Wio Terminal: Display Sensor Data and HTTP Post to machinechat's JEDI One


This project sets up a Seeed Wio Terminal to read it’s internal light sensor, show and graph the data on it’s LCD display and post the data to machinechat’s JEDI One IoT data platform. Arduino is used to implement the Wio Terminal application and JEDI One is installed and running on a Raspberry Pi 4.



  • JEDI One
    JEDI One is a ready-to-use IoT data management software solution. Capabilities include: collect data from sensors, devices and machines; build intuitive real-time and historical data and system view dashboards; create rules to monitor and respond to data conditions automatically; receive alert notifications by email and SMS.
  • Arduino
    Arduino is an open-source electronics platform based on easy-to-use hardware and software.


Wio Terminal is a standalone Arduino/MicroPython compatible SAMD51-based microcontroller evaluation platform with WiFi/Bluetooth powered by a Realtek RTL8720DN. It is equipped with a 2.4” LCD Screen, onboard IMU(LIS3DHTR), Microphone, Buzzer, microSD card slot, Light sensor, and Infrared Emitter(IR 940nm). For this project, Arduino is used to implement a simple IoT sensor that reads the internal light sensor, displays and graphs the sensor data on the Wio Terminal’s integrated LCD display and HTTP posts the data to machinechat’s JEDI One IoT data platform. JEDI One is configured to display the light sensor data on the Sensor Dashboard.

Set up the Wio Terminal platform for the Arduino application

1 - Set up Arduino on the Wio Terminal. See link Getting started with Wio Terminal
note: make sure Realtek RTL8720DN firmware is updated per Update the Wireless Core Firmware

2 - Install libraries needed for application. Add these libraries thru Arduino’s Library Manager:

note: add “Free_Fonts.h” and “arduino_secrets.h” files to project directory (Free_Fonts.h is located in ~/Arduino/libraries/Seeed_LCD_master/examples/320 x 240/All_Free_Fonts_Demo)

3 - Code walkthrough (filename: WioTerminalLightSensorGraphWiFi.ino)

Initial setup and connect to Wifi network

#include <rpcWiFi.h>
#include <HTTPClient.h>
#include "arduino_secrets.h" 
#include <ArduinoJson.h>

#include"seeed_line_chart.h" //include the library
#include"Free_Fonts.h" //include the header file
TFT_eSPI tft;

// for LCD line chart
#define max_size 50 //maximum size of data
doubles data; //Initilising a doubles type to store data
TFT_eSprite spr = TFT_eSprite(&tft);  // Sprite 

// Create a unique ID for the data from Wio Terminal running this code
const char* jediID = "WioTerminalLightSensor";
///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID;        // your network SSID (name)
char password[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)

// Change the following IP to your computer's IP running the server, make sure the Port also match
// IP address of server or Raspberry Pi running Machinechat JEDI software
// If you changed the JEDI port number, replace 8100 with the new port
const char* yourLocalIp =  "";

void setup() {
  tft.fillScreen(TFT_WHITE); //Black background
  spr.createSprite(320,120); //try half screen
  tft.setFreeFont(FF19); //select font
  tft.drawString("Light Sensor",10,120);//prints string at (10,10)

  pinMode(WIO_LIGHT, INPUT);  //Wio Terminal internal light sensor
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) { //Check for the connection
  Serial.print("Connected to the WiFi network with IP: ");

Display /chart light sensor on LCD display and set up sensor data in JSON format and send to JEDI One using HTTP post

void loop() {
   //prep for sending HTTP to JEDI One
   String postData1; //Json string   
   tft.setFreeFont(FF24); //select font
   int light = analogRead(WIO_LIGHT);
   char value[7] = "     ";

   Serial.print("Light value: ");  //debug, can be commented out
   itoa(light,value,10);  //convert light sensor integer value to character
   tft.drawString(value,60,170);//prints data at (x,y)
   if (data.size() == max_size) {
        data.pop();//this is used to remove the first read variable
    data.push(1.0 * light); //read variables and store in data

  //Settings for the line graph
    auto content = line_chart(20, 10); //(x,y) where the line graph begins
                .height(tft.height() - 140) //header.height() * 1.5) //actual height of the line chart
                .width(tft.width() - content.x() * 2) //actual width of the line chart
                .based_on(0.0) //Starting point of y-axis, must be a float
                .show_circle(false) //drawing a cirle at each point, default is on.
                .value(data) //passing through the data to line graph
                .color(TFT_PURPLE) //Setting the color for the line
    spr.pushSprite(0, 0);
   //Following code creates the serialized JSON string to send to JEDI One
   //using ArduinoJson library
   StaticJsonDocument <200> doc;
   JsonObject context = doc.createNestedObject("context");
   context["target_id"] = String(jediID);
   JsonObject data = doc.createNestedObject("data");
   data["lightSen"] = light;
   serializeJson(doc, postData1);
   Serial.println(postData1);    //debug, can be commented out

// http post code
 if(WiFi.status()== WL_CONNECTED){   //Check WiFi connection status
   HTTPClient http;
   http.begin(yourLocalIp);  //Specify destination for HTTP request
   http.addHeader("Content-Type", "application/json");             //Specify content-type header
   int httpResponseCode = http.POST(postData1);   //Send the actual POST request
    Serial.print("HTTP Response Code: ");
    Serial.println(httpResponseCode);   //Print return code
    Serial.print("Error on sending request: ");
   http.end();  //Free resources
    Serial.println("Error in WiFi connection");
   tft.setTextColor(TFT_WHITE);   //"clear" old light sensor data value

4 - Latest source code for the WioTerminalLightSensorGraphWiFi.ino application is on github at below link:

Set up the JEDI One

1 - If machinechat JEDI One is not already installed on the Raspberry Pi see below:

2 - Set up the JEDI One dasboard

In the JEDI One, select “Dashboards” tab, then select “+” to add a new chart and configure.

Name the chart, select “Chart Type”, select “Source” (WioTerminalLightSensor), select "Property (lightSen), and enter “Refresh Interval”. When complete the dashboard should liook similar to below.



Seeed’s Wio Terminal makes it easy to implement a low cost full color graphical sensor display. The built-in WiFi provides additionally capability to send and receive information over a WiFi network. Using WiFi, the sensor data can easily be sent to machinechat’s JEDI One IoT data management software for additional processing, alerts or other actions.