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By MAURO GRASSI An SD Card Music & Speech Recorder/Play This digital recorder stores WAV files on low-cost MMC/SD/ SDHC cards. It can be used as a jukebox, a sound effects player or an expandable “dicta-phone”. You can use it as a free-standing recorder or in conjunction with any Windows, Mac or Linux PC. 30  Silicon Chip siliconchip.com.au A universal IR remote is used to control the Digital Speech Recorder or you can use the on-board buttons. Recordings can be made direct to the memory card via a mic or line input or you can copy audio files onto the card from a PC. I N MAY 2005 and December 2007 we published two very popular solid-state voice recorder projects. The 2007 design was an improved version of the original project, employing the same voice recorder chip. These allowed you to record a number of short messages (up to about one minute of speech) and play them back at the touch of a button. The messages were stored in “analog EEPROM” cells in an analog 8-bit format. This project takes the message re- corder concept to a whole new level and employs a common SD memory card or MMC (multimedia card) for message storage. Depending on the size of the card, you can store and play back many hours of audio. We’ve also added infrared remote control and it can be used to play back any WAV file that you have downloaded or recorded on your PC. We are presenting this project in a very simple module format; it is just a PC board with an SD card socket, a er The unit works with all commonly-available MMC, SD and SDHC memory cards. You can copy files from a PC onto these cards via an MMC/SD/SDHC card reader like the one shown at bottom right. siliconchip.com.au 2-line LCD panel and eight pushbutton switches to select the audio files and other features. If you want to build the unit into a case, you can take the LCD panel off the board and separately mount it and the same goes for the switches and sockets. Compatible memory cards The compatible cards to use with this project are MMC (MultiMedia Card), SD (Secure Digital) and SDHC (Secure Digital High Capacity) cards. SD cards come in capacities up to 2GB. Beyond that, you will find SDHC cards with capacities from 4GB to 32GB. The current version of the standard does not specify cards with capacities higher than 32GB, although these will become common in the future. This project will work with most presently available cards. SD cards in particular have dropped in price dramatically and you can now pick up a 1GB SD card for less than $10. In operation, the unit can be run from either a 12V battery or a DC plugpack supply. It can drive stereo headphones or an external amplifier and loudspeakers. WAV file format The WAV file format from Microsoft can carry both compressed and August 2009  31 Parts List 1 PC board, code 01108091, 164 x 136mm 1 16 x 2 LCD module (Jaycar QP-5515, Altronics Z-7013) 1 1kΩ horizontal-mount trimpot (VR1) 1 10kΩ log 16mm dual-gang pot (VR2) 8 SPST 6mm tactile switches (S1-S8) (Jaycar SP-0601, Altronics S-1124) 1 DPDT PC-mount slide switch (S9) (Jaycar SS-0823, Altronics S-2060) 1 2.5mm PC-mount male DC connector (Jaycar PS-0520, Altronics P-0621A) 1 TO-220 mini heatsink (Jaycar HH-8502, Altronics H-0630) 1 10MHz crystal (X1) 1 SD surface mount card socket (Jaycar PS-0024) 3 3.5mm PC-mount stereo jack sockets (Jaycar PS-0133, Altronics P-0092) 1 infrared receiver module (IRD1) (Jaycar ZD-1952, Altronics Z-1611) 1 40-pin IC socket (to be cut) 1 28-pin IC socket (0.3-inch) 1 16-pin IC socket 2 8-pin IC sockets 12 M3 x 12mm Nylon screws (some to be cut) 8 M3 x 9mm tapped Nylon spacers 1 500mm 0.8mm-dia. length tinned copper (for links) 1 32-way machined pin socket strip 1 40-pin header strip 1 electret microphone insert (optional – see text) uncompressed audio but this speech recorder can only record and play back uncompressed WAV files. The samples are stored as 16-bit signed integers. The sampling rate of the encoded audio is stored in the WAV file header and is read by the recorder to vary the playback sampling speed. Both stereo and mono files can be played. When playing mono files, both output channels (L & R) carry identical signals. A stereo WAV file contains information for the left and right channels interleaved, meaning every second sample is taken for each channel. 32  Silicon Chip Semiconductors 1 dsPIC33FJ64GP802-I/SP microcontroller (IC1) programmed with 0110809A.hex (Altronics LCD) or 0110809J.hex (Jaycar LCD) 1 74HC595 8-bit shift register (IC2) 2 LM833N dual op amps (IC3-IC4) 8 1N4148 signal diodes (D1-D8) 1 1N4004 silicon diode (D9) 1 7809 3-terminal regulator (REG1) 1 7805 3-terminal regulator (REG2) 1 LM317T variable regulator (REG3) 1 3mm red LED (LED1) 1 3mm green LED (LED2) 1 3mm yellow LED (LED3) Capacitors 1 1000µF 16V electrolytic 2 470µF 25V electrolytic 3 470µF 16V electrolytic 1 220µF 16V electrolytic 5 100µF 16V electrolytic 3 10µF electrolytic 1 10µF tantalum 1 4.7µF electrolytic 2 220nF MKT polyester 2 150nF MKT polyester 3 100nF MKT polyester 5 100nF monolithic 2 18pF ceramic Resistors (0.25W, 1%) 1 220kΩ 3 1kΩ 7 100kΩ 1 180Ω (R2) 5 39kΩ 1 110Ω (R1) 2 27kΩ 7 100Ω 5 22kΩ 3 10Ω 4 10kΩ 1 0Ω (R3) 2 2.2kΩ (Note: 10Ω & 160Ω resistors may be required to adjust REG3). WAV files essentially store the