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6GHz+ Touchscreen Frequency & Period Counter This new Frequency Counter has greater bandwidth and more sensitivity than any previously published design and its large touchscreen display makes using it a breeze. Now we’ll describe how to assemble the two PCBs, test them, load the software and put the case together. I f you’ve read the first article on the Frequency Counter last month, you should have an idea of just how good its performance is and also a fairly thorough understanding of how it works. As the photos in that issue showed, it’s built using a PCB populated mainly with surface-mount devices (SMDs) plus a few RF connectors so it piggybacks onto the Explore 100, which in turn is plugged into a 5-inch fullcolour touchscreen LCD panel. We also showed the rather spiffylooking laser-cut clear acrylic case that it’s housed in on the last page of that article. So having explained all that in detail last month, we’re now going to go through the assembly procedure. It may seem a little daunting, as you have to build two separate PCBs and then assemble those two plus the pre-built LCD panel into a “sandwich” before building the box around it. Actually, besides a couple of fine84 Silicon Chip pitch SMD ICs, most of the components are relatively easy to work with and the Explore 100 module can be put together in just a couple of hours. The Frequency Counter board may take you a little longer but it isn’t too difficult and a reasonably experienced constructor can probably put it all together and get it working in one day. Having said that – don’t rush it! It’s far better to take your time, especially when working with SMDs, rather than risk damaging the PCB or any components. Even if you stuff something up, it’s generally possible to remove it, clean up the board and then try again. The assembly actually lends itself to being done in stages so you may prefer to spend a couple of hours at a time on it, then stop and move onto the next stage when you’re fresh. Assembly There are four main steps in putting together the 6GHz Touchscreen FreCelebrating 30 Years Part 2: by Nicholas Vinen quency Counter. You can do the first two steps in either order: assembling and testing the Micromite Plus Explore 100 module, and assembling the Frequency Counter PCB. Once those two are finished, you can plug them together and test the unit as a whole, before assembling the case around it. With the exception of the 5-inch LCD touchscreen, all the parts for the Explore 100 module are available as a short form kit from the Silicon Chip Online Shop. Note though that assembling this does involve soldering the 100-pin SMD PIC32 microcontroller. You can also get a slightly different version of the Explore 100 PCB with the SMDs, including the PIC32, presoldered from RicTech in New Zealand. This also comes with the other parts to fit yourself, in a similar fashion to the Silicon Chip short form kit. See www.rictech.nz/micromite-products for details. The circuit details of the Explore 100 module were published in the siliconchip.com.au September 2016 issue of Silicon Chip while the construction details were given in the October 2016 issue (see siliconchip.com.au/Series/304). We won't repeat them here, however, if you don't have that issue, the process is relatively straightforward. Briefly, you need to fit SMDs IC1 and Q1 first, being very careful to orientate them correctly and ensure that all the fillets are properly formed and no pins are shorted. Then solder the 10µF SMD capacitor in place, near IC1. Next, install the through-hole components as shown on the PCB silkscreen printing. These consist of nine resistors, 13 ceramic capacitors, two electrolytic capacitors, three LEDs, one crystal, one transistor, one regulator, one tactile switch and numerous connectors. The LED cathodes (shorter leads) go into the holes nearest the adjacent PCB edge. When fitting the connectors, make sure that CON6 and CON9 are fitted to the underside. You don't need to fit CON1, CON4, CON5, CON7, CON10, CON13, CON14 or the headers for the real-time clock. But if your kit comes with those parts anyway, it certainly won't hurt to install them. We do recommend that you fit JP1 as it will aid in testing. If you haven't used a pre-programmed PIC32 then the next step is to program it using a PICkit 3 or similar in-circuit serial programming (ICSP) tool. This is done via 6-pin header CON3. Then we suggest you test the board to make sure it's working before fitting the LCD panel. The easiest way to do this is to connect a USB/serial adaptor to CON6 and then open a terminal emulator, set to the default baud rate of 38400. Make sure the correct COM Port for your USB/serial adaptor is selected and then wire up its Tx, Rx and GND pins to the appropriate pins on CON6, making sure to wire Tx to Rx and vice versa. To power the unit, if your USB/serial adaptor has a 5V output, you can wire this to the bottom-most terminal of JP1 (if fitted). Alternatively, fit a jumper to JP1 and plug a mini USB cable from your PC to CON2. As soon as the unit has powered up, you should see the Micromite's banner appear on your terminal emulator. If you don't, disconnect power and recheck your wiring and COM port selection. Normal power consumption for siliconchip.com.au A couple of