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Arduino Mega Box Music Player By Bao Smith Combine an Arduino MP3 player shield with the Altronics Mega Box, along with our software, to make a neat little music or audio player with endless possibilities. W e introduced the Altronics Mega Box kit in the December 2017 issue of Silicon Chip. It allows you to give your Arduino projects a much more professional appearance and provides many convenient functions. In that article, we mentioned that one possible use of the Mega Box would be to combine it with the VS1053 MP3 player shield, which we used in our Music Player project in July 2017 (see siliconchip.com.au/ Article/10722). That project was presented as a collection of boards and modules wired together. That’s pretty typical for your average Arduino project but we wouldn’t say that it gives a finished product that you can use every day. Well, that changes now because we’ve revamped the software to take advantage of the facilities provided by the Mega Box. By using the Mega Box, rather than just stacking the MP3 Player shield on an Arduino Uno, we can use a universal infrared remote control rather than the 4x4 keypad. That provides several benefits including a larger number of keys and siliconchip.com.au buttons, more intuitive user interface and the fact that you can carry the remote around with you. We’ve also changed the software so that you can use at least two of the four illuminated pushbuttons on the front panel to control the player. If you want to use the other two and the rotary encoder, you’ll need to use an Arduino Mega instead of the Uno as the Uno just doesn’t have enough free I/O pins. The software will auto-detect if you are using a Mega board and allow use of the extra front panel controls. This version of the Music Player also incorporates the changes we’ve made to the software since the July 2017 article, to fix some issues reported by constructors. This includes a fix for dropouts during recording and an improved menu system. Now, having mentioned how well the Mega Box suits this project, we should add some caveats. The Mega Box is supplied with a 16x2 LCD, which is smaller than the 4-line unit that we used in the original version of the project. And since the supplied LCD has a slightly non-standard pinout, you Celebrating 30 Years can’t easily attach an I2C translator module (but it isn’t impossible if you want to save four pins). So we need to use the LCD in 4-bit data transfer mode which requires the use of six of the Arduino’s I/O pins (plus an additional PWM pin if you want to control the backlight). Also, the way the MP3 player shield is designed means that the headphone and microphone sockets face into the box, rather than out through the hole provided near the rear of the shield mounting point. That means you will need to drill a couple of holes to mount chassis sockets and wire them up to plugs which go into the shield sockets. Alternatively, you can run two 3.5mm male-female extension leads from the shield to the rear of the case. As an alternative, you can use the SparkFun version of this shield (www. sparkfun.com/products/12660). It has the same pin layout but has the headphone jack pointed at the rear, but you will need to solder your own microphone input socket onto the board. That shield is a bit more expensive than the version we used originally February 2018  83 but it’s also decidedly less dodgy, in that it uses a proper level translator between the 5V Arduino board and the 3.3V audio player IC. The infrared interface is now the main means of controlling the unit and while you could probably use just about any universal remote, we’ve designed it with the Altronics A1012 in mind (siliconchip.com.au/link/aaio). We’re using TV code 170 (see supplied instructions for how to set that). You can use this to operate the unit from up to five metres away. The A1012 TV code 170 button codes are shown in Table 1. If you want to use a different remote control, you will need to set it to produce Philips RC5 codes and then change the “#define” lines at the top of the Arduino code to the appropriate code numbers to suit your remote. The best way to check what commands your remote sends are by running the sample Mega Box program that Altronics have on their website and read the values off the serial console in the Arduino IDE: siliconchip. com.au/link/aais Assembling the project is fairly simple if you’ve already built the Mega Box. If you haven’t, see our December 2017 article for the details (siliconchip.com.au/Article/10902) and/or follow the instructions supplied with the kit. The main difference will be in how you want to handle audio input and output. What we did was mount two 3.5mm stereo sockets in a convenient location on the front or rear panel (eg, above S1-S4, or to the left of the rotary encoder); a 6mm drill bit should do. After this, solder an adequate length – depending on the location of the sockets – of stereo shielded cable to their pins. You can just