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1. Meas resin Freetyier apply Charger 73 DSO msn Ge pit prue Setup 2X eeeh a aww saan a ed 7 7 y Aj WT 7 7 D Ei PAN TET jee Figure 9 The number of functions available in FreeStyler makes it quasi professional since there are no holes in the printed circuit The cable shielding is soldered to the connector strip The next step is to solder the circuit to the XLR connec tor from which the rubber cable guide has been cut Terminal 5 should be sol dered to pin 1 of the XLR connector terminal 6 to pin 3 and finally termi nal 7 to pin 2 Before applying a little glue to keep the USB cable in place and to close the XLR connector again test the set up by connecting it to your computer When the new USB device is inserted for the first time you will be asked to install the drivers provided in the zip file 060012 11 zip Figure 5 Once the drivers are installed connect the XLR plug to your DMX512 equipment and launch the program cpp test bin test_cpp exe which is found in the same archive file There you have it Internet links Software environment PIC firmware The assembly code of the PIC is derived from version 1 25 of the firmware provided on Microchip s website the manufacturer of the PIC16C745 We used version 1 25 because version 2 00 did not seem to function with the erasable PICs we had available The file usb_main asm contains an endless loop reading batches of2. Unfortunately the copyrights for the driver source code rest with the author hence this file cannot be made freely available The pre programmed PIC order code 060129 41 is however available from Housed inside an XLR connector 13 Data Bus 8 EPROM Program Counter Program Memory 8 Level Stack 8K x 14 13 bit Program 14 RAM File Registers 256 x 8 Bus RAM Addr 1 9 Addr MUX 1 Indirect Addr Instruction reg Direct Addr 7 FSRreg K5 none kX STATUS reg K Power up V Timer Oscillator Start up Timer Instruction Decode amp Control Power on OSC1 Reset CLKIN Timing Watchdog Generation Timer OSC2 x4 PLL Brown out CLKOUT Reset Ld MCLR VDD Vss Parallel Slave Port TimerO Timer1 Timer2 8 bit A D re RAO ANO RA1 AN1 RA2 AN2 RA3 AN3 VREF RA4 TOCKI RA5 AN4 RBO INT RB lt 7 1 gt RCO T10SO T1CKI RC1 T10SI CCP2 RC2 CCP1 RC6 TX CK RC7 RX DT RD3 0 PSP3 0 RD4 PSP4 RD5 PSP5 RD6 PSP6 RD7 PSP7 REO AN5 RD RE1 AN6 WR RE2 AN7 CS A tt tt if
3. V pad terminal 4 the red wire to the 5V pad terminal 1 the green wire to the D pad termi nal 3 and finally the white wire to the D pad terminal 2 You ll find that this bit of the construction requires some dexterity in handling the solder iron ah Jibs rela r eg ies ee Erbil relied er lel ie SC Ce ie m ame T prde Fi ils Fi ils eh ihe relra reeled La I Erai T ee _YH Hi rh Erbil rera ela j ea Cf a Boe k mk rinm ralean ee Talp eed mb Erbil rele rr ee ek er Hire rel rae eo ee ced mb Erbil rel rae ee ee cd H e Hem ee eer i ed SC eg A i er Mieke rel rae ere ee ed lee 2 y ee 4H H7 Figure 7 The purpose of the oGenlnt sys driver function is to shape the requests sent by the USB bus LETETTE Labrie het eck Cet ApHitan tea doce A malali be logii pou Oat USE bo eS e Si un OD d installation ou une disquette a hound avec voire ploiph sique ineinezte eben errant Ques Hebe wouer eua que Arta eue 7 T pHa be ppn aulonsiquesend recomemand TE pstaler amp pestis dure linte ou dun emplacement upio ute eae pi Dipus pur Durani pau cinis i Nouveau mat riel d tect x Votre nouveau mat riel ect Install et pret lemplo Figure 5 If you are used to installing USB peripherals this type of screen should look familiar wir Inferfece sebop i Contrada External Control Preferences Figure 8 Settings screen in FreeStyler
4. data sent by the computer These data are utilised in the dmx512 asm file that synchro nises the USB reception with the trans mission on the serial DMX512 bus Also in this file we find the code that serves to generate the pause required at the end of each DMX field The test_cpp exe program This program shown in action in Fig Author s website http www oksidizer com http membres lycos fr epatix dmx_5 12 htm http users pandora be freestylerdmx http www beyondlogic org usbnutshell http ogloton free fr dmx_5 12 index html 74 ure 6 is used to quickly test the oper ation of the USB DMX512 converter Its source code demonstrates the way to use the unique function exported from DLL DasHard dll The really important bits happen in the test_cppDlg cpp file More specif ically the CTest_cppDlg OnVScroll function copies the value of the cur sors in the OutDmx output buffer And the CTest_cppDlg OnTimer function called on at regular inter vals loads the DLL and obtains a pointer on the OksidCommand func tion during its first call During the fol lowing calls it simply passes the out put buffer to the OksidCommand function The DLL DasHard dll This one links it all to the driver and provided a converter is connected to the computer opens a data stream with it This stream is fed by a specific thread that loops as long as the DLL is used Refer to the source code for more details The o
