Demoboard specifically designed to exploit the full potential of the MP3 / WAV audio player module DF Robot (DFR0299). The demoboard has 20 buttons that allow you to manage the files stored on an SD card (max. 32 GB - not included) inserted into the player module slot; USB interface that allows it to read data from a Pen Drive, DC power plug, jack for audio output, pin strip to enter a serial / USB converter (not included) to interface to a PC in order to transfer files MP3 to be played. Since this is a demoboard all contacts have been extended to the outside, including the TX and RX dell'UART internal to the module, working base to 9,600 bps. The entire circuit is powered at constant voltage of value between 9 and 12 Vdc.

Note: MP3 modulate the DFR0299 code and the USB-serial converter FT782M code are not included (see related products).

This project comes in  kit . Some components have to be soldered to the included PCB.

To allow the reading of more buttons was adopted a ruse that makes the A / D converter internal use in microcontroller assigned to ADKEY1 and ADKEY2 lines. This solution was adopted because otherwise the reading of the buttons 20 provided would require as many feet.

The buttons are divided into functional groups: those that activate the direct playback of the tracks (in this case in the control buttons is provided for playback of 14 audio files) and those which control the mode of operation; the former are 01 to 14 and pressing one of them is executed automatically playing songs that are found in the respective position in the mass storage media used or default.

Then the pressure of 01 makes directly play the first track, that of the second 02 and so on until the track 14. It should be noted that the fourteen keys related to memory segments in which the same number of tracks are stored have two
activation modes: a short press starts playing while a long press determines the repetition of the song from the beginning.
Play Mode decides the playback mode, or if you play the current track to the end, or go immediately to the selected one (interrupt / not interrupted mode); at every press of the button reverses the mode; U / SD / SPI button
manually set the selection of the source from which to read the files for playback (U / TF / SPI / Sleep):
Each press passes, in order, from USB to SD card to SPI, then the third press goes into Sleep Mode and then start again..The third function key, or Loop, toggles between the single play mode to cyclical: in the first case the selected track using the buttons 01 to 14 is played only once for each tap, while in the second (cyclical) the end begins over again indefinitely, or until it cuts off power to the circuit, the Loop button is pressed again, or working on the Pause / Play button.

The latter serves, in fact, to pause the current playback or to resume if it is paused; This applies whether the single play (one-shot) has been selected as the cyclical and does not alter the settings made with the previous buttons.
Next / Vol + button also has this dual functions:
pressed shortly blows up, while playing a song, to that of the next; equals, in this case, the skip.

If held longer, turn up the volume of voice (that is, the level of the audio signal supplied to the amplifier outputs and integrated in the module) continuously until it is released Similarly, the Prev / Vol- button (the fifth function key) if pressed briefly blasts playback from that of the current song (selected by 01/14) to the previous track (for example if the player is playing track 5 starts playing 4) and when it is pressed for a long time lowered the volume d 'listening gradually until it is released.
About the listening volume, note that startup automatically part by higher volume, then go adjusted via keys (more precisely, you will have to intervene in Prev / Vol-) to suit your needs.

• Power supply: 9 ÷ 12 Vdc
• Maximum current consumption: 500 mA
• pushbutton control
• Supported file formats: MP3 and WAV
• playable tracks: 14
• Data source: microSD and USB
• Automatic or manual selection of the data source
• Speaker output 3 watts mono into 8 ohms