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How to add a wireless infrared port to the DSP Musicolour – or in fact virtually any microcontroller project. Musicolour IrDA Accessory By Mauro Grassi Most PCs and laptops now offer an IrDA interface to enable communication without any physical connection. Now you can have the same facility for the DSP Musicolour – or for virtually any other microcontroller project. I n the June, July and August 2008 issues of SILICON CHIP we described the DSP Musicolour, an advanced light show based on the dsPIC30F4011 microcontroller from Microchip. We mentioned that the firmware supports a high speed UART (Universal Asynchronous Receiver Transmitter). The PC board below (which in fact can replace the September infrared remote control PC board) adds an IrDA (Infrared Data Association) compatible serial port for the DSP Musicolour. This gives you all the features the original remote control offered but adds a huge amount of additional features via the serial port of your PC. Although the firmware in the DSP Musicolour supports a high speed UART running at up to 1.84Mbps, this interface will run at the much slower baud rate of 9.6Kbps, which is the default baud rate of the DSP Musicolour. There is little need for it to be higher as 9.6Kbps should be fast enough for most applications (if you wish to use a higher baud rate, you could connect a wired The component (upper) side of the serial port). IrDA is ideal for PC board is the less interesting side – IC1 and the adding a serial port to infrared receiver/transmitter are a mains-rated circuit mounted on the other (copper) side. siliconchip.com.au as the UART is completely isolated. Since it is infrared, it is also very convenient. Operating distance is not great – the specification says around 1m (without any obstacles) – but we found it works over greater distances than that. Although this circuit was designed specifically for the DSP Musicolour, it could be adapted so as to add an IrDAcompatible serial port to any microcontroller project. We give you a recommended circuit to do this. Because it was designed specifically for the DSP Musicolour, it also includes an infrared remote control receiver, thus effectively superseding the small infrared remote control PC board published in the September 2008 issue of SILICON CHIP. However, that project is still perfectly valid if you just want to control the DSP Musicolour using a remote control. Protocol controller Essentially, the circuit (shown in Fig.1 overleaf) is little more than a couple of infrared devices and a dedicated IrDA standard protocol controller IC from Microchip, the MCP2140A (IC1). This IC does most of the hard work of communicating and setting up the connection with your PC. We suspect that internally, this IC is nothing more than a PIC microcontroller with a custom program. November 2008  71 47 IRD1 TFDU-4300 6 Vcc A 14 IREDA IrDA Tx/Rx VL IREDK TXD RXD GND SD 10k 1 7 12 6 2 3 2 4 18 5 100nF CTS PHACT Tx TxIR RxPD 11 10k IRD2 (ZD-1952) 13 IC1 MCP2140A RST RI Rx OSC1 DTR RTS CD DSR NC 1 RxPD REF 22 F 16V 8 Vdd OSC2 2x 470 17 10 TO MAIN BOARD A  LED1  LED2 K K CON1 5 8 3 7 7 6 4 1 9 2 8 10 9 16 3 X1 3.6864MHz 15 4 Vss 5 22pF 22pF 3  1 470 IRD2 2 IRD1 LEDS SC  2008 MUSICOLOUR IRDA BOARD K A 1 2 3 4 5 1 6 7 8 3 2 Fig.1: the circuit is very simple, consisting of little more than a couple of infrared devices (IRD1 & 2) plus a dedicated IrDA standard protocol controller (IC1). CON1 connects to CON3 on the back edge of the DSP Musicolour PC board. In fact, Microchip provide the IrDA protocol stack source code as a free download on their website. laptop motherboards and PDAs. In fact, we used a similar transceiver in a previous design to add an IrDA port to your desktop PC (SILICON CHIP December 2001). Don’t use the MCP2140! The operation of IRD1 is simple enough. Pin 1 (IREDA) is Note that the MCP2140 was the original IC in this sethe anode of the internal infrared LED while pin 2 (IREDK) ries but the MCP2140A is operationally different. The is the cathode. In normal operation, you connect IREDA to MCP2140A will not work as a replacement for the MCP2140 the supply rail (in this case around +5V) and leave IREDK and vice versa. That’s because the MCP2140A works with disconnected. IREDK can be used externally to turn on a 3.6864MHz crystal, whereas the MCP2140 works with the LED but in our case, the LED is switched on and off by a 7.3728MHz crystal. The two ICs require different input internal logic. signals into pin 18, too. Note that a current limiting resistor is not needed to Speaking of the 3.6864MHz crystal, it