PCM (Pulse Code Modulation) samples of the audio waveform. The sampling frequency is twice the highest reproducible frequency in the audio stream. Note that WAV files have a “.wav” file extension. Firmware overview The firmware is responsible for all the features of our new Digital Speech Recorder. When you play a file, the firmware reads the WAV header that stores the sampling rate of the audio file. It then sets up an interrupt to push data into the DACs (Digital-to-Analog Converters) in the microprocessor at the requested sampling rate from the memory card. When recording, data from the micro’s ADC (Analog-to-Digital Converter) is written to a WAV file on the memory card using double buffering. The audio buffer stores up to 10KB of audio samples and each sample is 16 bits. FAT files In this case, FAT does not stand for fat or obese! Instead, it stands for “File Allocation Table” and is a file management system that’s commonly used for hard disk drives and memory cards. This Digital Speech Recorder recognises the FAT/FAT32 file system, meaning you should be able to read the cards using any Windows, Mac or Linux box coupled to a card reader or by using a laptop PC with an inbuilt card reader. If you want more information on the FAT file system, refer to http:// en.wikipedia.org/wiki/File_Allocation_Table or to a host of other internet sites. If your memory card has a different file system on it, you will need to format the memory card first using a FAT/FAT32 system. Be sure to back up whatever was on the card before you do this, because the formatting process will erase everything that may be on the card. File sizes Because this project does not decode compressed audio files, the size of the WAV files used is rather large compared to common MP3 files or similar audio formats. A WAV file can be up to 10 times larger than an equivalent MP3 file at the 44.1kHz sampling rate. Unlike MP3, uncompressed WAV is a lossless encoding format. Using lower sampling rates can reduce file sizes but this will also reduce the audio quality and bandwidth. Because we are using cheap and readily available SD or MMC cards, we are not too concerned about the size of the files. Even at 40MB per 4-minute audio track, you can still store around 25 songs (or 100 minutes) of audio on a $10 1GB SD card. Circuit description Refer now to Fig.1 for the circuit details. As shown, it’s based around a powerful 16-bit DSP microconsiliconchip.com.au Using Audacity To Convert MP3 Files To WAV Files C ONVERTING MP3 FILES (and other compressed audio formats) to WAV files suitable for the Speech Recorder is easy using a program called “Audacity”. This excellent freeware program allows you to convert at different sampling rates and can also be used as a basic sound editor. Audacity can be downloaded from http://audacity.sourceforge.net/ download/. There are versions for Windows, Mac and Linux. Follow the on-screen prompts after executing the downloaded installation program. troller from Microchip, the dsPIC33FJ64GP802 (IC1). The reasons for choosing this microcontroller are fourfold. First, it is one of the first microcontrollers from Microchip to have an integrated stereo DAC (Digital-to-Analog Converter). Second, it is very fast, running at 40MIPS (Millions of Instructions Per Second). You need such speed when you are reading from a memory card in real time and dumping audio data onto the DACs! Third, it has enough on-board RAM and program memory to implement the features of this project and comes in a through-hole package which is easier to install than an SMD. And finally, it runs from a 3.3V supply which is compatible with the supply requirements for a typical memory card. IC1’s system clock is derived from a 10MHz crystal (X1) via a PLL (Phase Locked Loop) stage to derive a 40MHz instruction clock. The two accom­ panying ceramic 18pF capacitors provide the correct loading for the crystal. siliconchip.com.au As indicated, Audacity can open MP3 (and other compressed) files.You can then export them to WAV format and copy them to an MMC/SD/SDHC card for use with this unit. The first step in the conversion is to select the required sampling rate. This is a compromise between audio quality and the size of the file. The higher the sampling rate selected, the higher the audio quality but the bigger the file size. Having selected the sampling rate, it’s then just a matter of clicking “File” In operation, the microcontroller is responsible for implementing the hardware layer to read and write sectors to the MMC/SD/SDHC card. This low-level layer is called by higher layers that implement a FAT/FAT32 file system. The result is that we can read and write files. The SPI (Serial Peripheral Interface) outputs of the microcontroller connect to the SD card and to IC2, a 74HC595 8-bit shift register that’s used to drive the LCD module. This shift register is used as a “port expander” because there are simply not enough output pins on the microcontroller. The output of the shift register is also used to scan the eight on-board tactile switches, S1-S8. These are connected via diodes D1-D8 which effectively form a wired AND gate and they are active low. The microcontroller can detect a switch press by loading the shift register with the values 0xFE, 0xFD, 0xFB, 0xF7 and so on, up to 0x7F (one 