@Jason:

Id be very interested in this as well. Mremy id be happy to nerd out on this with you. I'd love the ability to set up a secondary microcontroller that can send gcode commands to the duet. I have this idea of using a raspeberry pi or ESP8266 with a secondary touchscreen that I can use to make a custom GUI where I can easily customize a list of my frequently used macros. It cant be that hard. I guess I could do it through the WIFI.

Are there any resources or even better, tutorials, that you have run across that explain in detail how to communicate with the duet from outside sources?

Currently I am in the process of setting up a new PC. Once I finish installing all the tools (IDE, toolchains, etc) I will get back and see what we can do. I do prefer to run a stock firmware as I keep all the firmwares up to date on David's code. Having a dedicated Gcode command for I2C and even maybe SPI would be gold from my point of view.

I was not thinking of connecting the extra hardware over long distances just close to the duet board.
Also I was thinking of connecting other micro-controllers that have firmware running on them so more functionality could be implemented instead of just gpio expansion like the SX chip does.
Are the extra fans (beside FAN 0, 1, 2) controlled using this SX chip on the Duet expansion board?

Hi David,

I just want to congratulate you on the fine work you have done.
Would it be possible to also implement the M260 and M261 G codes as I (and possibly others) might want to interface the duet board with extra electronics?
I already have 2 duet boards and would really like to interface them with some custom electronics that talk I2C and SPI.
I would'n mind an SPI version of G codes

Thanks, and keep up the good work.