Note: This tutorial could be outdated, please go here for a more current version.

Introduction

Like every phone, the GSM module on your Arduino MKR GSM 1400 can recognize DTMF tones. These are the tones that you can hear whenever you press a key on your phone's keyboard during a call.

How It Works

The operating principle of this tutorial is very simple: every time a phone call is received, the board answers the call and waits for a DTMF tone. When the tone is pressed, the board parses it, prints it on the serial monitor, and changes the LEDs color according to the pressed button.

Hardware Connections

As you can see from the breadboard layout, a transistor is present between the Arduino board and the NeoPixel input. This is placed since the MKR GSM 1400 operates at 3.3V while the NeoPixel works at 5V. The transistor is used as a voltage translator. In the layout, there is also a single NeoPixel placed instead of the ring just for the sake of simplicity.

Setup

The setup to use this code is very simple. You just have to:

Plug the antenna into the board

Plug a micro SIM card into your board

Connect the LEDs as shown in the scheme

Plug the battery into the board

Plug the micro USB cable and connect it to your PC

Load the code on the board using the Arduino Java or Web IDE

Open the serial monitor

Call the board and enjoy pressing buttons on your keyboard!

EXPANDED TECHNICAL DETAILS

Global DTMF Telecommand Hub

This advanced cellular project allows you to control physical hardware from any telephone in the world using standard Dual-Tone Multi-Frequency (DTMF) tones.

Cellular Audio Stream Decoding: The MKR GSM 1400 established a voice call with the user. The Arduino then captures the audio stream and uses a software-based FFT or a hardware DTMF decoder to identify the "Keypresses" from the caller's phone.
Remote Action Mapping: Every key (0-9, *, #) is mapped to a specific Arduino action—such as "Toggle Gate," "Check Battery," or "Reset System"—providing an internet-free, global remote control.

Security

Caller ID White-Listing: Includes a security layer that only accepts DTMF commands from pre-authorized phone numbers stored in the MKR's secure memory.

title: "Arduino MKR GSM 1400 and DTMF" description: "This tutorial shows how to use the Arduino MKR GSM 1400's DTMF feature to have a direct interaction with your phone." author: "Arduino_Genuino" category: "Internet of Things, BT & Wireless" tags: - "iot" - "internet of things" views: 27571 likes: 25 price: 4500 difficulty: "Easy" components: - "1x Arduino MKR GSM 1400" - "2x Resistor 10k ohm" - "1x Jumper wires (generic)" - "1x 3.7 V LiPo Battery" - "1x NeoPixel Ring: WS2812 5050 RGB LED" - "1x 2N7000" - "1x Breadboard (generic)" tools: [] apps: - "1x Arduino IDE" - "1x Arduino Web Editor" downloadableFiles: - "https://create.arduino.cc/editor/Arduino_Genuino/8e87bd19-988e-4082-a2be-d0525519d369/preview" - "https://create.arduino.cc/editor/Arduino_Genuino/8e87bd19-988e-4082-a2be-d0525519d369/preview" documentationLinks: [] passwordHash: "05ea792909ea7a91cf3eb4c8f8a6808729e33cee6563bd96e5259bfdd7d92352" encryptedPayload: "U2FsdGVkX1+StIS5/dTVMQpp+70TxEtD+0RmwNYPyghMHVMWAcl6sDScNC+vXhNs0ATi2UsYx9uPzwavFsnyIjLR1YOUGHwX7FS8z5NZFwg79AIAVe+AQpNHmepOcLSn" seoDescription: "Learn how to use Arduino MKR GSM 1400 DTMF feature for direct phone interaction." videoLinks: [] heroImage: "https://cdn.jsdelivr.net/gh/bigboxthailand/arduino-assets@main/images/projects/arduino-mkr-gsm-1400-and-dtmf-d1b395_cover.jpg" lang: "en"