use one cable and cut it in two and then strip the outer sheath. Next, separate the individual leads and strip the ends of the red and white leads before soldering them to the connector; white to tip, red to ring and the shield wires to ground. Be careful since some sockets are switched and will have more than three pins; you will need to plug an audio cable in and use a DMM set on continuity mode to figure out which is the tip (left), ring (right) and sleeve (ground) connections. Wire these up to the two line plugs using the same pin assignments, so that you end up with what are essentially two extension leads that can then be plugged into the MP3 Player shield. We also recommend that you add a 3.6V 1W zener diode between the 3.3V line (cathode) and ground (anode). The easiest place to fit this is between CON3 and CON5 which are located between the Arduino and the shield on the Mega Box board (these may be labelled U3 and U5 on the PCB). This is not necessary if you’re using the SparkFun MP3 Player shield. The reason it’s required is that the Geeetech MP3 Player shield’s lack of level shifting circuitry causes the Arduino output pins to “pump up” the 3.3V supply when they go high and this can cause a buzzing in recorded audio. The zener diode helps to prevent the loss of regulation on the 3.3V rail due to this pumping action. Note that there’s a small risk that the diode could overheat; we’re counting on the fact that its voltage “knee” is just above the normal voltage of the 3.3V rail and so it will only conduct a small amount of current (milliamps) at 3.3V. But it’s possible your diode could have a low knee voltage or your 3.3V We’ve used a 3.5mm switched stereo audio socket (enlarged). You’ll need to use a DMM on continuity mode to determine which lead is the tip (white; left), ring (red; right) and ground. A close-up of the 3.6V zener diode inserted with cathode to the 3.3V line and anode to GND. Assembly Table 1: IR codes Button Standby (on/off) Mute Buttons 0-9 Channel up/down Volume up/down Up/down Right/left OK Teletext Page hold TV/Video Pause Exit Rewind Play Fast forward Stop 84 Silicon Chip Hex code (0x) 0C 0D 00-09 20/21 10/11 12/13 14/15 23 3C 29 3F 3D 0B 37 32 34 36 Celebrating 30 Years siliconchip.com.au regulator could have a slightly higher output than typical. So after fitting it, power up the Arduino and make sure it isn’t getting too hot. Wiring it up Now refer to Table 2 to see which connections you need to make using jumper leads. Some of the connections can only be used with an Arduino Mega, as indicated in the table, so if you’re using the Uno you will have to leave them out and their related functions will not be available. Since the pushbuttons are wired with pull-up resistors, the pins connected to the pushbuttons are read as high by default and low when pressed. The button’s NO connection should be wired to +5V by placing jumpers on JP1. Note that Arduino pins D2, D6, D7, D8 & D9 are exclusively being used by the MP3 Player shield and cannot be used for anything else, while D11-13 can be used with other SPI devices. This leaves D0 (receive), D1 (transmit), D3, D4 and D10 (slave select). Generally, D0 and D1 should not be used as this would interfere with the serial console, nor D10 as that is driven by the Arduino SPI unit. Once all connections have been made, the Arduino sketch software can be loaded. It’s available for download from the Silicon Chip website (free for subscribers, and it will be bundled with the July 2017 software). You will also need to load your audio files (and two required patch files) onto the root directory of a properly formatted microSD card (FAT16 or FAT32) and insert this into the socket on the player module. If you don’t already have the latest version of the Arduino IDE, download it from www.arduino.cc/en/Main/ Software and install it. The next step is to install the required libraries, which are supplied in the download package along with the sketch. Use the Tools → Libraries → Add .ZIP Library menu option to install each one in turn. Then open up the sketch file, make sure the correct COM port is selected in the Tools menu, and then select the Upload option (CTRL+U in Windows). Check the bottom of the IDE window to make sure the upload was successful. Next, adjust LCD contrast potentiometer VR1 so that you can comfortably read the text on the LCD screen. If you don’t see any text, check that the SD card is properly connected and try connecting the LCD backlight interface to the +5V line to make sure the screen isn’t too dim. By default, the software uses the line in connection when recording, which means you will need an external microphone. You can alter the software to use the Geeetech on-board electret microphone by removing the line “#define USE_LINEIN 1”, but the resulting quality is quite poor. Remote control functions You should find the infrared remote control buttons to be fairly straightforward. The arrow keys are used to navigate the menus with the OK button used to select the