5. the Elektor SHOP on the web or in this I iji magazine cope ccPt USART ORAM ke Ey n 64x8 D Note 1 Higher order bits are from the STATUS register 2 Not available on PIC16C745 060012 12 Circuit diagram A quick look at the diagram in Fig ure 2 allows you to better understand why the circuit can be so compact it has only two active components The PIC16C745 IC2 in its 28 pin SMD SOIC version is clocked at 6 MHz by X1 a miniature resonator with inte grated capacitors The internal micro controller frequency is set to 24 MHz thanks to its integrated PLL thus lowering any risk of stray radiation which might occur when using a res onator at this frequency The PIC gen erates the 3 3 V voltage necessary on 1 5 kW SMD resistor R1 connected to Figure 1 PIC16C745 architecture RB6 the D line of the USB cable A 220 nF RBS AAOCREK SMD capacitor C2 smoothes this RB4 DS751 6BM voltage supplied directly by the hi microcontroller pin Pins D and D RB1 of the PIC are directly connected to aL the USB bus The second capacitor ba C1 is included to suppress fluctua ayy tions in the 5 volt supply voltage RAS caused by PIC switching The last aa A RA1 electronic component in the circuit RAO mm IC1 is an RS485 bus driver for which we use the SMD SO8 package ver sion It is connected to the USART Universal Synchronous amp Asynchr
6. Genilnt sys driver The driver see the screenshot in Fig ure 7 of which the source code is regrettably not available is in charge of shaping Control type requests trav eling on the USB bus The OGENINT INF file makes the driver installation possible It creates the association between the driver with our USB module thanks to the Vendor ID and Product ID identifiers that are specific to our application Freestyler free DMX512 driver software Freestyler is software written in Visual Basic that makes it possible to drive DMX512 equipment by indifferently using an impressive variety of convert ers for the parallel USB or Ethernet port As shown in the screenshot in Figure 8 the latest version also func tions with our circuit using the refer ence Oksidizer USB2DMX FreeStyler is available as a free download from the website run by the author of the program It comes with a complete user manual The screen copy in Figure 9 shows that FreeStyler offers a range of func tions that may disconcert a beginner but will be welcomed as very useful by DMX512 enlightened amateurs and professionals 060012 1 elektor electronics 9 2006
7. TSO msn USB DMX512 Co Jean Marc Lienher All amateur disc jockeys n and light jockeys dream ATS about it a DMX512 con verter not bigger than an XLR connector But at a retail price of 10 more than 500 pounds for this type of accessory the dream may never come true Here is a project that will make some on the dance floors very happy the DMX converter of their dreams and for only a few pounds The USB DMX512 converter described in this article connects to any com puter equipped with a USB connector and a Windows 98 OS or later The USB bus supplies the current neces sary to power the circuit we ve designed The proposed setup trans mits the 512 DMX channels at a rhythm of approximately 42 frames per second using a computer equipped with a USB 2 0 interface The maxi mum speed defined by the standard is 44 frames per second Note that this transmission rate may be a little less with a USB 1 0 connection The printed circuit board we designed for the con verter measures 14 mm by 26 mm and employs SMD components Important note our circuit like many DMX converters sold in retail shops 70 some of which come at exorbitant prices does not include full electrical isolation This is not terribly important when using a DMX device that s oper ating properly but could prove fatal for your computer if unfortunately a mains phase conductor of a defective projector or floodlight should come in
8. d thin gauge solder Start by IC1 DS75176BM National electronics co uk soldering the PIC micro IC2 into place be careful to observe the correct polar 72 elektor electronics 9 2006 ity which then constitutes a base plane in order to solder the compo nents on the other side of the circuit The best option so as to perfectly align the integrated circuit on the board is to apply a bit of solder to two pads for corner pins of the device Next place the PIC and reheat the two solder terminals in order to create an initial attachment point for the compo nent If the component is perfectly positioned the only thing left to do is to solder the remaining 26 pins If not reheat the corner pins and carefully re align the chip Next solder R1 and C2 on this side by pre tinning a pad then placing the component with tweezers while keep ing the pad at fusion temperature Po wwe obcehdiner com DM best app Figure 6 The test_cpp exe program is used for quick testing of our USB DMX512 converter 9 2006 elektor electronics Next solder the other connection of the component Use the same tech nique to solder the remaining compo nents IC1 C1 X1 on the other side of the board X1 is the component that requires the most attention because it is more usually soldered using the reflow technique Microsurgery Next we cut a USB type A A cable in half and strip it The black wire is sol dered to the 0
