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BY MAURO GRASSI Review . . . Altium Designer & the NanoBoard 3000 Altium Designer is software for designing PC boards, circuit diagrams, Field Programmable Gate Array (FPGA) projects and embedded software. It can work with the NanoBoard 3000 hardware platform and its supplied software libraries let you quickly develop, test and debug a device without the need for any hardware design or manufacturing. A RGUABLY THE premier design package in Australia, Altium Designer has so many features that it’s impossible to cover them all in this review. Basically, it is a comprehensive electronics design package encompassing a PC board layout and circuit diagram editor, a Computer Aided Manufacture (CAM) manager, and an FPGA and embedded software Integrated Development Environment (IDE). Also included are simulation tools, version control, test instruments, software libraries and more. This review refers to the features of the Summer 09 edition. We will 90  Silicon Chip cover the most important aspects of the software but will necessarily leave out others due to space constraints. If you require further information on these, take a look at Altium’s online resources at www.altium.com Migrating from other software Many readers will be familiar with the existing Electronic Computer Aided Design (ECAD) packages such as Autotrax, Easytrax, Protel 2.8, Protel 99SE, EAGLE and KiCad. Other packages include Allegro and OrCAD from Cadence and PADS from Mentor Graphics. Altium Designer is an all-in-one package which can do what they can and more. Its import wizards allow existing Autotrax, Protel, Allegro, OrCAD and PADS files to be used. As Altium was formerly known as Protel, it’s not surprising that Altium Designer retains some of the elements of Protel 99SE while adding new features and improving on old ones. If you’ve used Protel 99SE, migrating to Altium Designer will be relatively straightforward. 3D PC board editing One of the great features of Altium siliconchip.com.au Above: the NanoBoard 3000XN is a comprehensive hardware development platform based around a powerful FPGA. It’s programmed via a USB cable from inside Altium Designer. Designer is its 3D visualisation package. This allows you to see what a PC board will look like in three dimensions while editing it without having to build it. The 3D rendering is fast enough to allow interactive use and you can even see the layers inside the PC board. The 3D capabilities of Altium Designer are best explored with a Space­ Navigator™, a joystick-like device from a company called 3DConnexion (www.3dconnexion.com). It enables you to change the viewing position and zoom distance in an intuitive way. Altium Designer supports such devices out of the box but you can also use a mouse if necessary. While Protel 99SE could produce a 3D view of a PC board, Altium Designer has a much better engine that allows some basic board editing in 3D mode. For example, components can be moved or deleted and properties can be changed. The 3D view can be used to check that the PC board fits inside its enclosure, for example. This is done by superimposing a transparent 3D model of the enclosure on the board. It is also useful for checking for electrical errors in the layout of the PC board and for checking that parts don’t physically interfere with each other. Copper tracks, vias and pads are rendered siliconchip.com.au realistically, as well as any silk screen layers. This makes it easy to spot common errors, such as overlaying the silk screen on a pad or via. While some of the components in the supplied libraries already have 3D bodies, you can also easily create a default component body by selecting which outlines to extrude. This will be sufficient in most cases but you can also add realism by using texture mapping, where an image can be attached to a component’s surface. However, texture maps cannot be wrapped around a cylinder, eg, for an electrolytic capacitor. Components without a 3D representation are simply shown as pads and silkscreen outlines. Interactive routing Arguably the most important part of a PC board layout tool is the track routing support and in this respect Altium Designer is exceptional. Its interactive routing modes include “Push and Hug” routing, “Walkaround” (track hugging) and “Track Slicing”. “Push and Hug” mode allows you to literally “push” a number of tracks to make room for new ones, without having to delete and re-route them. By contrast, “Walkaround” allows you to easily route a track so that it’s adjacent to existing tracks, to most efficiently use the available board area, especially when routing busses. Finally, “Track Slicing” allows you to break tracks along a line defined by the mouse. All these features are great aids in the sometimes painstaking work of routing PC boards. Push and Hug is also handy when it comes to moving tracks. If there are several parallel tracks and you try to move the one at the edge inwards, they are all automatically moved so that