@HarishKumar The evok itself is not designed to handle the logic of your application. That's why we call it API. It is using Tornado which means the server itself runs in one loop so you need to have all the program behavior ready before it is called mainLoop.start(). So if you run an infinite loop anywhere in evok, you stop everything else (reading, setting, all APIs, ...). So I suggest using that APIs, it is much more easier to implement and you have the same functionality. But if you would REALLY want to do it in evok, you would have to prepare your program in a function, all tasks that would take more time would have to be decorated as coroutines and the call has to be yielded in order not to stop the main loop. The logic behind this is a little bit complicated to describe in one post :)

@HarishKumar It's ok. That's why the forum is here. If you visit the web interface of evok, you will see the numbers of IO of the Neuron you are using. In general it is numbered as X_Y where X is the number of group (1-3 depending on S/M/L model) and Y is the number of the Di/Ro/... So for example you would address DI1.4 as a string 1_4 with device type di.

@HarishKumar The internal communication is little bit modified Modbus, I suggest you to use the TCP Modbus: https://github.com/UniPiTechnology/neuron_tcp_modbus_overlay The map of the TCP Modbus registers can be found at http://downloads.unipi.technology