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Topic: Disable I2C pull-ups in Attiny85 using TinyWireS library (Read 175 times) previous topic - next topic

Jul 01, 2014, 03:29 pm Last Edit: Jul 01, 2014, 03:33 pm by imm_yohan Reason: 1
I'm trying to create communication between RPi, two Atmega328P and one Attiny85 via I2C using this library http://playground.arduino.cc/Code/USIi2c from rambo https://github.com/rambo/TinyWire/tree/master/TinyWireS.
I don't have any level shifters nor any MOSFETs. But I found on the Internet that it's possible to make safe communication if disable pull-ups to 5V. In Atmegas it was simple. But I don't know how to make it in attiny without interfering with library. In examples it's said
    * Reminder: taking care of pull-ups is the masters job

But I've tested it with multimeter and  pin 0(PB0/PCINT0) was high and PB2 was low without connection to anything in slave mode.
In this file here https://github.com/rambo/TinyWire/blob/master/TinyWireS/usiTwiSlave.c there is lines like this everywhere
Code: [Select]
I don't know maybe my test was wrong and I thought slave release pin so it can be pulled up and not writes HIGH.
Is it save to connect it as it is or I should find out how to disable this HIGH state?

//Maybe I'm in the wrong forum branch. Sorry.

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