Using PORTC & I2C

[Pilot]

I am new in PICC. I am using I2C Hardware in PORTC and i want to use other 6 pins for directly output (or input) numbers between 0 and 63, like
myout=52, without affecting the i2c pins/tris. what is the practical way of doing this? Thanks.

[valemike]

If you use hardware i2c, then the rc3(scl)/rc4(sda) pins are overrided by the MSSP module, so there is no need to worry what you write into the portc or latc bit positions.

Personally, what I would do if I was using software bitbanged i2c on the rc3/rc4 pins, then I would try to make rc0-rc2,rc5-rc7 as inputs. Otherwise i would just set each bit individually. If individual toggling is not an option, then I would do some bitmasks and logical or/and to leave those bits alone.

e.g. You want to write '101x x101' into RC3...

unsigned char temp_c;

temp_c = 0xA5; // 1010 0101


// Anding with 0x18 will give you 000X X000
// Or'ing with temp_c will give you 101X X101
// Thus you leave rc3 and rc4 alone
port_a = (port_a & 0x18) | temp_c;

Unless you are doing the above operations in an ISR, then you are guaranteed that you won't interfere in the middle of an i2c_read or i2c_write, since after all, there is only one thread of execution.

-Mike

p.s. just use the FORCE_HW option in the #use i2c( ) declaration and you don't have to worry.

[valemike]

[Guest]

[valemike]

you mean bitfields in the structs?

Yes that's possible. I've seen examples of that.

I personally haven't used bitfield structs in the past since taking my C++ course in college. I've gotten used to and'ing and or'ing instead.