Ok, strange thing 
I have connected my setup today to check the commands for you and I2C seems to work fine. When I'm sending "M260 A3 B65" I can see the state changes according to address being sent:
Of course Duet is still saying "Error: M260: I2C transmission error", but now I know that is because I'm not sending ACK from my side.
So the last time I have probably connected something wrong, sorry for bothering you
Hi, I have a 3D printer in which the printing proccess has to be done by streaming G-codes by the ethernet. Telnet channel works fine and the printing proccess runs without major issues. The problem is that I would like to use Duet3D Laser Filament Monitor. I know that it works with printing from the SD card, but printing from the card is not available in my case.
I have tried to modify the firmware by adding a custom M-code which executes StartPrinting(true) before I start streaming G-codes, but it hangs the board. Is there an easy way (or not that easy) to tell Duet3D that it is in printing state (and has to use filament monitor) while I'm sending G-codes by telnet?
Best regards,
Krzysztof
Ok, strange thing
I have connected my setup today to check the commands for you and I2C seems to work fine. When I'm sending "M260 A3 B65" I can see the state changes according to address being sent:
Of course Duet is still saying "Error: M260: I2C transmission error", but now I know that is because I'm not sending ACK from my side.
So the last time I have probably connected something wrong, sorry for bothering you
Great, thank you very much!
Thank you for lightning fast answer 
Firmware updated to 2.01(RTOS) (2018-07-26b2), resistors are 4.2K (I haven't got 4.7 at the moment), still the same reply from Duet.
Hi,
I would like to ask you for help with the problem that I have encountered today. I would like to send data to my board connected to Duet by I2C. For now I have installed pull-ups on Duet's TWCK0 and TWD0 and connected them to logic analyzer (grounds are connected). When I'm trying to send something using M260, the Duet says:
M260: I2C transmission error
And the logic analyzer shows nothing (high on both lines). I have tried to send different data using examples from Gcode documentation "M260: i2c Send Data".
My setup is DuetEthernet V1.02, firmware 2.01beta2(RTOS).
Thank you very much for your help!
Chris