Beginner I2C Questions

[rocket_troy]

I have a PIC18F13K50 (Master) which I'm trying to transmit some I2C commands to a DTMF chip (PCD3312 - Slave).
The processor has an inbuilt 16Mhz oscillator so I assume I include a "DEFINE I2C_SLOW 1" declaration to operate the I2C in standard 100KHz mode? Do I need to set any additional I2C timing registers directly through the processor or does PBP look after that?
What are the suggested resistance values for the data and clock lines for I2C?
Do I need to set these pins to digital inputs or just inputs?

Thanks for any help,

Troy

[rocket_troy]

Oops:
What are the suggested resistance values for the data and clock lines for I2C?

should read: What are the suggested pull up resistance values I should use for the data and clock lines for I2C?

Thanks,

Troy

[andywpg]

Oops:
What are the suggested pull up resistance values I should use for the data and clock lines for I2C?

4.7K There's a good diagram in the manual - look at the I2CREAD command.

I've never bothered with I2CSLOW - PBP seems to set up all the registers by itself and it works fine.

Good luck!

[HenrikOlsson]

Hi,
I've never actually done anything with I2C so I'm no expert - by far.
But, in case there's some confusion, the I2READ / I2CWRITE commands are both bit-banged routines meaning they do not use the I2C peripheral (the MSSP-module) built into several PICs. This means that there really are no registers to setup except enabling the pin to work as a digital I/O, ie. make sure any analog functions are turned off on the pins in question. It also means that you can use "any" pins for the I2C-lines, not only those designated SDA and SDL in the datasheet - those are for the MSSP module which I2CREAD/I2CWRITE doesn't use.

/Henrik.

[rocket_troy]

Thanks for that guys! I'm really glad I asked! Your intuition was spot on Henrik, I was under the naive impression PBP used the MSSP module of the PIC.

Cheers,

Troy

[rocket_troy]

Henrik and co,
Just to clarify, do I need a port with digital I/O capabilities to function for PBP's I2C communications or can I use a digital input only port? I'm using the PIC micro as the master only.

Thanks,

Troy