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Using Cheap Asian Electronic Modules Part 21: by Jim Rowe A stamp sized digital audio player The DFPlayer Mini is a low-cost digital audio player module. It's available from popular internet suppliers, including Banggood, as well as from marketplaces like eBay and AliExpress, for as low as a few dollars, including postage. Despite its size and price, it can do a lot! This is a very flexible module with a great many features. I was very impressed after trying the module out for myself. One of the best things about it is that it plays several different audio file formats, including MP3, WMA and WAV, in mono or stereo, and it can read those files off either a microSD card or USB flash drive with a capacity up to 32GB in either case. But it has a lot of other features, so let's take a look at the hardware involved and how to drive it. What's inside the module Circuit diagrams for the DFPlayer Mini module are hard to find but an examination of the module reveals that it's based on two ICs: a YX5200-24SS (IC1) which does most of the work and a smaller 8002 audio amplifier chip (IC2). While data sheets for both devices are available, the sheet for the YX5200- 24SS is almost entirely in Chinese. But I was able to glean enough info to draw the module's internal block diagram, shown in Fig.1. The YX-5200 chip is the module's brains. Inside it, there's a 16-bit MCU (micrcontroller), an analog DSP (digital signal processor), EPROM and flash memory, a 24-bit stereo DAC (digitalto-analog converter), a serial UART for communication with an external MCU and ports to communicate with a microSD card or a USB thumb drive. All this in a compact 24-pin SSOP (SMD) package – it's virtually a complete digital audio system on a chip! The YX-5200 chip can play back MP3, WMA and WAV files at sampling rates of 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz or 48kHz. It can handle files on either microSD (“TransFlash” or TF) cards or USB thumb drives with capacities up to 32GB, formatted with a FAT16 or FAT32 file system. You can store up to 45 hours of CD-quality WAV files on a 32GB card/drive, or about 23 days worth of 128kbit MP3 files. The 24-bit stereo DAC in the YX5200 is claimed to provide a dynamic range of 90dB, with a signal-to-noise ratio (SNR) of 85dB. That isn't exactly hifi but it isn't too bad either. The built-in MCU and DSP combine to provide features like audio gain adjustment over 31 levels and the ability to select one of six playback tonal equalisation settings. You can also select the playback mode (normal/repeat/folder repeat/ single repeat/random) and the playback source (USB drive, microSD card or a couple of other options). It also provides a BUSY logic output signal which is at logic low level (<800mV) when playing a file, rising to logic high (~3.5V) when playback stops. Turning to IC2, its operation is quite straightforward. Housed in an 8-pin SOIC package, it's basically just a low-power audio amplifier with a few extras. Running from 5V, it can deliver up to 2W into a 4W loudspeaker load with 10% total harmonic distortion (THD+N), or 1.5W into an 8W load with 1% THD+N. Views of the top (left) and bottom of the DFPlayer Mini module with a microSD card inserted. It is shown at close to double life size for clarity. 74 Silicon Chip Australia’s electronics magazine siliconchip.com.au Features & Specifications R Just 21 x 21 x 12mm including microSD card socket and pin headers R Plays MP3, WMA and WAV audio files (4.3 filenames) R 24-bit stereo DAC R Built-in 2W mono bridge-mode amplifier R Plays files from microSD cards or USB flash drives (up to 32GB) R Multiple control options, from as few as four pushbutton switches to full serial mode control from a microcontroller such as an Arduino or Micromite R Line-level stereo outputs which can also drive headphones R Six playback equalisation options: Normal (flat), Pop, Rock, Jazz, Classical and Bass R Programmable playback volume in 31 steps (0-30) R Runs from a 3.3-5.2V supply, drawing 25mA when idle or 200250mA during playback It provides a push-pull (bridged) output and no output coupling capacitors, snubber network or bootstrap capacitors are needed. It's also unity-gain stable, has an externally programmable gain and includes circuitry to suppress clicks and plops during power on/off. As you can see from Fig.1, the DFPlayer Mini module makes good use of the many features provided by both