they remain parallel with the appropriate clearance. Doing this in other ECAD packages can require a lot of manual editing. There are other time-saving features. Tracks and pads are automatically labelled with the net name or pin designator if they are large enough. When the mouse is moved over a track, its entire net is highlighted, giving a clear indication of what it is connected to (a “net” refers to all the points in a circuit that are electrically joined). One problem that many ECAD packages have is that tracks can become fragmented as they are edited. You can often end up with a track composed of separate smaller segments, which is undesirable. Altium Designer takes a good approach – a background process is always running that automatically detects co-linear track fragments belonging to the same net and converts them to a single segment. There are some rare cases where this process does not correctly merge segments, eg, if two segments are not perfectly aligned, so that they do not share a vertex. This can happen when changing the measuring unit for the grid from Imperial to metric or vice versa, where rounding off errors can be introduced. Differential pair routing For both radio frequency (RF) and high-speed digital signalling, good layout techniques are critical. A “differential pair” is a pair of tracks on a PC board which carry signals which are opposite in polarity. The same technique is used in twisted-pair cables as it reduces crosstalk and electromagnetic interference (EMI). Proper differential routing is especially important in high-speed signalling applications such as Hi-Speed USB (Universal Serial Bus) 2.0. The USB D+ and D- lines are a differential pair, a requirement for achieving the maximum transfer rate of 480Mbps. November 2010  91 Fig.1: a 2D representation of a PC board in the layout editor. The blue tracks are on the bottom layer and the red tracks are on the top layer (representing wire links). You can also see the rats’ nest connections corresponding to the nets in the circuit diagram. Note that, in practice, the colours are much more vivid on-screen than shown here. This type of routing is becoming increasingly common with the growing use of faster serial busses like eSATA and USB 3.0. Altium Designer allows you to tune the length and impedance of tracks as you route them. This is useful for impedance matching (which reduces signal reflections and therefore waveform distortion) and laying microstrips (a form of waveguide made from PC board tracks). These are especially important for wireless devices which can operate at 2.4GHz or more. Multi-channel design When designing a PC board, sometimes identical sub-circuits need to be laid out. For example, in a stereo audio design, the two channels may require duplicate circuits. A common solution is to lay out one channel and then duplicate it. However, this technique is less than ideal because when changes have to be made they must be made to all the copies. Altium Designer takes a better approach to this with its “multi channel” design feature. You only maintain a single copy of the sub-circuit, which is then linked to multiple parts of the 92  Silicon Chip PC board or circuit diagram. When you change the master copy, all the other copies change too. Layer stack A PC board often consists of multiple layers although two layers is the most common (ie, a double-sided PC board). Different layers are shown in different colours, with blue often used to represent the “bottom” layer and red the “top” layer. In order to connect a bottom layer track to a top layer track, a “via” is used. This is usually a small pad on each side of the board, with a copperplated through hole connecting the two layers. Vias are used for boards with more than two layers as well but in this case, they do not necessarily connect all the layers of the board. Some may not be visible on the surface of the PC board which is formed from a “sandwich” of substrates. The top and bottom layers are called “external” layers, while the rest are called “internal” layers. While the 2D representation of the PC board can show the internal layers by using additional colours, as the layer count increases it becomes more difficult to see which layers a via is connected to, especially if it is a “blind” or “buried” via. A via which passes through one external layer but not the other is called a “blind via”, while a via which is only between internal layers (and thus not externally visible) is called a “buried via”. Keeping track of which vias (or multi-layer pads) connect to which tracks is made easier by using the “Layer Stack” feature. This shows a cross section of the PC board around the selected via and shows which layers it connects to (see Fig.5). Pin swapping The PC board layout tool also allows you to perform “pin swapping”. This is especially useful for designs using high pin count FPGAs or micro­ controllers. It allows you to swap the nets (ie, all the connection points) associated with two pins. If an IC’s pins can be