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High-visibility 6-digit LED GPS clock; Pt.2 Last month we introduced our GPS high-visibility 6-digit LED clock. But we should emphasise its main feature: it automatically changes time zones as you travel around the country; important if you are cruising the world on a yacht or just touring around the country. This second article gives all the info to build and use the clock. W E’RE VERY pleased with this clock because its big, bright display is so eye-catching and can be viewed from quite some distance away. It also has quite a few features beyond just displaying the time, as will become apparent when you read the operating instructions below. Last month, we mentioned that you can use a module with RS-232 signalling but that TTL is preferred. Modules with RS-232 signalling have a bipolar voltage swing on their serial port pins of between ±3V and ±15V. This allows longer cable runs and improves noise immunity. But with the module only a few centimetres away from the microcontrol36  Silicon Chip ler this is unnecessary and only complicates interfacing. As a result, many GPS modules simply use a 0-3.3V (or thereabouts) swing, ie, TTL levels and the signals are inverted too. You may get a better deal on an RS232 module and in this case you can simply wire a resistor of say 4.7kΩ10kΩ between the GPS module’s TX line and the clock’s RX pin. The microcontroller’s internal clamp diodes will then limit the applied voltage to a safe level. This works despite the signal inversion because if the clock detects gibberish from the GPS module, it tries inverting the signal level. If that doesn’t work, it will also try various baud rates from 2400 bps up to 115,200 bps with both inverted and non-inverted sense until it detects valid NMEA data. The most common rates of 4800 and 9600 baud are tried first. By the way, GPS modules are now becoming available with GLONASS support. GLONASS is a GPS competitor built by Russia and modules which support this will typically work better indoors or in poor signal areas because they have access to more satellites – in other words, they can use both GPS and GLONASS satellites to get a fix. Last month we mentioned that the u-blox Neo-6M is available for around US$10.42 but you might also want to consider the Neo-7M for around $20 siliconchip.com.au Scale: 1mm on diagram = 3mm (⅓ actual size) 341mm Top (rear) (bottom) Left Back 217mm (rear) (rear) Bottom (rear) Front By Nicholas Vinen Right (bottom) Fig.4: this diagram shows how the single sheet of 350 x 225mm (or larger) acrylic is cut up into the six large pieces and six smaller pieces that are then glued together to form the case. Cutting takes about five minutes. The case includes slots for wall-hanging and some holes to make the piezo sound louder. for the presence of the 32kHz signal on pin 11 of IC1. If that’s missing, it may be that one of the leads of crystal X1 is shorted to the case or some other adjacent metalwork. If a GPS module is detected, the unit will indicate that it is waiting for a position fix by showing “GPS” on the display, along with a progress display. Otherwise, the clock will flash “12:00:00” until you set the date and time (see below for information on how to do this). Assuming it’s working, you can move on to making the case. Assembling the case Fig.5: the front of the case with the left and right panels already in place and the top and bottom about to be glued. The red shaded areas show where adhesive would need to be applied for the top panel to be glued although as stated in the text, you could apply adhesive to only the top piece as long it’s applied to all the faces that will contact the shaded ones. Note carefully the hole positions in the four surrounding panels so that you glue them with the correct configuration. which is very similar to the 6M but also has GLONASS support. We should point out that like most other modules, both the Neo-6M and Neo-7M come with ceramic patch antennas but these are external antennas connected via a short cable. This means you could in theory connect it to a larger external antenna. Testing There isn’t much to testing the clock. The simplest method is to power it up briefly. There might be a short siliconchip.com.au delay (of no more than a few seconds) while the supercap charges up but it should then immediately perform a display test where each segment on all the digits lights up in turn and then the piezo buzzer will sound a 100ms beep. If that doesn’t happen after a few seconds, switch off and check for faults such as incorrectly installed components or bad solder joints. You can also check that the output voltages of REG1, REG2 and REG3 are correct. After the test procedure, IC1 will fire up its 32kHz oscillator. If you get the digit test but nothing else, check The case is made from a single piece of clear or tinted acrylic which starts out at 350 x 225mm and is laser-cut into six large pieces plus a number of smaller pieces, which are then glued together. The back is not glued on; it’s held with four