ICs. As well as providing all of the main control inputs needed by IC1, it also features a microSD card socket on the top of the module connected directly to IC1. The latter's BUSY signal output is brought out to a pin and also drives LED1, a tiny blue SMD LED. The left and right channel outputs from the YX5200's DAC are also brought out for use in driving either headphones or an external amplifier, in addition to being mixed together and fed into IC2 to drive a speaker directly. No socket is provided for plugging in a USB thumb drive – just a couple of pins identified as USB- and USB+. I couldn't find any information on the use of these pins anywhere in the commonly available data sheets for the DFPlayer Mini module but I guessed that these could be connected to the D- and D+ signal lines of a USB socket, and as you will see later, I was right. Fig.1: block diagram of the DFPlayer Mini audio player module. The total current requirement is around 25mA when idle, rising to around 200-250mA during playback. The module can be used as a selfcontained audio player controlled merely using four SPST pushbutton switches, connected as shown in Fig.3. Alternatively, a much larger array of 20 pushbuttons can be connected as shown in Fig.4. Otherwise, its operation can be controlled entirely from an Arduino, a Micromite or many other kinds of microcontroller, using the UART serial port lines at pins 2 (RX) and 3 (TX), along with the BUSY signal from pin 16. This configuration is shown in Figs.5 & 6. The rest of the connections are to make use of the module's extra features. For example, you can use it to play files from a USB thumb drive by connecting up a Type A USB socket as shown at the top right of Fig.2, with pin 1 connected to the +5V supply, pins 2 and 3 to pins 15 (USB-) and 14 (USB+) of the module, and pin 4 to the module ground (pins 7 or 10). The dashed connections to pins 4 (DAC_R) and 5 (DAC_L) of the module show how it can be used to drive either stereo headphones or line-level outputs to an external stereo amplifier or hifi system. Returning now to Fig.3, which shows the simple four-pushbutton control scheme, S1 and S2 have dual functions in this mode. A short press is used to move to the previous track (S1) or the next track (S2), while a longer press either decreases (S1) or increases (S2) the volume. S3 and S4 each have only single functions, to start playing the first track (S3), or the fifth track (S4). The more complex pushbutton con- Putting it to use Fig.2 shows how to wire up the DFPlayer Mini module. The speaker (if used) connects directly between the SPK_1 and SPK_2 pins (6 and 8) while the module's power supply (3.35.2V DC) is fed to pin 1 (Vcc) and pins 7/10 (GND). siliconchip.com.au Fig.2: This shows how to connect the audio player module for playback to a speaker, headphones or other audio devices via the level outputs. Australia’s electronics magazine December 2018  75 Press S1: previous track Hold S1: increase volume Press S2: next track Hold S2: decrease volume Press S3: play first track Press S4: play fifth track Fig.3: the simplest method of controlling the DFPlayer module is by using four pushbutton switches. Track 5 is equivalent to 005.mp3 (four characters at most for a filename, three for the extension); folders are named 01 to 99. trol arrangement of Fig.4 is a bit more tricky. To allow twenty pushbuttons to be connected using just two pins, each of the ten pushbuttons in a given “bank” has a different resistor value connected in series. The chip then measures the current sunk from pin 12 or 13 when a button is pressed and depending on what range it is in, it knows which button was pressed. In this mode, most of the extra switches (S7 - S20) are simply used to allow direct selection of tracks to play. Switches S5 and S6 basically duplicate the actions of S1 and S2 in Fig.3, while the first four switches (S1 - S4) allow control over the playback mode (single track/continuous), playback source (USB/SD/SPI/SLEEP), enable loop all mode and provide the pause/ play function. Controlling it with a micro Hooking the DFPlayer Mini up to a microcontroller is simple, thanks to the module's built-in UART serial port. You just need to connect the module's RX input (pin 2) to the serial TX output of the micro and connect the module's TX output (pin 3) to the serial RX input of the micro. The GND of the module (pin 7 and/or 10) also needs to be connected to the micro's ground