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PICAXE VSM: Getting It Going! In this second part of our mini-series, Clive Seager talks us through using the new PICAXE VSM simulation software. L ast month we introduced the new PICAXE VSM software, which will allow you to simulate PICAXE designs on the computer to see if they (or your software!) will do what you intended to do! As well as a serious design tool, PICAXE VSM is also a great way for beginners to experiment with PICAXEs – without any risk of letting the smoke out! What’s more, PICAXE VSM will help you with the circuit so that you can actually build your PICAXE project. Installation To install the PICAXE VSM software download the demo installation package (18MB) from www.picaxevsm.com If you are on dial-up and prefer a CD your local PICAXE distributor should be able to oblige. The software is designed for Windows 2000, XP, and Vista. 95, 98 and ME are not officially supported, however many users have reported that the software does actually run on these older Windows versions. The software will run in restricted ‘demo’mode until you purchase a licence key (you can still use the Rudolph simulation sample described below in demo mode). Registration is also carried out online, again at www. picaxevsm.com, via secure credit card transaction, you Overview Window Object Selector Design Area Animation Control Panel 78  Silicon Chip siliconchip.com.au Fig.1: you not only get the simulation, you can also see the program stepping through line-byline AND see the variables in another window. will receive an email with your key shortly after purchase (VSM costs UK ₤49.99 (~AU$118 at press time). Use the PICAXE VSM ‘Licence Manager’ utility to install your key and ‘unlock’ the full version. Let’s Begin! PICAXE VSM is a powerful piece of software and so will naturally take a little while to learn. To get started the most important thing is to be sitting comfortably with one hand on the mouse and the other on the keyboard! As with most graphics packages, the software uses keyboard shortcuts as well as the mouse. These take a little while to get used to but you should very quickly learn the shortcuts and appreciate how they speed up use of the software. So to learn basic navigation lets start by opening the existing ‘AXE107 Rudolph.dsn’ example from the / samples/(Demo Version Samples)/PICAXE folder. Then move the mouse over the design and press the <Z> zoom, <U> unzoom and <P> pan keyboard keys as you move the mouse around the design – see how you can zoom in and out very quickly by using keyboard and mouse at the same time! If you are already familiar with a different graphics/ PCB application that uses different shortcut keys, you can easily customise ‘PICAXE VSM’ to your preferred shortcut keys. To do this use the ‘System>Set Keyboard Mapping’ menu. Object Selector While the sample design is open, let’s look at the different parts of the screen. The main editing window is obviously where you draw and edit your designs. To the left of this is the ‘Object Selector’ list, that lists all objects (components) currently used in the design. Above the ‘Object Selector’ is the ‘Overview’ window, which we will look at later. At the top and left of the screen are menu bars, and at the bottom of the screen is the ‘animation control panel’. This looks like the buttons on a traditional tape recorder (remember the days before CDs and MP3s?) – Play, Forward, Pause and Stop. Simulation Click on the ‘Play’ button at the bottom left of the screen and the Rudolph simulation will compile and start. When you click on the animated pushbutton switch, a tune will siliconchip.com.au play on the piezo sounder (simulated via the computer’s speaker) and the LEDs will flash. The actual tune played will be decided by the resistance of the LDR – varying light levels are simulated via the up and down buttons beside the LDR (you may wish to zoom in using the <Z> key). While the simulation is playing click the pause button at the bottom of the screen. This will pause the simulation and open up a number of other ‘debug’ windows, which show, for instance, the variable values and the PICAXE program. (Tip - you can select which PICAXE windows are automatically displayed by checking them in the ‘Debug’ menu while the program is paused). If so desired you can now also step through the PICAXE program line by line, by clicking on the ‘Step into Source’ button on the Program window. You can also run at full speed again by selecting the ‘Run’ button. While the Program window is open, practice setting ‘break points’ by clicking at the left hand side of any program line – a red circle will appear. This means the program will run until this particular point and then stop – ideal for debugging those problem programs. Try it out! One final tip for simulation, if you want to step through a program line-by-line right from the start, simply click ‘pause’ (rather than ‘play’) to start the simulation. This will start the simulation and automatically break on the first program line. Our first circuit! Now click File>New Design menu and select the default template layout (this gives you a blank A4 paper size layout). It is good practice to give your design a title, so use the ‘Design>Edit Design Properties’ menu to enter a title, version number and your name. Also save the file now, and remember to keep saving every so often as you work through creating your masterpiece! Now we need to build the design. To start with we will February 2008  79 Fig.3: this is the list of components you will require for the Rudolph project. Fig.2: use the ‘Design>Edit Design Properties’ menu to enter a title, revision number and your name. Also save the file now and remember to keep saving every so often as you work through creating your masterpiece! just create a straight copy of