0 bit). Note that the E (enable) line to the and then selecting the “Export As WAV...” option. There is no reason to choose a sampling rate higher than 44.1kHz, as this is high enough to encompass the whole of the audio spectrum (remember that the sampling rate will be double the highest reproducible frequency and that the audio spectrum reaches up to about 22kHz). Having converted the files to WAV files, it’s then just a matter of copying them from the PC to the memory card via a card reader. LCD module is kept low during this scan, so as not to affect the contents of the display. Remote control The speech recorder and audio player can also be operated using a remote control. The infrared signals are amplified, filtered and demodulated by an infrared module (IRD1). Its supply is decoupled using a 10Ω resistor and 10µF electrolytic capacitor. The data line passes through a voltage divider consisting of two 27kΩ resistors to pin 14 (RB5) of IC1. Note that the infrared module works from a +5V rail whereas the microcontroller decoding the signal runs from a 3.3V rail. The purpose of the voltage divider is to roughly halve the signal level from the module so that it can be used with a 3.3V device. SPI mode As noted above, the SPI peripheral on the microcontroller is used to drive the LCD and scan the tactile switches. August 2009  33 +9V 10 +5V 10 F LED1 LED2 LED3 A A A  K 100nF 100nF 1k   K 100 +3.3V 2.2k K 100 1 100 MCLR 11 7 6 RB4 RB3 RB2 13 Vdd 39k 4 28 AVdd 22 RP11 21 RP10 18 RP9 17 RP8 Vdd 7 Dout 5 CLK 2 Din 1 CS 3 Vss1 6 10 IRD1 (MMC/SD/SDHC MEMORY CARD SOCKET) 3 27k 1  14 27k 2 RB5 IC1 dsPIC33FJ 64GP802-I/SP +3.3Vf RB1 RB0 100 F 39k 100 MIC IN 4 +9Vf 2 100nF 5 39k 100 F 2.2k Vss2 CON1 +9V 2x 100k 3 10 100nF X1 10MHz 8 3 2 IC3a 1 150nF 18pF 18pF 9 AN0 RA4 AN1 12 DACRp 23 OSCo DACLp OSCin Vss 8 25 Vdd 20 CORE AVss Vss 19 27 10 F TANT 39k 220k 100k 1k 4.7 F LINE IN 100nF 5 6 IC3b 4 7 150nF IC3, IC4: LM833N 39k 100k 100k 22k 100nF IRD1 LEDS SC 2009 DIGITAL AUDIO RECORDER/PLAYER K A 1 3 2 Fig.1: the circuit is based on a dsPIC33-FJ64GP802 microcontroller and a 16 x 2 LCD module. The micro scans the switch inputs via shift register IC2, drives the memory card, decodes the signals from the infrared receiver module (IRD1), writes to the LCD module and performs the ADC conversions on the analog inputs. 34  Silicon Chip siliconchip.com.au D9 1N4004 REG1 7809 +9V OUT REG2 7805 +5V OUT REG3 LM317T +3.3V OUT R1 110 470 F 16V 100 F 16V IN GND IN IN 12V DC INPUT 470 F 25V GND 470 F 25V ADJ R2 180 220 F 16V 470 F 16V R3 0 +5V 10 (ALTRONICS LCD MODULE PIN NUMBERS SHOWN; JAYCAR MODULE PIN NUMBERS IN BRACKETS) 4 15 2(1) Vdd ABL CONTRAST VR1 1k RS 16x2 LCD MODULE CONTRAST 3 6 EN (D7) (D6) (D5) (D4) (D3) (D2) (D1) (D0) 11 14 12 MR Q1 SRCK Q2 Q3 DS LCK Q0 IC2 Q4 74HC595 Q5 Q6 Q7 13 Q7' OE (8) GND 1(2) R/W 5 KBL 16 (7) (9) (10) (12) (11) D0 D1 D2 D3 D4 D5 D6 D7 7 8 9 10 11 12 13 14 (14) 16 Vdd 1k (13) 100nF 10 S9 ON/OFF A K 15 K A 1 2 3 4 S1-S8 5 6 K 7 A D1-D8 9 Vss 8 100 +9Vf 470 F 10k 8 3 2 10 F VR2a 10k LOG IC4a 1 100k 100 100 F LINE OUTPUTS 22k 22k 10k 1000 F 100nF 10k 22k 220nF 100 F PLAY VOLUME 5 6 IC4b 7 100 4 VR2b 10k LOG 7809, 7805 LM317T GND 10 F 100k 22k 10k OUT 220nF D2–D9: 1N4148 A ADJ IN GND OUT siliconchip.com.au OUT K 1N4004 IN A K August 2009  35 Main Features & Specifications • • • • • • • • Uses an MMC/SD/SDHC card to store audio files • • Unit can learn remote control codes • THD+N: 0.7% at 1kHz Stores mono recordings as Microsoft WAV files at 16kHz sampling rate Plays back Microsoft WAV files at up to 44.1kHz sampling rate Uses FAT/FAT32 file system (transfer files to any PC operating system) Has mono microphone and line inputs for recording Stereo socket for line output or headphone use 2-line LCD to display file names, show volume and other settings Can be controlled using on-board switches or any RC5 universal remote control Signal-to-noise ratio: -70dB unweighted (22Hz to 22kHz) with respect 1.6V RMS The microphone itself can be an on-board electret microphone insert or you can use a PC microphone (eg, Jaycar AM-4087) plugged into the 3.5mm stereo input jack – see photo. A 2.2kΩ resistor provides the biasing current for the electret microphone and its DC supply is decoupled from the +9Vf supply using a 100Ω resistor and 100µF capacitor. IC3b is the line input preamplifier. It has a gain of 5.5 (+14.9dB), as set by the 100kΩ and 22kΩ feedback resistors connected to pin 6. The outputs of both preamplifier stages are fed to the ADC inputs (AN0 & AN1) of IC1 via 150nF capacitors. Each ADC input is biased to half the +3.3V rail via voltage dividers, each consisting of two 39kΩ resistors. Power supply However, it’s also used to read from and write to the MMC/SD/SDHC card. This means that we are using the MMC/SD/SDHC card in SPI mode (MMC/SD/SDHC cards can be used in either native mode or in SPI mode). The advantage of SPI mode is that any off-the-shelf microcontroller that has an SPI peripheral can be used, making the hardware layer easy to implement. The interface with SPI may be simple but the penalty is slower transfer speeds. However, SPI speeds are adequate for real-time playing (and recording) of audio. SPI also requires less interface pins and they are at a premium, as you can see. Analog stages The outputs of the two internal