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SOMO 14D (WTV020-SD-16P) and MDfly MOL-AU5121 (Tenda TDB380) sound module comparison

The 4D System's SOMO-4D and the MDfly AU5121S are sound playback modules that allow you to add audio to your projects. I've used both and find both are excellent in terms of sound quality vs. price point. Each one is slightly different and has their good and bad points. I will attempt to give the reader a summary of each and provide information that I had to travel the web for to compile myself. Although anyone can find the same info I thought it handy to provide it in one tidy place.

It should be mentioned that both modules sometimes exhibit problems with SD card compatibility. It often shows itself in the form of being unable to playback certain tracks or a track not playing completely. There are people on the web that have tested cards for compatibility but I found it difficult to find these exact cards to buy. It seems trial and error is almost inevitably the end result. Just consider this nuance during your testing.

Both modules will operate like a normal music player: Play, pause, stop, next, volume, etc. Both also have a BUSY line that indicates when a track is playing by holding the pin high or low until the track is finished playing. The notable differences between the two players are covered below.

4D System's SOMO-4D Sound Module

  • uses a micro SD card of up to 2GB
  • plays audio files in the .AD4 format.
  • 2.7V - 3.6V power supply
  • mono output for amplification and a separate 16-bit PWM output that can power a small speaker
  • two-wire data communications
  • 512 file maximum

There is also a clone of this called the WTV020-SD-16P. Both of the modules use the same decoder chip. The chip has different "modes" that are programmed one time only, usually when purchased, and it cannot be changed. Most people will want to control the module with a microcontroller. In this case you need one programmed in "serial mode." There is also "MP3 mode," "loop mode," and two "key modes," None will communicate in the two-wire serial protocol. This is important to note upon purchase.

The two-wire serial communication is similar to a very slow SPI interface. It uses a clock and data line to send 16-bit command codes to the module. It's not incredibly difficult to figure out but for a beginner unfamiliar with bit-banging or I2C the coding might be a hurdle to overcome.

The .AD4 audio format that is used is not that common. Included below are two conveter programs with instructions that will convert WAV files to the AD4 format(and one converter supports MP3s as well). I've read accounts of people having success with WAV files of certain formats. I can neither confirm nor deny that they will work.

Essentially the information provided for the two modules are the same but they are presented differently. For that reason I've attached both the datasheed for the SOMO-14D as well as the one found with the clone from the Far East.

MDfly MOL-AU5121 MP3 player

  • uses a standard sized SD card of 32MB-2GB
  • plays audio files in the .MP3 format.
  • 6V-12V power supply (can be used at 5V)
  • stereo output for amplification or use on headphones
  • one-wire serial and parallel communications
  • can store 199 audio files in each of 15 subfolders

This module is also known as the Tenda TDB380. It is easier to communicate with compared to the SOMO-14D. You can use the 8-bit parallel interface but most will probably want to use the one-wire serial option. All commands are composed of just a single byte. The command byte is sent to the module at 4800 baud. That's it. Simple.

Whereas the SOMO-14D has an output that can produce audible sound from a speaker in a quiet environment, this one will require an amplifier unless use with headphones is acceptable.

The datasheet provided by MDfly has the basic information to get you going but isn't a very detailed datasheet. For those that need to know more details I've also provided the manual that Tenda has for the TDB380.


And now for the all-important "summary-of-the-author's-pros-and-cons" section:


SOMO-14D/WTV020 module

Pros: Small, cheap, uses micro cards, doesn't need an amp for small speaker.

Cons: Can be bought in the "wrong mode," mono output, takes forever if ordered from the far east, strange communication syntax, requires three I/O pins for real-life communication, needs diodes to bring down 5V inputs.


MDfly/Tenda module

Pros: No file conversion needed for MP3s, wide supply voltage, stereo output, truly a two-wire interface (SER and BUSY), easy command structure, massive file storage potential.

Cons: Large, uses large SD cards, did I mention large? Breadboard-hungry edge mounted headers, needs an amplifer for even a small speaker, slightly higher price. 


4D-SOMO-Tool.zip773.17 KB
SOMO_Audio_Converter_User_Guide-rev3.pdf187.96 KB
AD4CONVERTER_instructions.txt467 bytes
SOMO-14D-DS-rev3.pdf1.02 MB
WTV020_manual_V1.3.pdf455.75 KB
AU5121Sspec.pdf83.07 KB
TDB380_datasheet_V21.0_.pdf1.04 MB

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Ok, so I wired up my WTV020-SD-16P. At first I was having no luck getting sound out of it (beyond some "clicks"). Then I decided to take drastic measures trying to assert if the problem really was the "widely" known pickiness regarding SD cards. Thus I booted into windows and decided to try this SD card formatting tool that Bajdi had recommended me earlier. Rebooted into linux, and voilá... it is now working \o/

To control the module I'm using the arduino library that can be found here.



Good to hear/see you have managed to succeed in your efforts.

Audacity is capable of generating the AD4 files as well. All you need to do is convert them to mono 16k sampling and then export them as other uncompressed files and then in the options select Microsoft WAV as the header and Microsoft ADPCM as the encoding.

The sample I sent to him came out like white noise give or take. I will take another stab at it and see what we can come up with.

if they both use the same chip, one would think they should both be able to play wav files.