connects to the two IREDA as the internal circuit of IRD1 limits the current internal oscillator pins of IC1 (OSC1 and OSC2) to provide through the LED. the system clock. A pair of 22pF ceramic capacitors provide Pins 3 and 4 of IRD1 are the transmit and receive lines the correct loading for the crystal. respectively, encoded as RZI (Return to Zero Inverted) signals. The MCP2140A translates the NRZ (Non Return to Infrared transceiver IRD1: the Vishay Zero) encoding at its Tx and Rx pins to RZI signals at its TFDU4300 TxIR and RxPD pins. To receive and transmit data over an IrDA link, we use The IrDA is only half duplex because the standard does not a Vishay TFDU4300 (IRD1). This is an IrDA compatible specify any optical isolation between the transmitter transceiver, consisting of a transmitting LED and a and receiver. When IRD1 is transmitting through receiving phototransistor. There is also a small its internal infrared LED, the receiver will also amount of logic on the transceiver turn on, because the phototransistor is biased as well as an amplifier. Such into conduction by the infrared light from transceivers are comthe transmitting LED. The MCP2140A monly found on drives the transceiver in half-duplex mode while presenting a full duplex interface to the host device (in this case, the dsPIC30F4011). Pin 5 is the shutdown pin (SD), which IC1, IRD1, IRD2 is active high. When high, IRD1 goes into and the two LEDs are power conservation mode, drawing a very all mounted on the copper small current (typically down to 0.1μA at side of the PC board. IC1’s and IRD1’s room temperature). This is useful for battery powered aplead spacings are very fine– a steady hand and a fine-tipped soldering iron are essential. plications but in our case, where we are 72  Silicon Chip siliconchip.com.au LK4 1 2 LK3 X1 22pF LK1 CON1 LK2 9 10 22 F 470 10k 22pF + 47 10k 100nF 470 CS 10111081 470 LK5 (TOP OF BOARD) IRD1 1 IC1 IRD2 MCP2140A 1 1 LED2 SC 10111081 LED1 Figs.2a and 2b (left) show both sides of the PC board, with matching photos at right. Note that the 22µF capacitor needs to be installed flat, otherwise there would not be room for the PC board inside the DSP Musicolour case. These diagrams/pics are reproduced 1:1. (UNDERSIDE OF BOARD) supplying power from the Musicolour supply, we ignore this connection and tie it permanently to ground. Pin 6 is the supply voltage to IRD1 and pin 7 (VL) selects the voltage level for the logic. This makes IRD1 customisable to different logic families with different threshold voltages. In our case, we connect it to the +5V supply rail. Finally, pin 8 is the ground connection for IRD1. The 22μF electrolytic capacitor is used to bypass the supply rail to IRD1 through the 47Ω resistor. The capacitor and resistor isolate the transceiver from a possibly noisy supply rail, which can interfere with IRD1’s sensitive internal receiving circuit. The two 10kΩ resistors form a voltage divider and are used to split the supply voltage and set the threshold for the receiving logic level for IC1. Any level above the voltage at pin 1 of IC1 (RxPD Ref) is interpreted as a high level. Conversely, any level below that is interpreted as a low level. This pin therefore sits at around 2.5V. A 100nF capacitor is used to bypass this rail. The DSR (Data Set Ready) output of IC1 will go low (thus turning on LED1 (green)) when a valid connection has been established with the host. It is locally emulated by IC1 and can indicate to a microcontroller that IC1 is ready to receive and transmit data. Thus LED1 indicates that the MCP2140A has established a valid connection with your PC. The PHACT (physical activity) output of IC1 (pin 3) is open collector and will sink current (thus turning on LED2 (red)) when there is a period of inactivity from the receiver for around 10 seconds. This pin can be pulled up to the supply rail using a resistor (1kΩ will do) and can then control pin 5 (SD) of IRD1 through an inverter, if desired. In this configuration, it puts the transceiver in low power mode after a 10-second timeout. In our case, we use the output to control LED2 and to indicate to the user that no signal has been detected for at least 10 seconds. This can be useful for troubleshooting. Pin 7 (Tx) and pin 8 (Rx) are the UART transmit and receive lines while RI (Ring Indicator), CD (Carrier Detect), DTR (Data Terminal Ready), RTS (Request to Send) are all part of the serial port handshaking signals. Normally, IC1 will transmit and receive the state of these lines to the PC, emulating a full serial port. In our case, we are really only using the raw 3-wire serial port so we ignore