small errors to correct In writing this article, we found a couple of errors in part one, published last month. Firstly, CON1 is a PCB-mounting right-angle SMA connector, not SMD connector as stated in the parts list. Secondly, in the text at the end of page 28 and the start of page 29, it says that 32-bit timer 4/5 is used for the reference oscillator but as shown in Fig.1, it's actually timer 2/3. Similarly the previous reference to timer 2/3 in relation to the high-frequency input should have been timer 4/5. Also, the parts list called for four 6mm M3 machine screws but we found construction a little easier using two 8mm long machine screws instead. If you can't get these, you can still use 6mm but may need to attach the spacers in a slightly different order. Or as stated in the text, 10mm screws might work. the Explore 100 sans screen is around 100mA (at 5V). If yours is well under or over this, something is wrong, so check the PCB carefully for soldering defects and misplaced components. Assuming you've had success, remove power and plug the LCD screen into CON10, attaching it with four 12mm tapped spacers and eight machine screws. You will then need to power it up and run the following commands on the console, to set up and test the LCD. Note that power consumption will jump to several hundred milliamps. OPTION LCDPANEL SSD1963_5, LANDSCAPE, 48 OPTION TOUCH 1, 40, 39 GUI TEST LCDPANEL You should now see coloured circles being drawn on the screen. Press enter in your terminal emulator to stop, then run this command to calibrate the touch sensor: GUI CALIBRATE You will then need to use a thin object that will not scratch the screen, like a toothpick, to carefully press and hold in the centre of the targets which appear in each corner of the screen. Hopefully, you will get a message on the console that says "Done. No errors". Otherwise, try calibrating it again. That completes the initial setup of the Explore 100 module. Main PCB assembly There are many more SMDs on this board, plus a few through-hole components. Note though that the lead spacings of the components on the main board are, with one exception, much larger than those of IC1 on the Explore 100. Overall, you should find the components on this main board easier to solder. Celebrating 30 Years The main board is double-sided, coded 04110171 and measures 134 x 51.5mm. Almost all components are fitted on the top side. Start with IC4. You can use a standard soldering iron as long as the tip is not too large but we recommend that you purchase a small tube or syringe of flux paste and some solder wick if you don't already have some. Good light and a magnifier are also important. Place a small amount of solder on one of the corner pads for IC4 and then orientate the part on the board as shown in the PCB overlay diagram, Fig.3. Pin 1 goes towards upper left – this should be indicated on the PCB silkscreen. Once the IC is orientated correctly, heat the solder you applied to the corner pad and then carefully slide the IC into place and remove the heat. This process should take no more than a few seconds. Now carefully check that the IC pins are centred on their pads. Check all four sides. Use magnification to make sure that all pins are properly centred on their pads. If not, re-heat the solder on that one pad and gently nudge the IC towards the correct position. Repeat this process until you are happy that the IC is correctly located and check that its pin 1 is in the correct position before tack soldering the diagonally opposite pin. Re-check that all the pins are correctly located; you can re-heat either solder joint at this point to make slight adjustments. Now apply a thin layer of flux along all the IC pins and then apply solder to all the pins. Make sure you apply enough to get proper fillets. It's difficult to avoid bridging the pins at this point; what's most important is getting the solder to flow onto each pin and pad on the PCB. Once all the pins have been soldered, apply another thin layer of flux paste November 2017  85 Fig.3: use this PCB overlay diagram for the main Frequency Counter board as a guide during assembly. Most of the components are SMDs with the exceptions being RLY1, REG2 and the connectors. It plugs into the Micromite Plus Explore 100 module via CON3, a 2x20-pin female header socket that’s mounted on the underside of the board. CON3 and CON6 are the only components fitted to that side of the PCB. and then use a piece of solder wick to remove any excess solder, especially where adjacent pins are bridged. Proceed carefully and re-apply flux paste if necessary. Once you have finished, clean off the flux residue (using either a proper flux solvent or ethyl alcohol/methylated spirits and a lint-free cloth) and examine the solder joints under good light and magnification to ensure they are all good and there are no more bridges left. When you have completed soldering IC4, you can fit IC3 in the same manner. IC3 has smaller, more closelyspaced leads but there are only eight of them, four each on two sides of the IC. One additional thing you will have to take into consideration is that IC3 has a thermal pad on the underside and ideally, this should be soldered to the matching pad on the PCB. If you have a hot air reflow system this is quite easy, as it's just a matter of spreading