DACs are fed via dual-gang potentiometer VR2 to an LM833N low-noise dual op amp (IC4a & IC4b). Both op amp stages are wired as AC-coupled non-inverting amplifiers with a gain of 5.5. The 220nF capacitor to ground from each feedback divider network rolls off the DC gain and sets the lowfrequency response. The outputs at pins 1 & 7 are each fed to the line output socket via a 100Ω resistor and a 100µF capacitor and can either drive stereo headphones or the line inputs of a stereo amplifier. Note that the LM833 is not really intended for driving low impedance loads but it is a low-cost solution for a headphone output. There are two analog input channels, the microphone input and the line input, and they are provided by another LM833N low-noise dual op amp (IC3). IC3a is the microphone preamplifier. It is a non-inverting stage with a gain of 221 (+46dB), as set by the 220kΩ and 1kΩ feedback resistors connected to pin 2. The 4.7µF capacitor sets the low-frequency rolloff. On-Board Control Button Functions If you don’t wish to use a remote control with this project, you can use the on-board buttons to control it. Their functions are as follows: Functions while not playing or recording: S1: Random Shuffle S2: Up S3: Record Mic S4: Delete A File S5: Record Line In S6: Down S7: N/A S8: Play 36  Silicon Chip Functions while playing or recording: S1: Volume Up S2: N/A S3: Choose Display Up S4: Stop S5: Choose Display Down S6: N/A S7: Volume Down S8: Pause The circuit can be powered from either a 12V battery or a 12V DC plugpack supply. In operation, the 12V DC supply is fed in via on-off switch S9 and reverse polarity protection diode D9. Note that a 470µF 25V capacitor is connected adjacent to the DC input socket and is not protected from reverse polarity by D9 (this reduced the hum the most). There are three 3-terminal regulators to provide the required supply rails. First, a 7809 9V regulator (REG1) provides the 9V rail for the analog stages. It has 470µF and 1000µF capacitors across its output at different positions on the PC board. Further decoupling is provided by a 100Ω resistor and 470µF capacitor to provide the +9Vf rail which provides the biasing for the op amp stages. The main +9V rail is also fed to REG2, a 7805 regulator, to derive the +5V rail. This is used to power the LCD module, shift register IC2 and the infrared receiver module (IRD1). This +5V rail also feeds REG3, an LM317T adjustable voltage regulator. This produces the +3.3V rail that’s used by the microcontroller and MMC/ SD/SDHC card. The accuracy of the +3.3V rail is important because some MMC/SD/SDHC cards operate over quite a narrow voltage range. The firmware checks that the inserted card operates at 3.3V and so it is crucial that the supply rail be quite close to +3.3V. The output voltage of REG3 is set by the divider network between its output terminal and its ADJ terminal siliconchip.com.au MMC, SD & SDHC Memory Cards Both MMC (MultiMedia Card) and SD (Secure Digital) cards are a type of nonvolatile storage that uses FLASH memory technology. Similarly, SDHC (HC = high capacity) cards are a type of SD card with capacities between 4GB and 32GB. All three types of cards can be used with this project. While they all look alike, MMC cards have only seven contacts, whereas SD cards have nine. Note that miniSD and microSD cards can also be used as these are essentially SD cards with a smaller form factor. You will, however, need an external adaptor to convert them to standard size to connect to the Digital Speech Recorder. MMC/SD/SDHC cards are commonly used in portable devices like mobile phones, computers, cameras and audio players, among others. They conveniently store a lot of data in a small form factor, consume little power and are light. Cards with increasingly larger storage capacity have been steadily appearing since their introduction in the late 1990s. Helping to put you in Control Control Equipment Digital Stepper Motor Drives We could not believe the speed and quietness of these new drives. Based on a DSP with advanced control algorithm. Software is provided to tune the performance resulting in faster, cooler and quieter stepper motors From $99+GST Digital Servo Motor Drive This is a1880VDC, 0-20A, 20-400W drive. It is based on DSP control technology and high smooth servo control algorithm. It has a PC based and handheld configuration tools, including Pro Tuner for easy tuning. $229+GST LEVEL (dB) Serial Graphic LCD The Serial Graphic LCD backpack is soldered to the 160x128 pixel (100x130mm) Graphic LCD and provides the user a simple serial interface to a full range of controls. $99.95+GST Serial 7 Segment Display FREQUENCY (Hz) Fig.2: this graph shows the frequency response for recordings made on the Digital Speech Recorder. Note that the response is limited to half the sampling frequency which is fixed at 16kHz for recording. The frequency response can be much wider for files recorded on a PC and transferred to the memory card. to ground. The output is set at: VOUT = 1.25V x (1 + (R2/R1)) With R2 = 180Ω and R1 = 110Ω, we get a supply of 3.29V (close enough to 3.3V). However, the 1.25V reference in the regulator can vary between 1.2V and 1.3V. For this reason, provision is made on the PC board for an additional resistor (R3) to allow you to adjust the 3.3V