i have one of these
http://www.ebay.com/itm/PCF8574-IO-Expansion-Board-I2C-bus-to-8-bit-Parallel-/150950688511?pt=Keyboards_MIDI&hash=item23255cb6ff
but due to cost just want to make my own. there is a device on the SCL and SCA line (cap maybe) really not sure but what is it and is it neccessary
thanks
I guess these are pull-up resistors. They shouldn't be on the PCB because they should exist only once per I2C bus. If you connect multiple boards of this type you might get a problem.
They shouldn't be on the PCB because they should exist only once per I2C bus.
That is why they are connected through links so you can remove the pull up resistors if you have more than one board.
You connect the two signals to the I2C lines on the arduino, this will change depending on what arduino you have. On a Uno this will be A4 & A5.
Look at the wire examples for how to talk to it and look at the data sheet for the chip to see what to say to it.
ok so when i make my own and have multiple i2C chips on the same bus i should just have 1 set up pill up resistors.
i looked at some of the i2C examples and they are suggesting 10k ohm resisters and will tie to Vdd. thanks
Well I would use 4K7 resistors in place of 10K