self-tapping screws so that it can be removed to allow access to the PCB module for maintenance. The cutting pattern is shown in Fig.4. If you have a laser cutter, or access to one, you can download this pattern from the SILICON CHIP website in DXF or SVG format (free for subscribers) and cut it yourself. With a 50W laser, we used settings of 8mm/second at 80% power. We can also supply precut case kits from our online shop, together with the PCBs, programmed microcontrollers and some of the 7-segment displays. You can use clear acrylic, as shown January 2016  37 This view shows the completed clock PCB from the rear. The PCB is held in position by the two small centre pieces that mount at right angles to the rear panel (see Fig.6). on our prototype or acrylic tinted with a colour that matches the displays (ie, green, blue, red, etc). You will see more of the workings of the clock with the clear case but the tinted case may provide better contrast for the display. The clear case is suited to any display colour whereas a tinted case will need to match the display colour used. The case is glued using a special solvent-based adhesive that makes very strong bonds between pieces of acrylic. You could use cyanoacrylate (super glue) in a pinch but we can’t guarantee that the result would last. We used SciGrip Weld-On 16, fastsetting “clear, medium-bodied solvent cement”. It states on the label that it’s suited for Butyrate, Polycarbonate, Styrene and Acrylics. You are unlikely to find this type of adhesive in a hardware store but should be able to get it from a plastic supplier. Ours came from Plastix [Sydney: (02) 9567 4261, Northern Beaches: (02) 9939 0555]. This forms a strong bond quickly so you have about a minute to apply the adhesive to the pieces to be mated, press them together and get them lined up properly. Full strength is achieved after about 24 hours however it sets well enough to manipulate the pieces after about 10-15 minutes. The bond is clear but you don’t want to get excess adhesive on the material as it will affect the surface finish and you definitely don’t want to drip it on the front face. It tends to get a bit “stringy” (sort of like melted mozzarella) after coming on contact with the 38  Silicon Chip acrylic. Keep a clean (disposable) rag on hand to mop up any excess adhesive. Also make sure you have a large, clean, flat surface to lay the pieces down on, eg, lay down some sheets of plain paper on your workbench. Gluing the pieces The front section (ie, where the display will be seen) can be identified by the four 5mm holes for the colon LEDs. Four more sections are glued to this to form an open box. These sections must be fitted with a specific orientation so before gluing them, put them together loosely to make sure you have the right pieces and understand the required orientations. Start the assembly by gluing the top, bottom and side pieces to the front panel as shown in Fig.5. Note that the front panel does not have mirror symmetry, so be sure to orientate it so that the LED colons will slant in the correct direction. The other pieces can then be laid out around the front panel in the correct orientations before you start gluing any pieces. That done, start with one of the smaller left or right end panels. When gluing these pieces, you will need to coat all the mating surfaces with a decent amount of adhesive to make sure the bonds are good. An example is shown in Fig.5 for gluing the top panel; the areas shaded red are where adhesive would need to be applied, assuming the left and right panels were already in place. Note that you could coat just the sur- faces of the panel being introduced to the assembly each time – you would need to apply adhesive to this which would mate with the red surfaces shown on the other pieces (which would have been difficult to depict from this angle). Glue the first panel, then wait a few minutes for the adhesive to make a decent bond before moving on to one of the adjoining panels. Repeat until all four sides are in place, then quickly drop the rear panel into place (being careful not to get any glue on it) to check that everything is nice and square and nothing will foul the rear panel once the adhesive finishes curing. The next step is to glue six small pieces to the rear panel, as shown in Fig.6. The trick is to use enough adhesive to give a good strong bond without the excess spreading out too much. You also need to be careful to make sure each piece is glued exactly perpendicular to the rear panel. Check that the four pieces which have holes in them are not angled out towards the edge of the panel as they must slot inside the top and bottom pieces of the case. You can check this once the six pieces are in place and the adhesive has started to set; gently drop the rear panel into place and then remove to set. It’s best to leave the pieces overnight so the bonds achieve full strength. You can then introduce the PCB assembly into the case. Hold it at an angle and slide the DC socket and pushbutton siliconchip.com.au Fig.6: the six smaller pieces are