the existing Rudolph design from scratch – you may find it useful to print it out to copy. The first thing is to add parts to our ‘Object Selector’. To do this click on the small ‘P’ at the top of the ‘Object Selector’ (which is a shortcut for the ‘Library>Pick Device’ menu). We now have a list of 10,000+ components to search through. This could be daunting but fortunately a very powerful search facility and special ‘PICAXE’ category enables us to quickly locate the parts you want! Start by typing in ‘LED’, and then click on the ‘PICAXE’ category. You will then have a much smaller list to choose from! Double click on LED-RED and LED-GREEN. This will add then to the Object Selector. Delete the ‘LED’ text and change to ‘resistor’, then click on the PICAXE category again. Double click on the 330W, 10kW and 22kW resistors. Fig.4: there are two ways to display the PICAXE chip -– the choice is yours (depending on which one you’re used to). Then repeat this process for all the parts in Fig.3. Note there are two options for the PICAXE chip, either ‘traditional’ schematic format (which has the power pins hidden) or ‘IC’ layout. Choose whichever you prefer, then close the ‘Pick Devices’ window. Let’s draw! First job is to drop the parts onto the screen, copying the Rudolph design layout already used. Leave plenty of space between components to start with, you can always ‘tidy up’ later. To select the first part to drop, click on it in the ‘Object Selector’. A preview of the item will be shown in the ‘Overview’ window. Then move over the design and click to drop it in place. You can then drop another of the same component straight away, or select a different component from the Object Selector. When all the components are placed click on the ‘Selection Mode’ arrow (top of the left hand toolbar) to move out of ‘Component Mode’ If required components can be rotated and mirrored to make a neater schematic. To do this right click over the component and select the appropriate menu option. Fig.5: a very powerful search facility and special ‘PICAXE’ category enables us to quickly locate the wanted parts! 80  Silicon Chip siliconchip.com.au Your components names (R1, R2, R3 etc) should automatically be added as the components are dropped. If you just get ‘R?’ instead of a number make sure that ‘Tools>Real Time Annotation’ menu is enabled. If necessary ‘R?’ can be changed to a number simply by double clicking the label and editing. You will also need to add a couple of ‘Ground’ and ‘Power’ terminals. To do this right click the mouse and select P l a c e > Te r m i n a l > Ground and then P l a c e > Te r m i n a l > Power. The default powFig.6: components can be rotated er rail is always and mirrored to make a neater 5V, if you want to schematic. To do this, right-click change this (e.g. to over the component and select the appropriate popup menu option. 4.5V to simulate 3xAA cells) use the ‘Design>Configure Power Rails’ menu. Wiring Finally we need to wire the components together. Make sure no part is currently selected (a useful tip is just to click on a blank part of the screen to clear any selection) and then move the mouse over a component pin. The mouse cursor will change to the ‘pencil’ shape and you can then click to start the wire. Move the cursor to draw the wire, clicking wherever you want to fix a corner. Finish the wire by clicking over the second component pin (or on to another wire). You cannot draw wires over labels or components, so always leave plenty of room between parts. The wires will automatically move if you later drag a connected component, so it is easy tidy up designs at a later point. To delete a wire simply right click and select delete. Segments of wires can also be individually dragged when the wire is highlighted. Note that you must specifically wire all parts together. Two components pins placed ‘overlapping’ each other will not be ‘electrically’ connected within the design. PICAXE Program Before the simulation can run we need to allocate a PICAXE program to the PICAXE-08M component. This is done via the ‘Source>Add/Remove Source File’ menu but first you have to type in and save the PICAXE BASIC file! This can be carried out using the normal PICAXE Programming Editor software, or the simple ‘Source Editor’ siliconchip.com.au Fig.7: type in this test program and save it as a .bas BASIC file in the same folder as your .dsn design file. Fig.8: make sure the PICAXE chip (eg, U1) is highlighted as the target processor. Then click ‘New’, select your file and then click OK. application provided with PICAXE VSM. Type in the test program shown in Fig.7 and save it as a .bas BASIC file in the same folder as your .dsn design file. I recommend that you always use the same filename stem to avoid confusion. Back within PICAXE VSM select the ‘Source>Add/Remove Source File’ menu and make sure the PICAXE chip (e.g. U1) is highlighted as the target processor. Then click ‘New’, select your file and then click OK. If you now go back to the ‘Source’ menu you will see your program file is now listed within the menu. If you click on the filename it will now open within the ‘Source Editor’. This is a very useful shortcut if you want to tweak and save modifications to your BASIC program while simulating and testing. Run Your First Program. Click ‘Play’ and if all is well your two Rudolph eye LEDs should now start flashing every second! Congratulations, that is your first PICAXE VSM design created and simulated. To have a play with the LDR, switch and piezo have a look at the example BASIC file provided within the ‘AXE107 Rudolph.dsn’ sample design file. We’ve run out of space for this month. Next month we will look at a couple more complex designs and learn how to use some of the virtual instruments – voltmeter, oscilloscope and even an I2C debugger! SC February 2008  81