supply rail if necessary. We will touch on this point later, in the setting-up procedure. Construction All parts are mounted on a singlesiliconchip.com.au sided PC board coded 01108091 and measuring 164 x 136mm. Fig.3 shows the parts layout on the board. The first thing to do is to carefully inspect the board for hairline cracks and for shorts between adjacent tracks. It’s rare that you will find a fault but it’s easier to spot any problems at this stage than after the parts have been installed. Begin the assembly by soldering in the 18 wire links. You can straighten the link wire by clamping one end in a vice and then pulling on the other end with a pair of pliers to stretch it slightly. Don’t forget link LK1 under the LCD module. The display can be controlled in one of two ways: (1) serial TTL communication or (2) SPI serial communication. The display will give you full control of all digits, decimal points, the colon and the apostrophe. 50x15mm $17.50+GST MyPCProbe Is a simple to use temperature or temperature and humidity sensor which connects to a PC via a USB port. It comes with an intuitive and easy-to-use Windows software which plots and records data, shows gauges, bargraphs and digital readouts. From $149+GST Large 7 Segment Display. No really this display is 153mm tall and can be seen from 30 metres plus away. A controller is coming soon $19.95+GST Contact Ocean Controls Ph: 03 9782 5882 www.oceancontrols.com.au August 2009  37 12V DC IN D9 470 F 25V 4004 (JAYCAR LCD MODULE) 470 F 25V B.v eR 19080110 REDR O CER H CEEPS 9 0 0 2/ 5 0 G M + REG1 7809 + + 470 F 16V 100 ALTRONICS LCD MODULE REG2 7805 LK11 + S9 470 F 16V 1k LED2 100 100 100 LED1 100 F 10 F 100 F VR2 2x10k LOG S LED3 PLAY VOLUME LINE OUT 100 2.2k 4.7 F 100k 220k 100k IC3 LM833 220nF 100k 100k LK17 100nF 100nF R T LK16 LK18 22k 22k R 1k 100nF 22k 100 100 + (PS-0024) 100 F + MMC/SD/SDHC CARD SOCKET (UNDER) 10 F + LK5 39k IRD1 39k 39k 39k 39k 10 100nF 150nF 10k 10k 10k 10k + LK4 1k IC1 dsPIC33FJ64GP802-I/SP 10 F TANT + 100k LK12 + 27k 27k VOL DOWN 22k N/A 100nF 100k DISPLAY DOWN X1 100nF 150nF S7 S6 LK13 LK14 LK15 N/A IC4 LM833 LK10 LK9 LK7 LK8 LK6 S5 100 F 100nF 220nF LK1 2.2k 18pF 10 F 18pF + PAUSE DOWN REC LINE IN + 22k LK3 STOP 10 1000 F 100k 0 180 + 16V VOL UP PLAY S8 S4 100 F 110 N/A + + 470 F S1 DISPLAY UP DELETE FILE IC2 74HC595 100nF 220 F SHUFFLE UP + LM317T + 4148 4148 D1 D5 10 4148 D2 D6 4148 REC MIC 4148 4148 D3 D7 4148 4148 D4 D8 S2 S3 VR1 REG3 LK19 14 13 12 11 10 9 8 7 6 5 4 3 2 1 16 15 LK2 + MIC R S LINE IN T S T MIC IN Fig.3 (above): install the parts on the PC board as shown on this parts layout diagram. Take care to ensure that all polarised parts are correctly oriented and leave the ICs and the LCD module off the board until after the initial power supply checks have been completed. Fig.4 (left): the memory card socket (CON1) is a surface-mount device (SMD) and is installed on the underside of the PC board as shown here. Lightly solder tack one pin first, then check the socket’s alignment before soldering the remaining pins. The resistors are next on the list and again one of these is under the LCD module. Table 1 shows the resistor colour codes but you should also check each resistor using a DMM before soldering it to the board. Resistor R3 can be either a 0Ω resistor or you can simply install a wire link (note: this 0Ω resistor may have to be changed later – see section on trimming the 3.3V rail). 38  Silicon Chip Follow these parts with the diodes and the infrared receiver (IRD1). Note that D9 is a 1N4004 type, while the remaining eight diodes (D1-D8) are all 1N4148 signal types. These diodes must all be installed with the correct orientation (the striped end is the cathode), while IRD1 must go in with its domed lens facing outwards. The three LEDs (LED1-3) can be installed at this stage as well. Make sure that these are oriented correctly and match the colours shown on Fig.3. Installing the regulators The three TO-220 regulators (REG1REG3) can now go in. As shown, these are all mounted horizontally, with their leads bent down at right-angles about 6mm from their bodies. In addition, the 7805 regulator must be fitted with a mini heatsink before it is bolted siliconchip.com.au Table 2: Capacitor Codes Value 220nF 150nF 100nF 18pF µF Value IEC Code 0.22µF 220n 0.15µF 150n 0.1µF 100n NA   18p EIA Code    224    154    104     18 This prototype PC board differs slightly from the final version shown in Fig.3 on the facing page. Table 1: Resistor Colour Codes o o o o o o o o o o o o o siliconchip.com.au No.   1   7   5   2   5   4   2   3   1   1   7   1 Value 220kΩ 100kΩ 39kΩ 27kΩ 22kΩ 10kΩ 2.2kΩ 1kΩ 180Ω 110Ω 100Ω 0Ω 4-Band Code (1%) red red yellow brown brown black yellow brown orange white orange brown red violet orange brown red red orange brown brown black orange brown red red red brown brown black red brown brown grey brown brown brown brown brown brown brown black brown brown black 5-Band Code (1%) red red black orange brown brown black black orange brown orange white black red brown red violet black red brown red red black red brown brown black black red brown red red black brown brown brown black black brown brown brown grey black black brown brown brown black black brown brown black black black brown black August 2009  39 Transferring Files & Recording To The Memory Card To transfer audio files from a PC to the memory card, you will need a low-cost SD/ SDHC/MMC-card reader. The one shown in the accompanying photo is available from Jaycar for less than $10 (Cat No: XC-4756). Note that before copying the files (eg, music tracks) to the MMC/SD/ SDHC card, they must first be converted to WAV format. This can be done using a freeware sound editor program called “Audacity” – see panel on page 33. As indicated earlier, you can also directly record files to a memory card in the Digital Audio Recorder. Basically, you have two choices when making recordings: either use the microphone input or feed signals in down. Each regulator is secured using an M3 x 5mm machine screw and nut. The next step is to install the four IC sockets. If you don’t have a 28-pin 0.3-inch socket (or have a 0.6-inch socket instead), you can cut it down the middle and install the two strips for IC1. Orientate each socket so that its notch matches that shown on the overlay. This will make it easier when it comes to installing the ICs later on. You will also need to cut down a 40-pin IC socket to make the connector for the LCD module. If you are using via the recorder’s line input. When using the microphone input, you can use either an onboard electret microphone (see photo) or you can plug an electret microphone into the MIC In socket. Suitable external electret microphones are available from Jaycar and Altronics. Be sure to disconnect the on-board microphone if you are using an external microphone. Note that the microphone and line inputs differ in the gain of their respective preamplifier stages, so be sure also to choose the correct input. the Altronics module, you will need a single row of 16 pins. Alternatively, if you are using the Jaycar module, you will need two rows of seven pins and they must be installed with what were originally their outside edges touching in the middle, otherwise they won’t fit in place. Now move on to the capacitors. There are four different types: monolithic, ceramic, MKT and electrolytic. The first three types can go in either way around but the electrolytic capacitors are polarised and each must Defining The Remote Control Codes If you wish to use a remote control with this unit, you will need an RC5compatible remote. RC5 is an infrared communications protocol that was initially developed by Philips and is used by many Philips appliances. This means that if you have a universal remote, there’s a good chance it will work if you set it to control a Philips appliance. For example, we tested the project with the Jaycar AR-1726 remote and can confirm that it works. Setting up the remote is straightforward. You start by pressing the S2 & S6 (UP & DOWN) buttons together 40  Silicon Chip while booting the recorder, to enter the remote control programming menu. You are then prompted to press the key you want to define for that function. For example, you may be prompted to “Press Play” and you then simply press the relevant button on the remote which is to be assigned that function. A recommended set-up using the AR-1726 Remote from Jaycar is shown in Table 3. It should be set to the VCR 917 code which corresponds to the default programmed into the recorder’s firmware. This larger-than-life size view shows how the card reader is mounted on the copper side of the PC board. be oriented as shown on Fig.3. The negative terminal is marked on the body of each capacitor. The switches can go in next. The power switch (S9) is a DPDT slide type, while the rest (S1-S8) are momentary pushbutton tactile types. Note that these tactile switches are not symmetrical in the horizontal and vertical directions, being slightly longer in the vertical direction. It’s just a matter of installing them with their terminals positioned as shown (they won’t fit the wrong way). The larger items can now be installed. These include trimpot VR1, dual-gang potentiometer VR2, the DC connector and the three 3.5mm stereo jack sockets. If you intend using an electret microphone, then you will also have to install a 2-pin socket strip to accept its connecting leads. Note that the electret microphone should not be connected while you are using an external microphone. Installing the card socket The memory card socket is mounted in the underside of the PC board – see Fig.4. This is an SMD device so you must carefully position it over its pads and solder one of the pins first to anchor it in position. Once that is done, you can solder the rest of the pins. Note that there are two mounting terminals on either side of the device that must also be soldered to matching pads near the front edge of the board (see Fig.4 and photo). The initial assembly can now be completed by fitting four M3 x 12mm Nylon spacers to form the mounts for siliconchip.com.au Table 3: Recommended Key Assignments For Digitech AR-1726 Remote Control Button Recommended Key Definitions for the Digitech AR-1726 Remote Function(s) 0 Unused Press ‘0’ 1 In Triggered mode, used to play file rec001.wav Press ‘1’ 2 In Triggered mode, used to play file rec002.wav Press ‘2’ 3 In Triggered mode, used to play file rec003.wav Press ‘3’ 4 In Triggered mode, used to play file rec004.wav Press ‘4’ 5 In Triggered mode, used to play file rec005.wav Press ‘5’ 6 In Triggered