glued into the rear panel. Be sure to use sufficient adhesive to form strong bonds. The four upper & lower pieces with holes are used to hold the back onto the case and by extension hold the case and whole assembly to the wall. The two smaller pieces glued in the middle press the PCB assembly up against the front of the case. The rear panel is symmetrical so the parts can be glued to either side as long as they’re all on the same side. into one side of the case, then rotate it until the 7-segment displays rest on the inside of the front panel. The rear panel can then be attached using four 4GA self-tapping screws through the holes in the top and bottom that bite into the parts glued into the rear panel earlier. The basic idea is shown in Fig.7. For desk use, fit a small rubber foot to each corner at the bottom. For wall mounting, two screws placed 200mm apart will fit into the slots on the back. The heads must be between 4mm and 9.5mm in diameter. Most small wood screws should fit; check before screwing them into the wall. Don’t hang it until the adhesive has achieved full strength. LDR calibration Once the unit is in place and powered up, calibrating the LDR is simple. Shine a bright light on the LDR for a few seconds (eg, a torch), then cover the unit up for a few seconds (eg, with a pillow case) to block out all light – or simply place it in a dark room and turn the lights off. The unit will automatically record the highest and lowest values read and adjust its calibration to suit. GPS time acquisition If there is no GPS module fitted, by default the unit will power up showing a flashing “12:00:00” display, waiting for the time and date to be set, as explained below. However, if a GPS unit is detected, the display will change to siliconchip.com.au Fig.7: this shows the two halves of the case being put together; machine screws are shown however we recommend you use No.4 self-tapping screws. Be gentle when cutting the threads initially; if any of the smaller pieces break off during this process you will have to re-glue them and wait for the adhesive to set again. “GPS 00”. As satellites are picked up, the number will be updated to show how many are “seen”. If the unit has a 1PPS output, the decimal point after “GPS” will flash in time with it, until a GPS lock is acquired. Once the unit has a GPS fix (latitute/ longitude), the display will change to “GPS FI”. It will then wait to receive valid date/time information, at which point the display will change to “GPS SE” as it searches for valid time zone data based on that information. Once the data is found, the display will change to show the local time. If GPS fix is lost, the unit will fall back on its 32.768kHz crystal for timekeeping. After several minutes, the display will start pulsating (ie, varying in brightness over time) to indicate that it is no longer 100% accurate. If a GPS fix is re-acquired, the time is updated and it stops pulsating. Setting up the IR remote By default, the clock is set to respond to infrared remote commands from an Altronics/DynaLink A1012 learning remote on TV code 170. The default mapping is shown in Fig.8. The various functions indicated are described below. We’ve chosen this remote because it’s relatively inexpensive, easy to get, looks good and has all the buttons needed for this project. Having said that, just about any universal remote control can be used, including Jaycar’s Cat. AR1719. Whichever remote you use, it just January 2016  39 ESCAPE/ EXIT MENU SHOW DATE ESCAPE DATED CNTUP START TIMER (COUNT UP) START TIMER (COUNT DOWN) CNTDN ENTER MENU, SELECT ITEM TV SAT CD VCR DVD AUX 1 2 3 4 5 6 7 8 9 AV 0 -/-- + − CH SET VOL + − ENTER TIMES & NUMBERS NUM NUM NUM NUM NUM 0, 2, 4, 6, 8, NUM NUM NUM NUM NUM 1, 3, 5, 7, 9 ADJUST BRIGHTNESS BRI UP, BRI DN NAVIGATE MENU, MOVE CURSOR UP, DOWN, LEFT, RIGHT SELECT OK LEARN MENU ALA ON TURN ALARMS ON/OFF TIMER PAUSE TIPAU DISPON DISPLAY ON/OFF EXIT TIMER LOSE ONE MINUTE TISUB TIMER SPLIT/LAP TILAP TIMER ADD ONE MINUTE TIADD TIMER RESUME TIRES DYNALINK LINK Fig.8: the default button mapping on the Altronics DynaLink A1012 remote control set to TV code 170. Other remotes can be used but you may have to program the button codes into the clock, as described in the text. If so, use this as a guide as to which buttons to map to which functions. The button function names displayed on the clock during set-up are shown in blue on this diagram. needs to be set up to produce Philips RC5 or NEC-compatible infrared commands. To check this, point the remote at the clock and press the buttons. You may need to guess at some appropriate code settings first (eg, Philips TVs). Check the manual supplied with the remote. If it’s producing commands that the clock can receive, the last decimal point on the display will flash. While many different modes will produce some valid commands, you may need to try several different codes before you find one where all the buttons you need actually work. Refer to Fig.8 for guidance but note that the button mapping for your remote doesn’t need to match exactly (ie, your remote may not have an identical button layout). 