 acts accordingly basically lights on a 0, and is off on a 1. Porb.1... nothign. If i switch the def for the clock and data, meaning portB.0 is now the clock. it pulses as expected, and the data line shows nothing.

a crude way to debug i know.

I've configured portb to be all digital thru the config bits and thru the Adcon2.

Am i missing somehting? I can post code if necessary. is the clock supposed to act like an ST or just as an output? All the docs that i found state that both SDA and SCL should be ST's with a pull up resistor (which i have ~10k).

I hope someone can point out the thing that i'm missing.

thanks

 

[Ian Rogers]

Which functions are you using.. Usually this works straight off the bat... Are you using ANY interrupts atall? In C18's example they switch back on the interrupts too early, I modified the code slightly to make it work.

You will need to change the port and processor speed.

 

[rk396]

Ian,

Thanks for the quick reply. Also thanks for the code... i'll give it a try.

I would have thought it should work right out of the box too... i'm sure it's something simple i'm missing. I am not using any interupts in my current version. I tried the software version, and the hardware version that comes with the C18 compiler. I'm off to try your code. thanks again.

 

[rk396]

ok, the routines worked THANK YOU very much.

At first glance they look like the ones i was using, not sure what my deal was. just glad it's now working.

 

[Ian Rogers]

Good, I know how hard it is when something "just doesn't work" you can look at it all day....