these handshaking lines. We tie the DTR line to ground, ignore the CTS output of IC1 and connect RI to Rx. This is done simply to make the layout of the PC board more compact. In any case, we only care about the Tx and Rx lines and these connect to the corresponding lines on the dsPIC30F4011 through CON1. siliconchip.com.au However, the RTS input of IC1 (pin13) is used locally to indicate that the MCP2140A is ready to receive data. We therefore tie this line permanently to ground. Finally, pin 4 (/RST) is an active low reset pin and is tied directly to pin 1 of CON1 (which connects to CON3 of the DSP Musicolour main board and is the reset line of the dsPIC30F4011 microcontroller). The other infrared module (IRD2) is used for the RC5 remote control decoding and is really a separate circuit on the same PC board. Pins 3 and 2 provide the supply for IRD2 and pin 1 is the decoded remote control data, very similar to the remote control add-on board we described in the September 2008 issue of SILICON CHIP. A 470Ω resistor is used between the output of IRD2 and pin 9 of CON1 because pin 9 connects to the RF6 pin of the dsPIC30F4011 on the DSP Musicolour main board. Because this pin can sometimes function as an output, the resistor is used to limit the current into the data output pin of IRD2. Construction This is a simple PC board that should take a matter of minutes to build. Fig.2 shows the parts layout. The Musicolour IrDA PC board is coded 10111081 and measures 61mm x 20mm. Inspect the board for any hairline cracks or unintended shorts before beginning the assembly. If you are satisfied that the PC board is good, begin by installing the six wire links. Fig.3: oscilloscope screen grab showing the NRZ encoding for a typical RS232 signal at the PHY. November 2008  73 The IrdA board is sandwiched between the DSP Musicolour display board and the red acrylic front panel, with a piece of non-conductive foam holding it in place. Here’s what it looks like from above – in this photo you can mostly see the black foam. The connecting cable curves around the edge of the display PC board. Once that is done, install the six resistors. The resistor colour codes are shown in the colour code table but you can check them with a DMM too. After soldering these, you can solder in the capacitors. Start with the two ceramic capacitors near the crystal, then install the small monolithic. Finally, install the larger electrolytic capacitor, which must be oriented correctly, as shown on the component overlay. Solder in the crystal so that it sits flush with the PC board. The top layer components except the IDC header should now look like that in the PC board top layer photograph. Now turn the board over to the bottom layer (where the tracks are). There are two SMD (surface mount devices) on the bottom layer, namely the MCP2140A (IC1) and the TFDU4300 (IRD1). You will need a magnifying lamp (or glass with good light), a fine-tipped soldering iron and a steady hand. You should start with IC1 because it is of relatively large pitch. Place it on its pads, making sure it is oriented correctly. Once it is in place, solder pin 18 by applying heat and a little solder. Once that is done, solder pins 8 and 9 (diagonally opposite pin 18). The IC should then be properly anchored and not able to move. Proceed to solder the remaining 15 pins. The result should be as shown in the photograph. Now comes the hardest part! You need to solder in the IrDA transceiver, which has a finer pitch. Place it on its pads and hold it in place while applying heat and a very small amount of solder to pin 1. You then solder in pin 8 in the same way, before soldering in the remaining pins. Apply heat and solder each pin quickly before moving on to the next pin. Do not apply too much heat as that can damage the plastic case as well as the integrated circuit itself. Don’t worry if you get solder bridges between adjacent pins, as these can be removed by using solder wick. Carefully inspect your soldering, preferably using an illuminated magnifier or loupe and if you find any bridges, remove them. Refer to the article on soldering SMD components on page 22 of the March 2008 SILICON CHIP for more details. Now solder in the infrared receiver module IRD2. You should aim for around 7mm of lead, which will allow you to bend the module down 90° once it has been soldered, so that it sits flush with the PC board (as we have shown in the close-up photo). The two LEDs are similarly bent down 90° after soldering. Make sure that they are oriented correctly. The last thing to do is to solder in the 10-way IDC rightangled header. Again, check