40  Silicon Chip Once you have decided which remote to use and the setting to use it on, power up the clock and put it in IR set-up mode by holding down the buttons on either side of the clock simultaneously for several seconds. The display will show “IR SET”. Release the buttons, then press the right-side button to continue. The display will flash “NUM 0”, indicating the button code that is to be set. Hold down the “0” button on your remote control for a second or two. It will then briefly show the remote code received and then the display will switch to flashing “NUM 1”. Repeat this procedure for the remaining buttons. The codes corresponding to each button are shown in Fig.8. If at any point you make a mistake, you can go back and reset the previous button code by pressing the lefthand pushbutton on the clock. If you don’t want to assign a button to an IR code, press the righthand pushbutton to skip that one. Once you have set all the codes, “IR FIN” will be shown. You can then press the right-hand button on the clock to go back to normal operation or the left button if you need to change a code first. If necessary, buttons can be re-assigned later, using the “CHANGE” option in the “IR” menu. Menu operation is described below. Setting the time & date This is only necessary if you haven’t fitted a GPS module. Press the OK button on the remote control and then press the down button until the display shows “SETDA”. Press OK; the display will then show “010116” representing 1st January 2016 (assuming your date format is set to the default of DDMMYY). Use the keypad on the remote control to enter the correct date then press the select button. You can then go back into the menu and select “SETTI”. It will change to show “000000” representing midnight (HHMMSS). Check the current time, then enter what the time will be in a minute or two, in 24-hour notation using the keypad – but don’t put in the last digit yet. Do that the instant that the reference clock matches the time entered. This same procedure can be used to change the time or date at a later stage. Note that you can also use the up/ down/left/right arrows to change the time and date, however it’s easier to use the numeric buttons. If necessary, you can set the time and date without a remote; see the “Operating without a remote” section below. If you want the clock to make daylight saving time (DST) changes automatically without a GPS module, you will also need to tell it which time zone you are in. This can be done before or after setting the time. Press the OK button on the remote control and then press the down button until the display shows “SETTZ”. Press OK, then refer to Table 1 and choose the appropriate zone using the up/down. Press OK to confirm. The default is “NONE” in which case no time zone calculations are done. If a time zone is selected which has no DST rules (as per Table 1), this will not have any obvious effect, except that changing to a different time zone will then change the time to suit that location. If a time zone with daylight savings rules is selected, those rules will be obeyed and the clock will automatically change the displayed time when appropriate. It’s possible to override the DST rules, should they change after this article is published, or if an error is found; we explain how to do that later in this article. Showing the date Once set, the clock normally displays the time. The date can be shown with a quick press of either button on the clock itself or by pressing the show date button (usually mute) on the remote control. It will be displayed for five seconds with decimal points separating the day/month/year, then the unit will switch back to time display. Display brightness Hold down the volume+ or volume– buttons on the remote control to vary the display brightness. Auto-dimming continues to operate, if configured. For example, if you’ve set the brightness to 50% and the auto-dim is at 50% then the overall display brightness will be 25% of maximum. Menu system The time setting description above involved entering the menu to access the “SETDA”, “SETTI” and “SETTZ” options. The full menu tree is shown in Fig.9. The top level menu, shown in the blue boxes at the left, is acsiliconchip.com.au (Mon-Fri) (Sat,Sun) ALARM ALA ON global on/off OPTS MON TUE WED PM LZB 12/24 AM/PM Leading hour decimal zero mode point blanking select on/off DISP CHANGE Show received IR codes NUM 0 NUM 1 DISPON SETDA (no GPS) FRI SAT WD SUN WD WE WD ALL on/ set on/ set on/ set on/ set on/ set on/ set on/ set on/ set on/ set on/ set off off off off off off off off off off 24 HR IR THU COL DDMYY XTAL DIM Set colon on/off/ flash or decimal point on/flash Set date format 32kHz trim set BRIGHT LLIM Set IR code Set IR code Set IR code ULIM MINBR PIEZO Set manual brightness % Set LDR upper limit % Set LDR lower limit % Set dimming mininmum brightness % DURA HZ DUTY CADENC Set alarm buzzer duration Set alarm buzzer pulse rate Set alarm buzzer duty cycle Set alarm buzzer cadence Use up/down