some solder paste on the nine pads for this IC, putting it in position and then gently heating it until all the solder paste melts and reflows If you are just using a regular old soldering iron, you should spread a thin layer of solder paste on the large central pad, then drop the IC down into position and tack solder it in position. After checking that its orientation and position are correct, solder the remaining leads using the same technique as for IC4. Then flip the board over and squirt some flux paste into the hole directly under IC3. Melt some solder into this hole and heat it for several seconds. Remove heat and carefully check that IC3 is hot by quickly touching it with your finger. This indicates that the solder 86 Silicon Chip has conducted enough heat through the hole to melt the solder paste you placed under it earlier. Solder IC7 next. This is in a rather tiny 2 x 1.6mm metal can package but luckily it only has four pads, one in each corner. So soldering it is not that hard but identifying pin 1 requires significant magnification. You should be able to see a dot in one corner of the top surface and this goes to the lowerright pad. Tin one of the pads and flux the others, then heat the tinned pad while very carefully sliding it into place. Apply a small amount of solder the other three pads, then refresh the initial one and check with a magnifier that none of the joints is shorted to the can (solder shouldn’t stick easily to it). Note that there is provision for a micro USB power socket on the underside of the board but we haven’t tested this and we don’t recommend you use it, for two reasons. One, the output voltage of a USB charger is unlikely to be well-regulated and the LCD panel is quite fussy about its power quality. And two, there’s the possibility of RF noise getting back into the USB cable and producing a lot of EMI. Remaining SMDs The rest of the parts are quite easy to install as they have more widely spaced leads. Solder IC1 and IC2 next, making sure their “pointy” pins go to the pads marked for pin 1, facing the top edge of the board. Follow with L1 and L2, both of which are in six-pin packages. Their pin 1 dot should be orientated as shown in Fig.3, towards upper left. You can then move onto IC5, IC6, Celebrating 30 Years IC8 and IC9 which are all in standard 8-pin SOIC packages. These are quite easy to solder. Identify pin 1, indicated by either a dot/divot/logo in the corner or a bevelled edge on that side of the PCB. You can then orientate each IC as shown in Fig.3, tack down one pin and solder the others using a similar procedure as before. Next on the list are regulators REG1 and REG3. These are identical parts, each with one large tab and five smaller pins. The packages have considerable thermal inertia, so spread a thin layer of flux paste on the large pad with a little extra paste on the smaller pads and drop the part in position. Then, tack solder one of the smaller pins (you can pre-tin the pad and heat it while sliding the part into place, if you like, as you did with IC3). You can clean these joints up with some additional flux paste and an application of solder wick. Now for the large tab. Apply some solder to this tab and hold your iron in contact with both the regulator tab and PCB pad. You may need to hold it there for some time before the whole assembly heats up enough for the solder to flow down onto the board. Keep adding solder until the tab is covered and looks shiny, then remove the heat. Inductors L3 and L4 are similarly quite large, so again, spread flux paste on each of their pads before soldering. You can then add some solder to one of the pads and slide the inductor into place while heating that solder. Again, you may need to wait some time before the inductor heats up enough to slide fully into place and you can then add more solder until a nice, shiny fillet has formed. Let that cool down a little, then solder the siliconchip.com.au opposite end, again waiting until it's hot enough to form a good joint (this should be quicker as both the inductor and PCB will retain significant heat). The next components on the list are REF1, Q1 and diodes D4-D13. These are all in small 3-pin SOT-23 packages so don't get them mixed up. One of these diodes is a BAT54S (D12) while the others are all BAV99s. In each case, tack solder one pin, check that the pins are properly aligned, solder the other two pins and then refresh the initial pin. It's easier if you spread a little flux paste on the pads before soldering each part. Now fit diodes D1 and D2, which are in similar but slightly smaller packages than D4-D11, followed by diode D3, which is in a two-pin rectangular package. Make sure its cathode stripe faces towards REG2 (indicated with a “k” on the PCB). You can then fit all the ceramic capacitors and resistors to the board, as well as SMD ferrite bead FB1, where shown in Fig.3. Orientation is not critical for any of these. Note that some of the ceramic capacitors are in slightly smaller 2.0 x 1.2mm packages, compared to the majority of capacitors and resistors which are in 3.2 x 1.6mm packages, but these are not much more difficult to solder. Also, one of the resistors is a much larger 1W type but the procedure to mount this one is pretty much the same as the others. It just might take a bit more heat and