for solder bridges once it is soldered in place. You can then connect the Musicolour IrDA board to the DSP Musicolour’s main board using the 10-way ribbon Fig.4: a screen shot from Windows’ device manager showing the ircomm2k driver installed and recognised correctly. Fig.5: screen shot showing Realterm in action communicating with the DSP Musicolour. Soldering the SMD ICs 74  Silicon Chip siliconchip.com.au From the front, without any labelling on the acrylic sheet you can easily see the three main components (the two IRDs and the controller chip) The opposite end of the ribbon cable connects to the same socket on the rear of the PC board as used in the September 2008 article. cable. CON1 connects to CON3 on the DSP Musicolour main board, in exactly the same way as described in the article in the September 2008 issue (pages 72-75). We explained how to make a 26-way ribbon cable connecting the main board to the display board in the July 2008 issue (page 26 under Ribbon Cable Assembly). The 10-way ribbon cable used to connect the remote control board is made in the same way. Your IrDA Board is now complete and ready for mounting in the DSP Musicolour front panel. It is a free download from www.ircomm2k.de/English/ index.html or via a link on the SILICON CHIP website (www. siliconchip.com.au). Follow the installation instructions. Note that your PC must have an IrDA port installed. This is commonly found on laptop computers and PDAs (but not all laptops will have an infrared port). Most modern desktop motherboards also have supporting circuitry for it but will probably lack the optical transceiver. Refer to December 2001 SILICON CHIP if you want to add an IrDA port to your desktop PC. Disconnect power! The first thing to do is disconnect power from the DSP Musicolour – pull the IEC plug out of its socket to make absolutely sure. Then, and only then, open the case. Do not proceed unless you are absolutely sure you know what you are doing. Don’t be tempted to connect power while the case is open – it is too dangerous. Where it sits The IrDA PC board fits between the red acrylic front panel and the display PC board. A piece of foam holds it in place and also insulates it from the components on the display board. This is not an ideal mounting solution . . . but it is just about the only one! Because this board is an add-on, it was not catered for in the original DSP Musicolour design. But we think it’s a practical addition and we’ve made the only mounting decision possible. Again, we have shown a close-up photo to show how it goes in. You can then close the case again by screwing it shut. Using the IrDA board with the DSP Musicolour This add-on board gives the DSP Musicolour a wireless serial port you can use to communicate with a PC. It also allows the DSP Musicolour to be operated using an RC5 remote control, in the same manner as explained in the September 2008 of SILICON CHIP (pages 72-75). You can define the remote control codes as explained in that article. Software for Windows: the IRCOMM2K driver Before communicating with the IrDA board, you will need to install a software driver implementing the IrCOMM protocol on Windows 2000 and XP. siliconchip.com.au Using the IrDA serial port Once you download the zipped ircomm2k driver, extract the files and run setup.exe. The install program will prompt you for the serial port number to install the virtual IR port. Choose a port number (say COM5) that will not interfere with any other (physical) serial ports implemented on your PC. You should then disable the “Wireless Image Transfer” in Windows. Go to Control Panel > Wireless Link and in the image transfer tab, unclick the box selecting “Use Wireless Parts List – Musicolour IrDA Accessory 1 PC board, coded 10111081, 63mm x 21mm 1 3.6864MHz PC board mounting crystal (X1) 1 10-way PC board mounting IDC male connector 1 10-way ribbon cable, approx. 250mm long fitted with female line sockets Semiconductors 1 MCP2140A 1 TFDU-4300 infrared transmit/receive module 1 Infrared receiver (eg Jaycar ZD-1952) 1 3mm green LED (LED1) 1 3mm red LED (LED2) Capacitors 1 22μF 16V electrolytic 1 100nF ceramic 2 22pF ceramic Resistors (0.25W, 1%) 1 47Ω 3 470Ω 2 10kΩ November 2008  75 Link to transfer images from a digital camera”. This needs to be disabled because the Windows service interferes with the ircomm2k driver. Once that is done, you should reboot Windows. If the driver is installed correctly, you should be able to see it under Control Panel > System > Device Manager > Ports COM and LPT > Virtual IR COM Port (COM5), as shown in Fig.4. Installing Realterm The final thing to do is