buttons to cycle through menu items; OK/Enter (SELECT) to descent into sub-menus or select current menu item; power/standby (ESCAPE) button to return to previous menu or exit. Set date CURTZ CHA TZ (GPS) TZNAM LATIT LONGIT N SAT OFFSET DAYDEL DAYRUL Show Show Show Show Show Show/set Show/set Show/set detected detected latitude longitude number time zone DST DST rules timezone timezone from GPS from GPS satellites offset in delta in (refer to ID name receiver receiver detected hh:mm minutes Table 1) SETTI (no GPS) Set time STAMO STAWE STADAY STA HR ENDMO ENDWE ENDDAY END HR DSMOD Set time Show/set Show/set Show/set Show/set Show/set Show/set Show/set Show/set Show/set DST DST DST DST DST DST DST DST DST zone start start start end end end end mode (from Table 1 start week day hour month week day hour or auto.) month CHADST (GPS) SETTZ Fig.9: this shows the complete menu tree for the clock. The main menu is shown in blue on the left; two of the options vary depending on whether a GPS module has been detected or not. Sub-menu options are shown in mauve with their sub-menus shown in green. Pressing the OK/select button activates the function indicated for each menu item, allowing that parameter to be viewed or set. The escape (on/off) button goes out of the current menu and back to the parent, or in the case of the main menu, back to the regular time display. cessed by pressing the OK button on the remote (or via the pushbuttons, as described later). Up and down scroll through the list. Each additional “level” of the menu is shown in a different colour and is accessed by pressing OK on its “parent” entry. Similarly, pressing the escape button (normally the power on/ off button on the remote) will take you back up to the parent menu or back to the time display, if viewing the top level menu. Below, we’ll go through the remaining menu items and explain what they do, as well as detailing other clock functions accessed by different buttons on the remote. Operating without a remote The menu system can also be accessed without a remote, using the pushbuttons on the unit. Hold down the right pushbutton for at least one siliconchip.com.au second and release it to enter the menu. Pressing the left button is then equivalent to the up button on the remote while pressing the right button is equivalent to down. These then let you scroll through the menus. To escape from a menu, hold down the left button for at least one second and release. To select an item, hold down the right pushbutton for at least one second and release. When you need to enter a numeric value (eg, setting the time), short presses of each button will increment or decrement the currently selected digit. Holding down the right button for at least one second will cycle to the next digit. Holding down the left button for at least one second will save changes and return to the previous menu item. Holding down both buttons together and then releasing will abort changing that value. In this manner, you can operate the menus without the remote. The buttons can also be used to show the date. However, note that many other functions are not available without a remote, such as timer modes and so on. Basically, the unit is designed to be used with a remote and the button functions are a fall-back, primarily intended for applications where it’s used purely as a clock. Setting the alarm Normally, the right-most decimal point on the clock shows the global alarm status. If on, the alarm is set to go off at least once in the coming week. It’s dim if there is no alarm set in the next 24 hours or bright if there is. To set the alarm, enter the ALARM menu. You will see either “ALA ON” or “ALAOFF”, indicating the global alarm on/off status. Press either OK or the record (ALA ON) button on the remote to toggle it. The ALA ON butJanuary 2016  41 Fig.10(a-d): this series of images shows the complete global land mass coverage of the time zone data programmed into the clock. There are 128 separate shaded areas, mapped to 73 different time zones, each with different UTC/GMT offsets and daylight savings rules. You can download the data from our website and map it onto Google Earth to inspect or modify it. Note that many zones overlap which has been done to reduce the compressed size of the data set; see text for more details. ton will also work when the clock is showing the time, as a quick and easy way to enable or disable the alarm. Cycle through the next seven menu entries to turn the alarm on or off for an individual day, or set the time for that day (in 24-hour format). The record button is used to toggle that day’s on/ off status while select can be pressed to set the alarm time, similarly to the way the clock’s own time is set as described above. You will also find menu entries for “WD” (weekdays), “WE” (weekend days) and “ALL”. Changing the on/off status or time for any of these entries affects multiple alarms, ie, Monday-Friday for “WD”, Saturday-Sunday for “WE” and MondaySunday for “ALL”. They can still be individually changed after that. When finished setting alarm