flux paste. Through-hole components With all the SMDs in place, you can now proceed to solder reed relay RLY1 in place. It’s in a DIL package, like an IC but without pins in the middle section. Ensure its pin 1 indicator is towards the top of the board, as shown in Fig.3. Next on the list is REG2 which is in a TO-220 package that’s mounted flat on the board with a small flag heatsink. This is important since it needs to deliver several hundred milliamps and it can get quite hot. Bend its leads down so they fit the pads with its mounting hole correctly located, then place the heatsink underneath and screw the whole assembly firmly to the PCB. You can then check that the regulator’s package is straight before soldering and trimming the three pins. Solder the electrolytic capacitor in next, being careful to feed the longer siliconchip.com.au This photo shows the Frequency Counter PCB mounted on top of the Explore 100. They are held together by CON3 and CON6 at this stage. The LCD screen has not been plugged into the bottom of the Explore 100 yet. (+) lead through the hole marked “+” on the PCB, closest to REG2. The next component to fit is pin header CON3. CON3 is a 40 pin DIL socket (2x20 pins) which is mounted on the underside of the board and plugs into the Explore 100. Make sure it’s pushed down fully onto the PCB and nice and straight before soldering, or else you may have trouble plugging it in later. Follow with 6-way standard pin header CON8 and link LK1, both of which go on the top side of the board. Now mount SMA connector CON1, barrel connector CON5 and BNC sockets CON2 and CON7. In each case, ensure the part is pushed down fully onto the PCB before soldering the pins. The larger metal connectors such as CON1 require quite a bit of heat to form good solder joints. Note that the pads for CON1 are designed to allow either a right-angle or edge-mounting (“end launch”) connector. However, we recommend using a right-angle connector like we did in our prototype so that it lines up with the BNC sockets Finally, solder CON6 in place. This is a female header socket with long pins. The socket portion goes on the underside of the board, with the pins sticking through the top (see photos). This way, it plugs into the standard header already on the Explore 100 board and allows you to reprogram the PIC32 without having to remove the Frequency Counter board. It also helps to hold them together so don’t leave it off. Celebrating 30 Years GPS module wiring You don’t need to connect a GPS module but it improves accuracy and doesn’t add terribly to the cost of building the unit, so we expect most constructors will do so. If you’re using the recommended VK2828U7G5LF module, it’s supplied with a short sixwire cable with a small plug at one end that goes into a socket on the GPS module itself. The wires are colour coded yellow (enable), black (ground), green (Rx), blue (Tx), red (Vcc) and white (1PPS). Crimp and solder these wires to the pins supplied with the 6-way polarised plug, then insert them in the same order as they are listed above. Because the plug is polarised, you will need to ensure you start inserting them from the correct end of the plug housing. It’s simply a matter of lining this housing up with the socket on the PCB, checking which end is labelled EN and then insert the pin soldered to the yellow wire into that end of the plug housing, followed by the others in sequence. Push each one in with a small screwdriver until it clicks into place. The next step is to select the GPS module operating voltage by bridging two of the three pins on LK1 with a shorting block. For the VK2828U7G5LF, use the 3.3V setting, bridging the pins indicated on Fig.3 or the PCB silkscreen. This actually powers the module from the 3.4V rail, which is good, since 3.3V is the minimum VCC specificaNovember 2017  87 right-most button in the toolbar at the top of the window, with an icon that looks like a blue stick figure running while holding a torch. You should then see a progress dialog and the upload will take a minute or so. If it fails, close this window and re-check the COM port settings. Once the upload is complete, the MMChat console window will automatically appear. Type “OPTION AUTORUN ON” into the text entry window at the top and press enter. This will cause the software to run each time power is applied. You can then type “RUN” to start it. However, it will not work properly yet because the Frequency Counter board has not been plugged in. This will allow you to check that the software has been loaded, though. Initial testing The LCD screen fits through a large rectangular cut-out in the front of the case, sitting almost flush with its surface. A notch in this cut-out is provided for the ribbon cable at lower right. You can also clearly see how the top panel of the case is recessed to give access to the power, input and output connectors. tion for this module and the extra 0.1V gives us a small safety margin. If using a different module, check its data sheet. Most modules will run from either 3.3V or 5V (or both). Make sure your module uses TTL serial signalling at 9600 baud and it will need a 1PPS output to work with this project. Also, check the data sheet to determine the pinout and route the correct wires to the plug. Some modules may not have an enable pin, or they