mode, used to play file rec006.wav Press ‘6’ 7 In Triggered mode, used to play file rec007.wav Press ‘7’ 8 In Triggered mode, used to play file rec008.wav Press ‘8’ 9 In Triggered mode, used to play file rec009.wav Press ‘9’ VOL UP In Normal mode, used to select a file to play. While playing, used to increase the volume Press ‘Vol Up’ VOL DOWN In Normal mode, used to select a file to play. While playing, used to decrease the volume Press ‘Vol Down’ CH UP While playing, used to select what is displayed in the second line on the LCD module Press ‘Ch Up’ CH DOWN While playing, used to select what is displayed in the second line on the LCD module Press ‘Ch Down’ MENU Used to delete the selected file; confirmation is requested Press ‘Menu’ STOP Used to stop a playing file or a recording Press ‘Stop’ PLAY Used to play the selected file Press ‘Play’ PAUSE FAST FWD Used to pause a playing file or a recording Used to start random shuffle Press ‘Pause’ Press ‘FF’ REWIND Unused RECORD Used to initiate a recording from the microphone input Press ‘Rec’ OK Unused Press ‘Ok’ EXIT Unused Press ‘Exit’ LINE Used to initiate a recording from the line input the PC board. DO NOT fit the ICs or the LCD panel at this stage. These parts are installed only after the supply rails have been checked and that step comes next. Power supply checks You will need a 12V DC 300mA (or higher) regulated plugpack with a 2.5mm connector to power this project. Suitable plugpacks include the Jaycar MP-3147 and the Altronics M-9243. However, you will need to cut off the 2.1mm connector on the Altronics unit and replace it with a 2.5mm connector. Be sure to get the polarity correct – the centre pin is positive. Before applying power, make sure that the LCD is unplugged and that no ICs have been fitted. That done, apply power and move S9 to its ON position (ie, to the right). Now, using a DMM, measure the voltage between siliconchip.com.au Press ‘Rewind’ the OUT and GND terminals of REG1 – you should get a reading of 9V. If not, switch off immediately and check for supply errors. If no voltage is present, then D9 may be reversed or the supply polarity could be incorrect. Assuming all is OK, check the voltage on the OUT terminal of REG2. This time, you should get a reading of 5V. Finally, check the voltage on the OUT terminal (ie, the centre terminal) of REG3. It should be close to 3.3V. If any of the above voltages is incorrect, disconnect power immediately and check your work. Note: the OUT terminal of REG3 is the centre lead of the device. By contrast, the OUT terminal of both REG1 & REG2 is one of the outside leads – see Fig.1 for the pin-outs. Trimming the 3.3V rail If the 3.3V rail is more than 3.4V or Press ‘->’ less than 3.2V, you will need to change one or both of the values for R2 and R3. For example, if the voltage from REG3 is 3.17V, you will need to install a 10Ω resistor for R3 and this should bring it pretty close to 3.3V. Alternatively, if the output voltage is 3.41V, you should change the value of R2 to 160Ω and R3 to 10Ω, giving a total value for R2 + R3 = 170Ω (or you could use 150Ω for R2 and 22Ω for R3). Again, this should bring the voltage from REG3 pretty close to 3.3V. If all three supply voltages are now close to their nominal values, you can disconnect power and insert the four ICs in their sockets. These ICs should all be oriented correctly of course. Installing the LCD module The LCD module can now be installed. The Altronics module is secured to the board on two M3 x 9mm August 2009  41 Screen grab showing the playing view. The time since the beginning of the track and the volume level are shown. Note that the time will blink on and off if track is paused. Screen grab showing file selection. You can scroll through the file system by using the Up and Down buttons and press Play when you are satisfied with your selection. The currently selected file is shown with '>'. The previous directory is shown as '[..]'. You can press Play or Record to enter a directory. Note that directory names are enclosed in square brackets to differentiate them from normal files. The playing view. The time since the beginning of the track, the sampling rate and whether the track is mono or stereo are shown. This view shows that the sampling rate is 44.1kHz and it is a stereo track that’s being played. The recording view. The time since the beginning of the track, the sampling rate and whether the track is mono or stereo are shown. This view shows that the sampling rate is 16kHz and that it is a mono track that’s being recorded. When playing a random selection through shuffle, this is the play screen shown. Notice the 'RND' indicator that's only shown in this mode. A screen readout showing the size of the inserted memory card and the remaining free space on it. This screen is displayed once on startup. Fig.5: this diagram show some typical displays on the LCD, together with accompanying explanations. The unit shows file names, time elapsed while playing, the recording source, volume, sampling rate, card size, free space and other information. tapped Nylon pillars as shown in Fig.3, while the alternative Jaycar module is secured using four M3 x 9mm tapped Nylon pillars, ie, one at each corner (all the necessary mounting holes are on the PC board). Your Digital Speech Recorder & 42  