Log and retrieve data using Orange Pi

Recently I bought an Orange Pi PC which is a small single-board computer. It is similar to Raspberry Pi 3 but costs about one third of the price. To testing it's long term functionality and reliability for future purposes I built a setup where I use it as a data logger in the following Internet of Things project.

The plan was to send wirelessly some sort of real time data to the Pi (aka Server), which needs to be immediately stored in database. Secondly, the timestamped data should be retrieved anytime using a browser.

As data source I used the DS18B20 digital temperature sensor which I connected to a Wifi module - NodeMCU - based on the well known ESP8266 Wifi enabled microcontroller. To send the temperature values I wrote an application in the Arduino environment of ESP8266, where I managed to read the sensor in every minute and post the value simply over TCP connection. So at now only the text formated payload goes above the TCP layer.

The measured temperature is being displayed locally at the station on a cheap Nextion Human Machine Interface.

Later on when the whole setup worked I got the idea to get in the business an another temperature source, so I put the breadboard below with sensor and wifi in another room.

This time I wanted to test for this purpose the cheapest ESP8266 module - the ESP-01. It worked.

On the server side first I installed Armbian on the Orange Pi which is a Linux distribution for ARM boards. After that next Apache and PHP for webserver to display the temperature values in browser later; WiringOP to interact with peripheral (LED and character display) connected directly to Pi; MySQL database to store the timestamp-temperature datapairs; Node-RED to redirect the incoming data to the database and show something on the display.

The operating mechanism of the Pi can be divided into two parts: log data into database; retrieve and show temperature in webbrowser.

The first part was implemented in Node-RED, which is a graphical programming interface based on javascript.

The incoming text formated temperature data from the two Wifi stations appears here on the left side as TCP-inputs (grey nodes). Upper stands for the Wifi station #1, lower the #2. When there is incoming data on these inputs, the first LED (LED string) on the breakout breadboard of Pi will flash once - using LedBlinker and LedBlinker EXEC nodes. Using a function node the data will be modified/edited to a valid INSERT MySQL query. The two separate datatables for temperature values are accessed via melesolDB named nodes (orange).

I made a tiny C app compiled with GCC running in the background using node-daemon (light orange node on the right side named /root/GccProjects/TestProjectI2c/TestProjectI2c2). This node executes the bash command written inside, and constantly takes input on the left side, which serves as STDIN for my app. String coming here inside will be identified: LCD background LED on/off, temp1/temp2 data, exit command. The STDOUT of my app is redirected to debug window on the right (green node).

Retrieving temperature values are implemented with PHP scripts and Google Line Chart javascript code for drawing charts. Here the PHP code basicaly reads the value pairs from both datatable of last 24h, and feeds them to chart.

The result is shown below as it can be seen in a browser:

For now that's all what this setup does. Actually it can be expanded with more sensors, but at now I just want to test the system in a long term period.