network. The module's UART is pre-programmed to communicate at 9600 baud, with the basic 8N1 protocol. It's also a good idea to link the module's BUSY output (pin 16) to a digital input on the micro so that the control program can tell whether the module is playing a file or has stopped. Arduino specifics Fig.5 shows the connections for controlling the module from an Arduino. It's powered from the Arduino's 5V supply, which is fed to its Vcc pin (pin 1). For serial communications, we're using Arduino digital I/O pins 10 and 11, which are driven by the SoftwareSerial library code. The D11 digital output is connected to the RX pin on the module via a 1kW series resistor. That's because the module inputs can handle a 3.3V signal while the Arduino pins have a 5V swing. The resistor limits the current into the module's RX pin to a reasonable level (less than 2mA) when D11 is driven high. The only other connection needed is between pin 16 of the module (BUSY) and D3 of the Arduino, for the reasons described above. For clarity, Fig.5 does not show a USB socket, headphone socket, line outputs etc, which were shown in Fig.2. But these can certainly be included if you need those functions. There are many different libraries and sketches on the internet which show how to drive the DFPlayer Mini from an Arduino, although some are a bit flakey and/or hard to understand. But one of the best is from the manufacturers themselves, DFRobot and is called “DFRobotDFPlayerMini1.0.3.zip”. It includes a set of exam- Fig.4: a more complex method for control involves 20 pushbuttons, each with a series resistor (except S10 & S20). S7-20 just allows playback of tracks 1-14 directly (holding the switch will cause it to repeat indefinitely), while the rest of the switches are for playback functionality with S5/6 identical to S1/2 in Fig,3. Switch functions: S1 – single track/continuous playback S2 – change playback source (USB/SD/SPI/sleep [none]) S3 – loops the current track S4 – pause/play 76 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.5: wiring diagram for the audio player module when connected to an Arduino. ple sketches and you will find a link to download it below. Driving it from a Micromite If you're one of the many Micromite enthusiasts, Fig.6 shows the basic connections needed to control the DFPlayer Mini module from a Micromite Backpack. The arrangement is very similar to that for the Arduino. The module's RX (2) and TX (3) pins are connected to pins 9 and 10 of the Micromite respectively, again with a 1kW series resistor in series with the line to the module's RX pin. Pins 9 and 10 of the Micromite are the TX and RX pins for the Micromite's COM2 serial port. The remaining connection is from the BUSY pin (16) of the module to pin 24 of the Micromite, again to provide a playing/not playing signal. And again, for clarity, Fig.6 leaves out any extra connections you may wish to make to the DFPlayer module, like those shown in Fig.2. I couldn't find any pre-existing Micromite programs to control a DFPlayer Mini, so I wrote one myself, after studying the YX5200-24SS data sheet and also some of the Arduino library files. The program is called “DFPlayerMini control program.bas” and it's available from the Silicon Chip website. It's designed to run on the LCD BackPack (see February 2016 [siliconchip. com.au/Article/9812] and May 2017 [siliconchip.com.au/Article/10652] issues); As you can see from the screen grab of the LCD touchscreen, the program gives you a set of six touch buttons labelled PLAY, PAUSE, PREV, NEXT, VOLUME (down) and VOLUME (up). Touching any of these buttons makes the Micromite send a command to the module to achieve the desired response, similarly to how the hardware switches shown in Fig.3 work. Now this MMBasic program is pretty simple but it should give you a good starting place for writing more elaborate programs yourself. With the technical information on the DFPlayer Mini module in this article, you should be able to get the module performing all kinds of impressive tricks! Handy links Module information and software: siliconchip.com.au/link/aald Software library and sketches: siliconchip.com.au/link/aale Documentation and Arduino library: siliconchip.com.au/link/aalf SC Above: screenshot of the MMBasic example program running on a Micromite. Fig.6 (right): wiring diagram of the audio player module connected to a Micromite. siliconchip.com.au Australia’s electronics magazine December 2018  77