to use a terminal program to communicate with the Musicolour IrDA board. You can use Windows’ hyperterminal if you wish, available under Start > Accessories > Communications > Hyperterminal. Another good program to use is the freely available realterm. Download it from http://realterm.sourceforge.net/ Once that is installed, you can establish a link with the Musicolour IrDA board using COM5 (or whatever number for the virtual IR port you chose in the installation step above). You should set the encoding to 8 bits, 1 stop bit, no parity, 9.6Kbps. As soon as you open Realterm and start typing characters, the green LED (LED1) on the IrDA board will light, indicating that a valid connection has been established. Remember that you need to position your PC or laptop so that its infrared transceiver is in the line of sight of IRD1 and within 1m or so. The characters you type will then be sent via the infrared link to the Musicolour IrDA board and onto the UART on the main board of the Musicolour (ie, on the dsPIC30F4011 microcontroller). A typical screen shot is shown in Fig.5. In the DSP Musicolour menu system, you can go to the CONSOLE > COM submenu. There the DSP Musicolour will display the received characters from the serial port and echo back the same character. You should do this to test that the IrDA board is working correctly. As you type your characters in Realterm, you should see them appear on the dot matrix display of the DSP Musicolour. How to upgrade the firmware of the DSP Musicolour If there are some aspects of the DSP Musicolour’s firmware which 76  Silicon Chip you’d like to change – and you have the knowlege to do so – it can can be upgraded using this infrared port. Using Realterm, you can send a hex file to the DSP Musicolour to force it to reconfigure its flash memory using its RTSP server. To do this, go to the ADVANCED > Write Mode menu and set it to 6 (thus allowing writing of the flash memory). Then go to the ADVANCED > Software Upgrade submenu. Once you enter that mode, the dot matrix display will go blank. The DSP Musicolour will send a string to your Realterm window through the infrared link. You can then use realterm to send a hex file to the DSP Musicolour which will reprogram itself and reset. You should set the line delay to 40ms or higher. You then select the hex file you want to send and click send. Realterm will send each line and wait for the set line delay before sending another line. If manually sending hex file lines, you must send the :00000001FF (end of file) line to indicate to the DSP Musicolour that programming is finished. Once the EOF (end of file) line is received by the RTSP server, the DSP Musicolour will reboot after 10 seconds and the new firmware version will be operational. SC How to modify the PC board to add an infrared serial port to a microcontroller project As we mentioned before, this PC board was designed to interface with the DSP Musicolour main board. But it can easily be modified to add a serial port to your next microcontroller project. The modified circuit diagram below shows a typical application. The levels at CON1 are only TTL levels, adequate for interfacing directly to most microcontrollers implementing a UART. Note that if you wish to interface the modified board directly to a PC and need true RS232 voltage levels, you will need to add a MAX232 or similar IC to translate the TTL levels at CON1 to true IRD1 TFDU-4300 22 F 16V 6 Vcc 47 IREDA VL IREDK TXD RXD GND SD 1 4 RST 10k 7 6 2 3 2 4 18 5 100nF 3 SC 10k 13 5 6 7 CON1 DB9F RS232 (TTL LEVEL) PHACT 3 IC1 MCP2140A DSR CTS Tx CD RI Rx DTR TxIR RxPD OSC1 RTS OSC2 Vss 5 4 IRD1 2008 NC Vdd 1 RxPD REF 8 2 +5V DC INPUT 14 IrDA Tx/Rx 1 RS232 levels (this is not shown in the circuit diagram). The host (ie, the microcontroller) should only send data to the MCP2140A when CTS (Clear To Send) is low. On the other hand, the host should drive DTR (Data Terminal Ready) low when it is ready to receive data from the MCP2140A. The host can then send and receive data from the MCP2140A through the Tx and Rx pins (encoded as NRZ) ultimately to the connected IrDA-enabled PC or PDA (confusingly this is also a host, ie, the IrDA host!). 10 12 7 17 9 8 11 16 6 3 9 X1 3.6864MHz 4 5 8 1 2 7 15 22pF 22pF 8 MODIFIED IRDA CIRCUIT Use this modified circuit to add a wireless serial port to virtually any microcontroller project. Unlike the circuit used specifically to interface to the DSP Musicolour main board, this circuit emulates the full serial port rather than just the Rx and Tx signals. This can be used for handshaking between the microcontroller and IC1. siliconchip.com.au