Hello @HarishKumar,
sorry for the late reply.
Evok in version 1 is no longer supported (didn't you mean Evok-mini?). The current version of Evok is 2.1.x. As the first step, you should try to download and install the latest version via Debian package subsystem:

apt-get update
apt-get install evok

Or directly:

wget https://repo.unipi.technology/debian/pool/e/evok_2.1.2_armhf.deb
dpkg -i evok_2.1.2_armhf.deb

Hello @knebb, as @ntd wrote there is no need to use the Evok (which is, basically a bridge between Modbus server and several web-service interfaces). The simplest option for direct access from a C/C++ application should be the sysfs interface. Of course, a Modbus client connected to the internally running Modbus server can be used also.

Yes, it is clear now. You have to implement this kind of functionality by yourself as Evok does not offer it.

It seems there is a misunderstanding. Can you exactly reference the functionality you currently lack (file/line in the Evok 1.0.1 source code) ?

Hello,
Evok should not affect the UART on Unipi 1.1 in any way. Please note that bluetooth interface shares the same pins (GPIOs) on Raspberry Pi 3. For use these pins as the UART, just add dtoverlay=pi3-disable-bt to /boot/config.txt file on your Raspberry Pi 3.

@pavelf Hello, it seems to something around the web-socket (used e.g. for relay state readout) connection is going wrong. The connection should be established just once, not several times per second. Can you double-check JavaScript settings in your web browser (must be allowed) and/or try an another one ?