times, keep pressing on/off to exit the menus and return to the clock display. When the alarm goes off, briefly press either pushbutton or the Escape button on the remote for a 5-minute snooze. A long (1s+) press of either pushbutton or a second press of the Escape button will cancel it altogether. Using the clock as a timer The clock can count time upwards starting at zero (eg, to measure how long something takes) or downwards to zero (eg, to alert you when a certain amount of time has passed). It also has stopwatch type functions such as a lap counter. It counts with 1/100th second resolution for times less than one hour, 1/10th second resolution up to 10 hours, one second resolution for up to 100 hours and with further 42  Silicon Chip reduced resolution up to 1000 days. Since infrared commands normally take the same amount of time to transmit, receive and decode, the timing should be pretty accurate, to within a few hundredths of a second. However, since there’s no guarantee an infrared command will be received without corruption, you will need to hold down the button to start the timer reliably which could result in it sometimes being off by a fraction of a second. There are three basic modes: count up with no limit, count up until a specific time is reached, or count down from a specific time to zero. When the limit is reached (either counting up or counting down), the piezo buzzer sounds, although this can be turned off if desired. Counting can be paused and the counter can have one minute added or subtracted while it’s running. Starting the timer Press the channel+ button and the timer will start counting up from zero. You can tell the timer and not the clock is running since the colon LEDs switch off and the decimal points flash instead. Press the pause button to pause the timer; the display will freeze and flash. Press the play button to resume. If you press the stop button, the display will freeze and flash but it will show the time for the last lap; ie, since the timer started for the first lap, or since the last time you pressed this button for subsequent laps. Press the play button to go back to the normal timer display. Pressing fast forward or rewind will add or subtract one minute from the displayed time. Hold down the on/off button for a second or so to abort timer mode and go back to the normal clock display. If you want to count up to a specific time, press one of the numeric buttons or up/down immediately after pressing channel+ (within a few seconds). Enter the time to count up to (in a similar manner to setting the time), with a maximum of 23 hours, 59 minutes and 59 seconds. Once you’ve entered the time, press select to start counting. In this mode, the fast forward and rewind buttons change the target time by one minute; it will be briefly displayed when they are pressed, then it will go back to showing the timer. Also, when counting up to a target time, the last decimal point on the display indicates whether the buzzer will sound when the target is reached (by default, it’s on). Press the record (alarm on/off) button on the remote to toggle it while in this mode. Press the channel- (CNTDN) button to initiate counting down. The procedure is essentially identical to counting up, except that you are always prompted to set the initial time, using the same method as described above. Essentially, this mode is identical to counting up towards a target time, except for the fact that the timer starts at the set time instead and counts down to zero. Changing options There are a number of options which can be changed through the “OPTS” menu. Once an option is displayed, use the OK button to change it. Numeric values can be changed using the up/down/left/right buttons or, in some cases, the numeric keypad on siliconchip.com.au the remote. The options are: (1) 12/24 hour time: the display shows either “12 HRS” or “24 HRS”. The hours are shown as 01-12 in 12-hour mode or 00-23 in 24-hour mode. (2) Leading zero blanking: the display shows either “LZB ON” or “LZBOFF”. Press select to toggle between them. Applies only to the first digit on the display, ie, 3pm will be shown as “3:00:00” with leading zero blanking enabled or “03:00:00” with it disabled. This would normally be disabled in 24 hour mode but you can enable it if you wish. (3) Hours/minutes/seconds separator in time display: there are five options: “COLFLA” (colons flash at 1Hz; default), “COL ON” (colons on permanently), “COLOFF” (colons off permanently), “DP ON”, (decimal points on instead of colons) and “DP FLA” (decimal points flash instead). (4) Dimming sub-menu: each entry allows you to set a value between 0% and 100%. “BRIGHT” is the current manually displayed brightness setting. It also changes when the volume+ and volume- buttons are pressed. “ULIM” is the percentage of ambient brightness where the display starts to dim automatically. For example, if set to the default of 75%, the display will be at full brightness between 75% and 100% ambient but will dim below 75% ambient. Set it to 0% to disable auto-dimming. “LLIM” is