re-mapped, it’s possible to greatly simplify the layout of the PC board by carefully selecting which pins connect where. This minimises track crossings (resulting in a much simpler layout), keeps tracks short and makes differential routing siliconchip.com.au Fig.2: a 3D view of the same PC board as in Fig.1. Realism has been added by defining leads for most of the components and texture maps for the relays and capacitors. The orange cone is the 3D cursor. easier. Quite a few pins may need to have their functions swapped before the ideal layout is achieved, so automating this process is very helpful. Linking to online databases An important part of hardware design is selecting and sourcing components and the trend is to do this online. Altium Designer allows you to access suppliers’ databases directly and large suppliers such as Farnell, Newark and Digikey currently offer access to their inventory via this software. Not only can you search their online databases and access technical information about the component (including the data sheet) from within Altium Designer but you can also check stock levels and place an order. More importantly, with some of the newer components, you have access to component footprint information and STEP models (Standard for the Exchange of Product model data). This allows you to insert the component directly into your design from the vendor without having to go though the time-consuming (and error-prone) process of manually creating component symbols and footprints. STEP is a standard way of describsiliconchip.com.au ing the mechanical specifications of a component. It can be used to give assembly details too, including any dependency relationships between components. For example, a component may need to be installed before another one, meaning the order of assembly may be crucial. Altium Designer can also use these STEP models to render a 3D model of the component (for 3D visualisation of the PC board) and to improve its “Design Rule Checking”. Design Rule Checking Design Rule Checking (DRC) is a way of verifying a PC board against a list of rules or “constraints”. For example, you can check whether tracks or pads are too close together, or whether tracks that shouldn’t be joined do in fact join. You can also check whether pins on a component have been left unconnected or if one component’s body interferes with another. Altium Designer’s DRC is comprehensive and easy to customise. You can even check the integrity of a signal using its circuit simulator and any violations of the rules are summarised in a report file. Clicking on an error in the report takes you to the relevant place on the PC board, which is highlighted. This list is also made available in a floating window, so that the violations can easily be checked in turn. In addition, Altium Designer supports “Live DRC”, with the board being checked against the design rules as you work on it. This is very handy as, for example, you can determine how wide a track can be to fit between components without violating clearance constraints and so on. Components which violate constraints are highlighted with a special pattern and annotated, thereby streamlining the design process. Linking circuits & PC boards Usually, a circuit diagram is drawn before PC board layout begins. To draw a circuit, Altium Designer’s Graphical User Interface (GUI) allows components to be placed on a “sheet”, labelled and connected via wires to form the nets. Each component has both a symbol and one or more footprints associated with it. The symbol is used in the circuit diagram while one of the footprints is selected to go on the PC board. Basically, the symbol represents the component’s electrical properNovember 2010  93 Fig.3: another 3D view, this time from the side. Unplaced components are visible in the background along with their rats’ nest connections. The height of components is more obvious in this view. ties while the footprint also contains mechanical information, such as the physical size of the component and its pad locations. For a transistor, the symbol would be the typical transistor diagram showing the base, emitter and collector. The footprint, on the other hand, would typically consist of three pads and a silk screen outline of the body. It might also include additional information to render a more detailed 3D body, as shown in our screen grabs. Once the circuit diagram is complete and has been successfully “compiled” (which involves creating a complete global netlist), you can “synchronise” the schematic to the PC board. This results in the appropriate footprints being placed adjacent to the board so that they can be moved onto it. You can see some of these unplaced components in Fig.3. It is then possible to use either an automatic placement algorithm (which obeys the design rules) or manually place the components yourself. Lines are drawn between pads which need to be connected (the so-called “rats’ nest”) which can help determine the best location and orientation for each component. 