Hi,
I have an ESP8266-12 and some OLED displays working with the I2C protocol. The maximum distance for I2C is some meters. I need those displays to be up to 15meters away. I am thinking of converting the I2C into RS485 so it can travel this far... Any other suggestion that maybe works?

 

Something like this device. NXP is the parent of I2C and makes the widest range of devices. You may find this device on a pair of boards somewhere.

https://www.nxp.com/docs/en/brochure/75016527.pdf

 

Hi,
I have an ESP8266-12 and some OLED displays working with the I2C protocol. The maximum distance for I2C is some meters. I need those displays to be up to 15meters away. I am thinking of converting the I2C into RS485 so it can travel this far... Any other suggestion that maybe works?

How will the RS-485 transmitter know to tri-state the driver so the receiver can receive an ACK pulse from the slave device? If you don't, the two transmitters will engage simultaneous jabbering. (We actually had a more colorful term for it). A better solution would be an I2C bidirectional repeater with a method of passing the ACK pulses in the required direction.

Missed the link in Post #2. It is in very light blue on my monitor. That's the ticket.

 

How will the RS-485 transmitter know to tri-state the driver so the receiver can receive an ACK pulse from the slave device? If you don't, the two transmitters will engage simultaneous jabbering. (We actually had a more colorful term for it). A better solution would be an I2C bidirectional repeater with a method of passing the ACK pulses in the required direction.

Missed the link in Post #2. It is in very light blue on my monitor. That's the ticket.

I suppose can use the PCA9515A as bus repeater, they gives me the 15meters that I want?

 

This does bring up the question of how to transmit very far.
What about 100 meters, 1000 meters?
And i assume two wires only?

I am thinking maybe something custom would be better. You can then also send error check codes and have it auto check. If there is an error the receiver (at the time) can request a repeat of the data. I did this with a Z80 computer board so i could program it from a distance with a PC computer where i could not take a chance on an error in the data getting into the RAM of the Z80 board or the system would crash.

 

Not quite. I2C requires a common ground level. I'm not sure the issue of common mode ground differences is even discussed in the I2C context. I know it is a big deal in industrial networks, like DeviceNet.

 

Go RF. There are so many low cost solutions now available.

 

How about fiber-optics? https://www.coptonix.com/_en/html/i2cfiber.html

 

How about fiber-optics? https://www.coptonix.com/_en/html/i2cfiber.html

Too expensive....

 

Too expensive....

Yeah. I was joking. THE NXP method is the way to go.