I2C change SDA port direction

[cicga]

Hi all,

protocol I2C need to change direction of SDA line from input to output for send ACK bit.

in XMOS example they just writing:

in one case - i2c.sda ;> Temp;
and in other case i2c.sda <: Temp;

but SDA port should be an input for get data and output for send ACK bit. :shock:

but I did not find how they change port direction on fly.

thanks

cicga

[Bianco]

An output operation followed by an input operation will automatically set the port to input.
The port has to be declared as a normal port (port portname) though.

[cicga]

Hi Bianco,

thanks for make it clear just how port should be declare - inp or out or does'nt matter?

could you pls point me where did you find this info?


best

cicga

[Ross]

Something like this?

Code: Select all

out port i2c_scl = XS1_PORT_1A;
port i2c_sda = XS1_PORT_1B;

[Bianco]

A port without a direction specified like for example the i2c_sda port in Ross' example is a bidirectional port and an output operation will set it to output and an input operation will set it to input.

Chapter 3.3 of the ports specification discusses this briefly (though without XC example).

[cicga]

thanks

its clear now

cicga