the percentage of ambient brightness where the display reaches minimum brightness. It will not dim further as the ambient light level falls below. The default is 10%. “MINBR” is the display brightness achieved at the lower ambient limit. Setting this to zero means the display will turn off entirely at the lower amsiliconchip.com.au bient limit. The default is 25%. (5) Piezo buzzer sub-menu: this determines the sound the piezo makes when the alarm goes off or the timer expires. The duration setting is from 0-900 seconds (0 seconds = off, default = 10s). Hz indicates the frequency of the pulses from the piezo between 1 and 10Hz (default = 2Hz). Duty is the duty cycle from 1-100% (default = 50%). Each of these can be set by pressing select, then either up/down or using the numeric buttons to enter a value. Cadence lets you enter three pairs of duration/pause values as a 6-digit number. The default is 100000 which gives an even series of pulses from the piezo at the selected frequency but, for example, a setting of 113200, in combination with a 2Hz frequency, would give a 0.5s beep, followed by a 0.5s pause, followed by a 1.5s beep, followed by a 1s pause, with this pattern repeating. (6) Date format: this defaults to “DDMYY” as is used in Australia. The other options are “MDDYY” or “YYMDD”; affects both date display and setting. Changing infrared codes The infrared menu, labelled “IR” has two sub-menu options: “DISP” and “CHANGE”. If “DISP” is selected, the unit shows the Philips RC5 or NEC code for any button pressed on the remote. Press either pushbutton on the clock itself to exit this mode. If “CHANGE” is selected, you can then select any of the remote button functions (as shown in Fig.8) using up and down and re-program it by pressing OK. The procedure is similar to that described in the initial set-up above. Use the left pushbutton on the clock to abort and leave that code as it is or the right pushbutton to de-assign the existing infrared code for that button and disable it (until a new code is set). Time zone/daylight saving data As mentioned last month, the clock incorporates geographic data, time zone data and daylight savings data which allows it to determine the correct local time virtually anywhere on Earth’s land mass with just the output of a GPS module. The geographic data is shown in Fig.10, plotted on top of the Earth’s surface. Each coloured region represents a different time zone. You may notice that many of the boundaries seem rather sloppy; this is done on purpose as borders defined Last Minute Extras (1) To calibrate the 32kHz crystal, set the XTAL menu option to between -512 (260ppm slower than default) and +511 (260ppm faster). This is adjusted automatically when a GPS module with a 1pps output is used. (2) The unit can show the day of the week. Simply activate the date display function, then press the same button again. (3) A new menu item, “GPSLCK”, has been added to the options menu. If set to “IGNORE”, the unit will use GPS time even if the satellite fix is not perfect. This will allow the unit to work in marginal signal areas although time accuracy may not be quite as good. (4) A new brightness menu item, “CUR RD”, shows the minimum/current/maximum raw LDR readings in 8-bit hexadecimal notation. The fourth digit decimal point lights when the data is going to be saved to flash memory and goes out once it’s saved. This can be used to troubleshoot the autodim function. with fewer points take up less flash memory. Basically, where two time zones meet (eg, at the border of two countries), we accurately define one border, which is often defined by a river or mountain range and thus has many wiggles – often requiring thousands of co-ordinates to define. When we check whether your current location is within that time zone with the well-defined border, and the result is a negative, we don’t need the border for the adjoining zone to be defined with such precision since we already know that if you are near the border, you are on the other side of it, by a process of exclusion. As you can see, the data involved is substantial and it takes up about 150KB, even after a specially designed compression algorithm has been applied. If you’re interested in more details, see the panel on pages 34 and 35 of the Feburary 2015 issue of SILICON CHIP. Time zone data updates We’ve made a substantial effort to provide up-to-date time zone geographical data and daylight savings rules in the firmware for the clock. However, the rules are very complex and vary drastically between different locations. They also change over time, January 2016  43 Table 1: Time Zones & DST Rules Display Details Offset DST Rules AU EAS AU QLD AU SA AU NT AU WA AU EUC AU LHI AU COC AUMAC NZ NZ NZ CHA INTHAI JAPKOR FIJI USA HI USA AK NA WE NA MO ARIZON NA CEN NA EAS ASAMO SA BOL CAN NL CAN NB PERU CAN SK EUWES EU IS EU UK EU EAS EUMOS AS NKO AS BAN AS NEP RUWES AFMOR AF ALG AF LIB AF EGY AFNAM AF AZO AFMAU IRAN AFGHAN ISRAEL GAZA S JORLEB SA SEB SA NEB SA PAR BRAZIL SA URA SA VEN MEXBJC MEX W MEX YU MEX EA RU EAS GEORGI