Tutorials > MKR Connector Carrier > Temperature and Humidity on OLED

Display temperature and Humidity on an OLED display

This basic example teaches you how to create a circuit that uses two Grove modules and requires no soldering. The MKR board you choose may be anyone of the MKR family because the connection is managed through the MKR Connector Carrier.

Hardware Required

Circuit

The connection to the Carrier board requires two standard Grove cables. The DHT humidity and temperature sensor goes to the D0 connector. The OLED screen is connected to the TWI connector.


We did not put a MKR board on the Carrier, but it is required to get the circuit to work, as specified in the bill of materials.

The DHT module uses a specific pin to communicate with the MKR board and it is mapped on D0. This happens because the Grove standard for digital connections follows this rule:

PinFunctrionNotes
pin1DnPrimary digital i/o
pin2Dn+1Secondary digital i/o
pin3VCCPower to module 5V/3.3V
pin4GNDGround


and the module sends SIG on pin 1 that is mapped on the primary digital I/O.

In the picture, the OLED module is shown from component side to let you see the Grove connector. It goes into the TWI male on the MKR Connector Carrier that follows this pin mapping:

PinFunctrionNotes
pin1SCLI2C Clock
pin2SDAI2C Data
pin3VCCPower to module 5V/3.3V
pin4GNDGround


Code

To drive the modules you need to load four separate libraries:

#include <DHT.h>
#include <DHT_U.h>
#include <Wire.h>
#include <SeeedOLED.h>

The DHT module is mapped on D0 when the object dht is instantiated:

DHT dht(0, DHT22);

The rest of the code is straightforward and keeps reading the hum and temp values to be printed on the OLED screen.

Here is the complete sketch

#include <DHT.h>
#include <DHT_U.h>
#include <Wire.h>
#include <SeeedOLED.h>

DHT dht(0, DHT22);

void setup() {

  Wire.begin();                 //initialize I2C in master mode
  SeeedOled.init();             //initialize the OLED
  SeeedOled.clearDisplay();     //clear the screen and set start position to top left corner
  SeeedOled.setNormalDisplay(); //Set display to normal mode (i.e non-inverse mode)
  SeeedOled.setPageMode();      //Set addressing mode to Page Mode
}

void loop() {
  float temp, hum;

  //Read temperature and humidity
  do {
    hum = dht.readHumidity();
    temp = dht.readTemperature();
  }
  while (isnan(temp) || isnan(hum));

  //Print temperature and humidity values on the OLED display
  SeeedOled.setTextXY(0, 0);
  SeeedOled.putString("Temperature:");
  SeeedOled.setTextXY(1, 0);
  SeeedOled.putString(String(temp).c_str());  //print temperature data converted to a c string
  SeeedOled.putString("C");
  SeeedOled.setTextXY(3, 0);
  SeeedOled.putString("Humidity:");
  SeeedOled.setTextXY(4, 0);
  SeeedOled.putString(String(hum).c_str());   //print humidity data converted to a c string
  SeeedOled.putString("%");

  delay(2000);
}
[Get Code]

See also

Getting started with MKR Connector Carrier

Last revision 2018/08/08 by SM