may allow you to leave the enable pin disconnected for normal operation. The VK2828U7G5LF uses an active-high enable signal so if your module requires an active-low enable signal, you will have to wire it to GND. You don’t need to plug the GPS unit in straight away; it may be a good idea to check the unit works first, then switch off and plug it in later before checking the GPS-specific functions. Loading the software The recommended Explore 100 kit comes with a pre-programmed microcontroller. This is loaded with MMBasic but does not have the BASIC (and C) code required for the frequency counter loaded into it yet. Luckily, 88 Silicon Chip since we have already used the serial console to test the unit and set up the LCD, we can use this to load the software into the chip too. The easiest way to do this is to download the free MMEdit software which is specifically designed to interface with Micromites. This will run on Windows or Linux machines and is available from www.c-com.com.au/ MMedit.htm As well as downloading and installing this program, you will also need to download the BASIC code from the Silicon Chip website. This is free for subscribers and it’s also available to those who have purchased the Frequency Counter PCB. Extract the .BAS file and open it in MMEdit. Open the Advanced menu and make sure the “Auto crunch on load” option is selected. You then need to set up the COM port. Make sure you’ve closed the terminal emulator you were using before, to free up the port, then select the “New...” option in the Connect menu and select the relevant port. Set the baud rate to the default of 38,400. You can then click on the “Load and run current code” button which is the Celebrating 30 Years Before plugging the Frequency Counter PCB into the Explore 100 (which by now you should have tested on its own), we should do some basic checks to the Frequency Counter addon board. The first check is to measure the power consumption and check that all the supply rails are within the expected ranges. It’s best to perform these checks with the GPS module initially disconnected. The expected current drain for this board by itself is around 500mA so if you have a bench supply, set its current limit somewhere between 500mA and 1A. If you don’t have a bench supply, connect a DMM set to measure amps in series with a 6V DC regulated plugpack. If that’s too hard, you can simply skip this step and just check the voltages. With power applied, connect a DMM set to measure volts between the GND and 5V test points at lower left. You should get a reading between 4.8V and 5.2V. If it’s outside that range, switch off and check for faults. A much lower reading suggests a short circuit or incorrectly orientated component somewhere on the PCB (eg, D3) while a higher reading should not be possible and suggests that REG2 has failed. Now measure between GND and the 3.4V test point. You should get a reading between 3.3V and 3.45V. Again, a low reading would suggest a short circuit, most likely associated with IC1, IC2 or IC4 but could also be caused by a problem with REG1 or one of its associated components. A high readsiliconchip.com.au ing would suggest a fault with REG1. The reading at the 2.5V test point should be in the range of 2.475-2.575V with a low reading likely indicating a soldering fault with IC7, the temperature-controlled crystal oscillator. A high reading would indicate a likely fault with REG3. The measurement at the 1.4V test point should be around 1.41-1.44V with a low reading suggesting a problem with the 300W and 390W resistors located just above IC4 or one of the components surrounding REF1. A high reading suggests a fault with REF1 itself, or a soldering problem with it or one of the adjacent resistors. Assuming that all checks out, you can power it down and plug the GPS module back in (assuming you’re using one). Make sure LK1 is set properly, power the unit back up and check that the power consumption has only gone up by about 50mA and that the 5V and 3.4V rails have not dropped significantly, which would indicate a wiring problem with the module. You can now power the PCB down and plug it into the Explore 100 board. Make sure to power the whole assembly through the DC power socket on the Frequency Meter board since the regulator on the Explore 100 is unlikely to cope with the extra current drawn by the combination. More advanced testing It’s probably a good idea to put the unit through its paces now before it’s in the case. While you can quite easily change the software once it’s in SILICON CHIP This rear view of the completed unit shows how the case is put together. Both the front and rear panels are attached to two points at the bottom of the Explore 100 PCB. the case (eg, if a bug is discovered or there’s an upgrade), fixing any hardware issues would probably require you to partly disassemble the case. It wouldn’t be a disaster but it’s easier to test it at this stage. The first thing to do is power it up and check that the display comes up and updates properly. Power consumption of the complete unit should be very close to 1A so verify that if you can. Then check the upper-left hand corner of the screen and make sure that ONLINESHOP you have a sensible TCXO frequency reading (close to 16.368MHz). If you have a GPS unit fitted, you should be able to see the reflection of its status LEDs at the rear of the unit. For the VK2828U7G5LF, red indicates power and green flashes indicate satellite lock. Place the unit somewhere where it has a good view of the sky (eg, on a windowsill) and wait a few minutes. You should see green flashes from the GPS unit and the top-right corner of the screen will update to show the . . . it’s the shop that never closes! 