I2c comms between boards

[JAY X]

Hi!

I have a 500 series stereo/dual mono compressor idea, that may involve using i2c communication between each compressor microcontroller (AVR atmega4809).

Each mono compressor has a part of its sidechain controlled by this microcontroller. Ok so far. But i also want to communicate each microcontroller between them, by i2c. 10-15cm two wires, SDA & SCL. Is that all? That simple? Can I use shielded wire with gnd cut at the receiving end? twist the wires? or there is something more? dedicated transceivers for differential transmission?

jay x

 

[PermO]

I've connected a small display unit to an Arduino using 15cm of twisted wire, works fine.

Maybe sheild it because it's an audio device, single sided connection of sheild is fine.

 

[JAY X]

Hi PermO!

Ok, Thank you! I'll try twist and shield!

jay x

 

[Matador]

The thing to watch out for is the maximum rise time of the SDA line, when transmitting a 1 down the line. A 1 is sent by the bus master "letting go" of the SDL line, which leaves the pull-up resistors to pull the line "high" through the bus capacitance. If you have a long(ish) line, and have significant capacitance due to shields, you may not ever be able to transmit a '1' down the line.

https://www.ti.com/lit/an/slva689/slva689.pdf

From figure 3, with a 4.7kOhm pull up, total bus capacitance cannot exceed about 250pF in standard mode (100kHz). In fast mode (400kHz) it is far less (roughly 50pF).

 

[totoxraymond]

I made a console with more than 1m length of i2c using flat cables. No worries. I used a buffer in the chain before that 1m length but i'm not even sure it was necessary.

I2c is also used for computer peripherals (that's how a vga or dvi monitor will tell the computer about its brand and model). So it can deal with quite a bit of length.