Creating a Human-Machine Interface (HMI) Web Application

Simple Embedded Monitor and Control Dashboard

Final HMI Web Application
Final HMI Web Application

In this guide, we’re going to learn how to create a very simple PHP web application that will read and display real-time CPU temperature data and control an LED using javascript AJAX calls from a web browser anywhere in the world. In the real world, you’d want to monitor something more interesting, like equipment or sensors connected to ADC, CAN, RS-485, RS-232 ports and other GPIO pins. Or how about monitoring voltage input? You’d also want to be able to control your connected equipment using digital output signals. This guide provides an introduction to the concepts that will help get you started in the right direction. All source code is available in the tarball hmi-example-web-app.tar.

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Getting Current Voltage Input (VIN) on TS-7250-V2

Here’s an example program our engineers might find useful. Jesse Off, our lead engineer, wrote this simple program to get the voltage input (Vin) on the 8 – 28 VDC power rail on the TS-7250-V2 (Rev. B only). Without going into too much detail about implementation of the SiLabs microcontroller, there is a register which is used to store various ADC values, including Vin. This example program basically polls this 19 byte register via I2C interface, accounts for the voltage divider (see TS-7250-V2 schematic), and spits out the Vin value. So, without further ado, here’s the code:

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