24 hours a day, 7 days a week . . . it’s the shop that has all recent SILICON CHIP PCBs – in stock . . . it’s the shop that has those hard-to-get bits for S ILICON C HIP projects . . . it’s the shop that has all titles in the SILICON C HIP library available! . . . it’s the shop where you can place an order for a subscription (printed or on-line) from anywhere in the world! . . . it’s the shop where you can pay on line, by email, by mail or by phone Browse online now at www.siliconchip.com.au/shop siliconchip.com.au Celebrating 30 Years November 2017  89 time, date, number of satellites, your location and give a flashing green circle pulsing at 1Hz, in time with the 1pps signal from the GPS unit. You can now connect a signal source with a known frequency to the two inputs at the left side of the unit and verify that you get sensible readings. That will verify that pretty much all the functions of the unit are working properly. We’ll go into more details of the software operation next month. Case assembly The case is made up of six pieces of clear 3mm laser-cut acrylic, forming the front, back, top, bottom and side panels. Peel off the protective coating from each piece as you assemble the case. You will need to remove the screws from both ends of each space between the Explore 100 board and the LCD panel before you can proceed. Use Fig.4 as a guide to help you with the following assembly procedure. Start with the front panel, which has the large cut-out for the LCD. Try to avoid bending it too much since it could potentially snap. This has a small notch for the LCD ribbon cable to fit through, so figure out which way around it goes using this notch. Now feed a 32mm M3 machine screw through one of the two lower corner holes in the front of the panel and do up a Nylon hex nut tight, holding the screw in place. Repeat for the other lower corner. Attach 10mm machine screws to the other two (top) mounting holes in a similar manner and hold in place using Nylon nuts. Now unplug the LCD from the Explore 100 and feed the screen through the hole on this panel, then screw the original 12mm spacers onto each screw shaft until it’s holding the LCD in place firmly in all four corners. You can then plug the Explore 100 board back into the LCD panel after feeding the protruding screw shafts through its mounting holes. Use two 8mm machine screws to attach it to the two top spacers and screw two Nylon hex nuts onto the two remaining screw shafts after placing Nylon washers under each. Do them up tightly. Next, feed two 6mm or 8mm M3 machine screws through the two mounting holes on the main Frequency Counter board from the underside and attach them using Nylon nuts and washers, done up well. 90 Silicon Chip Fig.4: this diagram shows the view looking into the left-hand side of the unit and clarifies how the various screws, spacers and washers hold the case together. The side, top and bottom panels are held in place by the front and rear panels. Note that if you can’t get 8mm machine screws, you may be able to get away with 10mm screws. You can also use 6mm screws (which are also commonly available) but you may need to reverse the order of spacers in the last step. The next step is to feed the two 25mm tapped spacers over the screw shafts in the lower part of the assembly. Once those are done up, you can place the rear panel on top of the spacers and check that the 3mm holes line up properly. If you’re wiring up the GPS module, now is a good time to attach it to the rear panel using double-sided tape and plug it into its header. There should be just enough room in the case with the rear panel fitted for the connector. Make sure you tape the GPS receiver in a position where it won’t foul any other components. We recommend that it’s fitted near the top of the case for better signal reception. Now remove the nuts and washers from the BNC connectors and then slot the tabs of the top panel into the front Celebrating 30 Years and rear panels. Do the BNC connector nuts back up loosely (with the washers underneath) to hold the top panel in place. The bottom panel is held in similarly, between the front and rear panels. Orientate it so that the small cut-out gives access to the serial header pins. Now it’s just a matter of slotting the left and right panels into the holes in the front and rear panels and over the tabs on the top and bottom panels. The only difference between the left and right panels is that the left panel has a cut-out to access the mini USB socket. With all the panels in place, feed the four 10mm M3 machine screws through the holes in the rear panel and do them up loosely. Then, having checked that all panels are properly positioned, do them up properly and tighten up the BNC socket nuts. Conclusion That’s all we have space for this month. In the next and final instalment, we will show screen grabs of the unit in operation and explain how to use it. SC siliconchip.com.au