Silicon Chip Audio Player is now completed and ready for use. You should transfer the audio WAV files you wish to play to an MMC/ SD/SDHC card using your PC or Mac, making sure the card is formatted with a FAT/FAT32 file system. Once the memory card has been inserted in its socket on the underside of the PC board, you can apply power. The firmware should display the version on the LCD panel and then compute the free size on the memory card. Your player is then fully operational. Configuring the unit The Digital Speech Recorder can be used in either of two modes: normal or triggered. By default, the unit works in normal mode. However, if you wish to configure it for triggered operation, you simply create a file “trigger.txt” and place it in the root folder of the memory card you are using. You can do this using a card reader and a PC. The file need not contain anything – it just needs to be there (as an empty file). The microcontroller will look for this file on boot up and switch the mode of operation to triggered if it is present. On the other hand, if this file is absent, the recorder boots for normal operation. The differences between these two modes of operation are explained below. Normal mode In Normal operation, you begin by using the UP and DOWN buttons (S2 & S6) or the VOL UP and VOL DOWN buttons on the remote control to scroll through the file system on the card. When you’ve selected the correct file, you simply press PLAY (S8) to play it. A screen grab showing a typical view of the filesystem is shown in Fig.5 (second from top). Of course, only two files are ever shown at any one time. A directory is indicated by its name being enclosed in square brackets. Press PLAY to enter a directory. The previous directory is shown as “[..]” – see Fig.5. The delay in playing a new file is very small, of the order of a fraction of a second. This makes this project perfect for playing sound effects on demand. Pressing SHUFFLE (S1) or FAST FF on the remote enters random shuffle mode. In this mode, there is an “RND” indicator on the display and a random selection of tracks (eg, songs) is continuously played from the root directory. You exit this random shuffle mode by pressing STOP (S4). Pressing REC MIC (S3) or REC LINE-IN (S5) starts a recording from the microphone or line input respecsiliconchip.com.au Configuring The Software To Suit The LCD Module If you look closely at the PC board for this project, you will notice that the Jaycar and Altronics LCD modules are wired with their data lines “transposed”. Basically, the D0 line on the Altronics module is connected to the D7 line of the Jaycar module, while the D1 line on the Altronics module is connected to the D6 line of the Jaycar module and so on. This was done to simplify the PC board layout. It means, however, that the firmware must drive these two LCD modules differently. As a result, the microcontroller must either be programmed with 0110809A.hex if you are using the Altronics LCD module or with 0110809J. hex if you are using the Jaycar LCD module. You can also toggle either version to drive the alternative module. This is done by holding down buttons S4 & S8 together while applying power. Note that this needs only to be done once, as the new setting is stored in non-volatile memory. If nothing appears on the LCD at initial switch-on, try adjusting the contrast (VR1). If that doesn’t work, you may have the wrong software for your particular LCD module, so switch off and reapply power while holding down S4 & S8. If you buy a kit, then the default will be correct for that kit supplier’s LCD module. tively. Alternatively, you can press the Record or Line buttons on the remote. When recording a file, the filename will be of the form rec???.wav with ??? a string of three decimal digits. The filename recorded will be shown when the recording is ended using either the STOP button (S4) on the board or the STOP button on the remote. In practice, it’s more complicated “in the telling” than “in the doing”. A few minutes spent pressing buttons will quickly reveal how it works. Triggered Mode In Triggered mode, you simply press one of the eight buttons to play the file “rec00?.wav” where “?” is a digit from 1-8. For example, pressing S3 will play the file “rec003.wav”. This close-up view shows how an on-board electret microphone can be installed (it plugs into a 2-pin header near the external microphone socket but watch the polarity). Do NOT install this if you intend using an external mic. You can also press the corresponding digits on the remote control to play each of these eight files. Basically, the Triggered mode is useful for quickly playing back one of eight tracks (or messages) once they have been recorded. After recording the messages (using Normal mode), it’s just a matter of copying a file called “trigger.txt” to the root folder of the card as detailed above and restarting SC the Digtial Speech Recorder. 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See the order form in this issue. 294 - 4 TURBO B OOST & nitr ous fuel co ntrollers 6 NZ $22.00 (inc GST) How eng in manageme e nt works Order by phoning (02) 9939 3295 & quoting your credit card number; or fax the details to (02) 9939 2648; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. siliconchip.com.au August 2009  43