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SOMO-II Arduino Library

An Arduino library to communicate with a SOMO-II module to play MP3 files.


Set up the required Serial object based on the pin connections you are using. Remember that the TX pin on the microcontroller board should be connected to the RX pin on the SOMO-II board, and vice-versa.

  RX (Arduino) ----------------- TX (SOMO-II)
  TX (Arduino) ----------------- RX (SOMO-II)

When connecting to arbitrary pins on the Arduino, you'll need to use SoftwareSerial to create a secondary serial connection. In your Arduino Sketch, include and construct both the SoftwareSerial and SOMO_II items:

#include <SoftwareSerial.h>
#include <SOMO_II.h>

#define RX_PIN 8  // connect to SOMO-II TX
#define TX_PIN 8  // connect to SOMO-II RX

// set up a new serial object
SoftwareSerial mySerial = SoftwareSerial(RX_PIN, TX_PIN);

SOMO_II mp3 = SOMO_II(mySerial);

Or, if the SOMO-II is connected to a spare hardware serial port:

#include <SOMO_II.h>
SOMO_II mp3 = SOMO_II(Serial1);

Start both the serial port at the required baud rate, and then call SOMO_II::begin() during the setup function:




This will start the SOMO-II module and set the volume to the mid-level.

Playing MP3 files

In it's simplest form, you can call playTrack(track_num) to play tracks based on the order they were copied onto the storage media, but if the tracks are arranged into numbered folders (eg. 001) and the files have preceding numbers (eg. 001file.mp3), then the playFile(folder_num, file_num) function is a little more useful.

To change the volume, there are volUp() and volDown() functions to step up or down the volume range (0–30) in increments of 1, or the setVol(volume_level) to set it to a specific value.

The functions are intended to be used with feedback() on (feedback(true)), currently the default, and they will then return a value based on if they are successful (SOMO_OK) or not, and will return the error code.