INDIAS MONGO GRQAAN GREENL ATLSSI PA BAK PASAM PA TON PA KIR FR PON PAMAR PAGAM PAPITC NSW, Vic, Tas Queensland, PNG South Australia Northern Territory Western Australia Eucla Lord Howe Island Cocos Islands Macquarie Island New Zealand Chatham Island Indonesia/Thailand Japan/Korea/Palau Fiji Hawaii Alaska USA/Canada West USA Mountain Arizona USA Central USA Eastern American Samoa Bolivia, Eastern Quebec Newfoundland New Brunswick Peru, Ecuador, etc Saskatchewan Western Europe Iceland United Kingdom Eastern Europe Moscow North Korea Bangladesh Nepal Western Russia Morocco Algeria, Tunisia Libya Egypt Namibia Azores Mauritius Iran Afghanistan Israel Gaza Strip/West Bank Jordan, Lebanon South-east Brazil North-east Brazil Paraguay Rest of Brazil Uruguay Venezuela Baja California Western Mexico Yucatan Eastern Mexico Eastern Russia Georgia, Armenia India, Sri Lanka Mongolia Qaanaaq, Greenland Greenland S. Sandwich Islands Baker Island Samoa Tonga, Tokelau Kiribati, Line Islands French Polynesia Marquesas Islands Gambier Islands Pitcairn Islands +1000 +1000 +0930 +0930 +0800 +0845 +1030 +0630 +1100 +1200 +1245 +0700 +0900 +1200 -1000 -0900 -0800 -0700 -0700 -0600 -0500 -1100 -0400 -0330 -0400 -0500 -0600 +0100 +0000 +0000 +0200 +0300 +0830 +0600 +0545 +0500 +0000 +0100 +0200 +0200 +0100 -0100 +0400 +0330 +0430 +0200 +0200 +0200 -0300 -0300 -0400 -0400 -0300 -0430 -0800 -0700 -0500 -0600 +1200 +0400 +0530 +0800 -0400 -0300 -0200 -1200 +1300 +1300 +1400 -1000 -0930 -0900 -0800 AUST AUST AUST AUST (+30) NZ NZ FIJI NTHAM NTHAM NTHAM NTHAM NTHAM NTHAM NTHAM NTHAM EURO EURO EURO MOROC EGYPT NAMIB EURO IRAN ISRAEL PALEST MIDEA BRAZIL PARAGU BRAZIL URUGUA MEXIC MEXIC MEXIC MEXIC EURO MONGO MEXIC GRNLND SAMOA - 44  Silicon Chip so we decided there needed to be a way to keep the rules up-todate, at least for the locations that constructors occupy. As a result, the clock has the facility for you to change the rules for your current location. Updates are stored in the same section of flash memory as the clock options are kept and override the built-in rules. There are three basic parameters for each location that can be changed: offset from UTC (in hours and minutes), daylight savings time shift (+0, +30 or +60 minutes) and daylight savings rules. The menus that provide these options also offer some information regarding the currently detected time zone and GPS module status. There are 19 different sets of daylight savings rules, listed in Table 1 under “DST Rules”. Table 1 also shows which set of rules is used by default in each location. The time zone menu allows you to change the setting for your current location to one of the other rules, including disabling daylight saving for a zone which previously used it, or enabling it for one which did not. To change these options for your location, go into the “CHA TZ” menu (which appears when the unit has a GPS fix). The first five menu items simply show information; press OK to display that particular parameter and then escape (on/off) to go back to the menu. Of the remaining three, “OFFSET” allows you to change the difference in hours and minutes between UTC/GMT and your time zone. This can be set anywhere from 22 hours before UTC to 22 hours after UTC in 15 minute intervals, although few locations use offsets of more than 12 hours from UTC. “DAYDEL” allows you to select how much the time changes when daylight saving starts and ends. This will almost always be one hour (60 minutes) although there is one location, Lord Howe Island, which has a half hour (30 minute) DST delta. To disable daylight saving in your location, you can either set this to zero or change the DST rule to “NONE”. “DAYRUL” allows you to select the DST rules for your location. These rules define which hour of which day DST starts and ends in a given year. Changing DST rules Since these rules can also change, there is a separate menu called “CHADST” to change them. There are nine DST settings for each rule, represented by nine menu items, of which four define when it starts and four when it ends. The ninth determines how these are interpreted. The most common mode, used by the vast majority of locations, is “HDWM” which stands for “hour, day, week of month”. For example, in Australia at the time of writing, daylight saving starts at 2am on the first Sunday of October and ends at 2am (3am DST) on the first Sunday of April. So in this case, the mode is HWDM and the following rules are used: STAMO: 10 OCT STAWE: 1ST STADAY: SUN STAHR: 2 FINMO: 04 APR FINWE: 1ST FINDAY: SUN FINHR: 2 (In this menu, the hour values always refer to the time before daylight saving is applied, hence FINHR is 2, not 3). The following countries use different modes. Iran uses “EQUINO” where DST start/end dates are relative to the spring and autumn equinoxes. Brazil uses “NOCARN” which is identical to HDWM except that DST changes are delayed by one week if they fall during Carnaval. Similarly, “NORAM” delays DST changes if they fall during Ramadan and “NOROSH” delays DST changes if SC they fall during Rosh Hashana. siliconchip.com.au