I have an Arduino Uno and I want to connect;

  • RFID Reader (RC522)
  • WiFi Module (ESP8266 ESP-01)
  • SD Card Module
  • RTC (Real Time Clock - DS1307)

Same time but pinouts are not enough. Is there a way to doing this with Uno or I have to buy an Arduino Mega ? I saw "Expansion Sensor Shield"s but I do not know what is the logic of using this ?


  • 1
    It depends. You need to provide more detail. Some of the devices use I²C which can share connections provided they have different addresses. Others use SPI which need individual select pins.
    – Milliways
    Apr 16, 2016 at 8:52

1 Answer 1


Let's see which device uses which communication protocol:

  1. WiFi Module (ESP8266 ESP-01) uses Serial communication.
  2. RTC (Real Time Clock - DS1307) uses I²C communication.
  3. RFID Reader (RC522) uses SPI communication.
  4. SD Card Module also uses SPI communication.

Now, the Arduino UNO supports One I²C, One SPI and One Serial (by default) communication port.

So, you can easily connect your Wifi and RTC modules.

Now, actual problem is: "How to access multiple SPI interfaces on Arduino" (and that is a solved problem).

Hope it helps and you don't have to buy an Arduino MEGA.

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