9. for the faint hearted 5 TONI 060012 1 piece of flatcable and a test clip for SOIC circuits The hex object code file to burn into the PIC is called Figure 4 The PIC occupies almost all space at one of the board sides firmware usb2dmx hex It is con This double sided board is through plated tained in archive file 060012 11 zip which may be downloaded free of charge from our website The PIC may also be purchased ready programmed from the Elektor SHOP Heat up your soldering irons Populating the board requires some skills handling SMD parts but should not cause dramatic problems Fortu nately the components used for this project are not as difficult to solder as for example an ARM processor in a BGA package with 278 balls sized 14 mm x 14 mm icond C OM PO N E NTS cz MC1EC74S 50 programmed 060012 41 LIST order code Miscellaneous Ki GMAHe resonadon M ra The printed circuit board of which the Resistor CSTCR6MO0G53 RO top and bottom side artwork is shown RI 1kQ5 0 25W 5 0805 XLR connector Cannon type 10HC089 in Figure 4 is without doubt one of the e g www distrelec com smallest we have ever published in Capacitors 12242 USB A A cable 8m Elektor Electronics C1 150nF ceramic 0603 standard C2 220nF ceramic 0603 PCB ref 060012 1 from The PCBshop ee Project software free download You need to use a soldering iron witha Semiconductors 060012 11 zip from www elektor fine tip an
10. o nous Receiver Transmitter of the 16C745 enabling it to be used bi 060012 11 Figure 2 The circuit diagram of our converter is limited in fact to a PIC micro and an RS485 bus driver 9 2006 elektor electronics 71 TSO msn directionally in case you would like to modify the firmware of the PIC to use it as a DMX512 input The non inverting buffer output of the RS485 driver is connected to pin 3 of the XLR connector and the inverter out put is connected to pin 2 since pin 1 is connected to ground As far as the USB cable and connector are con cerned this is a moulded cable sold in retail stores or the one with your old mouse USB of course It has four wires plus shielding a pair of untwisted fairly thick wires for the 5 V power supply voltage and two thinner wires twisted as pair for data transmission XLR connectors are supplied by many manufacturers Here a Cannon type 10HC089 is used It is important to use this XLR connector because a standard Neu trik connector does not have enough space to hold the circuit Programming the PIC The PIC 16C745 micro has to be pro grammed before soldering it onto the board If you re a home programmer make sure you have a suitable DIL to SOIC adaptor with your programmer Alternatively as we did in our tests see the photo in Figure 3 you can ie ei TUUT gt fe 3 9 A e i if y Va BOP make one yourself using a DIL carrier a Figure 3 Not
11. to contact with the DMX512 line Fore warned is forearmed A PIC16C745 The PIC16C745 of which the block dia gram can be found in Figure 1 is a low cost microcontroller However it was one of the first to have a USB interface In reality it is a type 1 1 low speed USB interface The transmission rate of the USB bus in low speed mode is 1 5 Mbits second The DMX512 bus speed is a measly 250 kbits s The USB is six times faster so where is the problem Well for one thing the USB standard defines two data trans fer modes for low speed Control transfer and Interrupt transfer The control mode uses all of the bus band width and is according to the stan dard reserved for USB receiver con figurations The Interrupt mode is intended for data transfer but we should note that it is limited to 800 bytes per second Out of spec With the above in mind we re more or less forced to use the 160745 in a con figuration that s not found in the USB elektor electronics 9 2006 nverter standard To do so we have selected the Control transfer mode in order to exchange data between the com puter and the microcontroller Obviously considering that the USB bus was not designed for that use we had to write a special driver for this Microsoft Windows appli cation The firmware source code for the microcontroller is available from our website at www elektor electronics co uk file 060129 11 zip
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