current choice. Shown above are the flying lead connections that need to be made to use the project with an Arduino Uno. Take note of the jumpers for S1 & S2. If you have a spare PWM pin, the backlight can be controlled using that instead of the yellow lead going to 5V. The audio sockets don’t need to be placed where we have as it does interfere with the header for the Arduino Mega. Other good locations include above the four pushbuttons or on the back panel above the five relays. siliconchip.com.au Celebrating 30 Years February 2018  85 Table 2: Lead Connections Component 16x2 LCD Infrared Remote Pushbuttons Rotary Encoder To Pin RS A0 EN A1 D4 A2 D5 A3 D6 A4 D7 A5 Backlight 5V IR interface D3 S1 COM# D4 S2 COM# D5 S3 COM^# D14 S3 COM^# D15 Encoder interface A^ D16 Encoder interface B^ D17 Alternatively, you can press a button on the numeric keypad to directly choose the respective menu option (as shown on the LCD). When playing an audio file, the up/ down arrow keys and channel up/ down will go to the previous or next file respectively. The OK, play and pause can be used to pause or play the current file. Volume up/down will alter the volume, the mute button will toggle mute, fast-forward and fast-rewind will speed up or slow down playback, rewind will restart the current song from the beginning and the back/exit/ return button on the remote will end playback. When choosing the menu option “play track number”, you use the numeric buttons on the remote to enter a specific three-digit track number to play. The left/right arrows can then be used to select which file format to play from (both MP3 and OGG are supported). When recording, you will need to select a file number to record to and the process is the same. Or you can simply press OK to record in a sequential order, ergo, record00.ogg, 01, 02… Using Bluetooth speakers If you want to use Bluetooth speakers, headphones or some other Bluetooth audio receiving device, all you 86 Silicon Chip Parts List Lead 1 Inventa Mega Box kit (Altronics Cat K9670) 1 Arduino Mega (recommended) or Uno (or compatible) 1 VS1053b based MP3 Player shield (Silicon Chip Online Shop Cat SC4315 [Geeetech] or SparkFun version [see text]) 1 Altronics A1012 universal remote control 4 jumper shunts (2 if using the Uno) 2 3.5mm stereo chassis-mount sockets 2 3.5mm stereo line plugs (Altronics Cat P0030) 1 1m length stereo shielded audio cable 1 USB Type A to Type B (full size) cable 1 USB charger or other USB power supply 16 150mm long male-male jumper leads (minimum 11) 1 3.6V 1W zener diode 1 Bluetooth audio transmitter (optional) 1 PCB-mount Type-A USB socket (for Bluetooth audio transmitter) ^ only available when using Arduino Mega board # place a jumper on JP1 With an Arduino Mega these pins MUST be connected in parallel: 11 → 51, 12 → 50, 13 → 52 for the SD card to work. need to do is buy a Bluetooth audio transmitter. They’re quite cheap and compact. Here is one we’ve purchased and used quite successfully: siliconchip.com. au/link/aair It can actually be used as a transmitter or receiver; dedicated transmitters cost around the same price (about $20). We found the audio quality to be reasonable. It comes with a short 3.5mm plugto-plug cable so it can be plugged straight into the audio output on the MP3 Player module. It’s also supplied with a short USB cable to power it, with a Type-A plug on the end. You will need to solder a PCB-mount Type-A socket to the prototyping area on the Mega Box and wire up its +5V and GND pins to supply points on the Mega Box board. Fig.1 shows the connections required for the USB socket; the Dand D+ connections do not need to be made. Be careful since reverse polarity may destroy the Bluetooth transmitter. You will then need to attach the Fig.1: expanded view of a USB Type-A socket showing the required connections. Celebrating 30 Years transmitter inside the case somehow (eg, double-sided tape or silicone sealant) and then wire it to the socket with the supplied USB power cable. If you’re clever, you could drill a hole into the case giving you access to the button on the transmitter unit, which you need to press before you can pair it with your receiver. However, given that pairing is something you only need to do when connecting it to a new receiver, that may not be necessary. What can it play? As mentioned in the previous article in July 2017, assuming you have the correct patch file located in the root directory of the SD card, the player can play these formats/containers: Ogg Vorbis, MP1, MP2, MP3, AAC, WMA, FLAC, WAV and MIDI This should cover most of the audio file formats that you will commonly encounter. The VS1053b chip is able to record in the following file formats: Ogg Vorbis, PCM and ADPCM. However, the software is only programmed to record in the Ogg Vorbis compressed format. A list of individual bitrates which are supported by the IC for each file format can be found under section 8 in the VS1053 datasheet: www.vlsi.fi/ fileadmin/datasheets/vs1053.pdf SC siliconchip.com.au