94  Silicon Chip If the circuit is later changed, those changes can be re-synchronised to the PC board and vice versa. Circuit simulation Altium Designer has integrated support for simulation environments, including ModelSim and various flavours of SPICE (Simulation Program with Integrated Circuit Emphasis). These numerical simulations, together with Altium Designer’s virtual instruments and its support for test points, allow a design to be partly tested before it is built. Manufacturing outputs When the PC board is ready for manufacture, you can use the Computer Aided Manufacture (CAM) manager to export Gerber plot files, NC drill files and data in newer formats like ODB++ (a proprietary format that is increasing in popularity). These can then be sent to a PC board manufacturer. The CAM manager is quite powerful. You can import Gerber files, “panelise” your design (ie, put multiple boards into one file) and create SMT (Surface Mount Technology) solder stencils for reflowing. You can also generate product assembly informa- tion, including files to control pick and place machines for assembly. Altium Designer also makes it easy to generate a BOM (Bill Of Materials) for parts ordering. It can also produce schematic and PC board hard copies, manufacturing data, mechanical drawings and so on. You simply select what kind of data to produce and Altium Designer will generate the files with a single click of the mouse. NanoBoard 3000 The NanoBoard 3000 is a hardware development platform that’s integrated with Altium Designer. It is ideal for rapid prototyping but can also be used for production, especially where small runs are involved. This can be economical as the extra cost of the hardware can be offset by greatly reduced development time. In addition, Altium can supply modular and stackable plastic enclosures for the NanoBoard. The NanoBoard 3000 contains an impressive amount of hardware, the core being a powerful FPGA. In fact, there are actually two FPGAs on the NanoBoard 3000, with one used to program the other and to control the peripheral functions. siliconchip.com.au As well as generous amounts of DRAM, SRAM and FLASH memory, the NanoBoard 3000 also has the following peripherals: (1) a battery-backed Real Time Clock (RTC); (2) a 3-port USB host controller; (3) a USB 2.0 Hi-Speed device port; (4) an ethernet controller and port; (5) an SVGA port; (6) MIDI input and output ports; (7) RS485 and RS232 serial ports; (8) an analog audio output, input and headphone connector; (9) PS/2 ports for keyboard and mouse; (10) S/PDIF digital audio input and output ports; (11) a TFT QVGA (320 x 240) LCD touchscreen; (12) stereo speakers; (13) four relay outputs; (14) two memory card sockets; (15) analog-to-digital converters (ADCs) and digital-to-analog converters (DACs); (16) RGB LEDs and an IR receiver. In addition, there’s a prototyping area on the board and external connections can easily be made using the terminal blocks. It’s also possible to connect “daughter boards” for WiFi, GSM modem or bluetooth support and a USB 2.0 WiFi adapter can also be used. PC board layouts and circuit diag­ rams for the NanoBoard and the daughter boards are provided with Altium Designer, so you can even design your own daughter boards. The board is supplied with a USB cable, a switchmode plugpack, a generic infrared remote control and a stylus for use with the touchscreen. Note that there are different NanoBoards available, depending on which FPGA you prefer. The model we tested was the NanoBoard 3000XN, equipped with a 676-pin Xilinx Spartan 3 FPGA in a small Ball Grid Array (BGA) package. The Spartan 3 has an equivalent gate count of 1.4 million and this is enough to implement a 32-bit CPU (known as a “soft core”) with room left over for peripherals. Once the soft core is loaded onto the FPGA, you can write firmware for it just like you would a regular microprocessor, with the added benefit of customisable peripherals. FPGA configuration The NanoBoard 3000 plugs into siliconchip.com.au Fig.4: a screen grab of the online database access window. In this case, we are accessing the online database of Digikey, looking at a Microchip microcontroller. your PC using the supplied USB cable and is configured via Altium Designer. This includes configuring the FPGA and loading software into it for any soft cores being used. Altium Designer has a GUI for FPGA design. You can draw a diagram consisting of logic blocks, inverters, gates, flipflops, shift registers and so on, all the way up to soft cores and peripherals. The “synthesis software” then configures the FPGA to implement your design. It’s a great teaching and development tool, as very little knowledge of the low-level details is necessary to design a working project. For more complex designs, Verilog or VHDL can be used to describe the desired hardware. Each FPGA vendor provides free synthesis tools for their range of FPGAs. This must be installed so that Altium Designer can work with it. The FPGA component libraries included with Altium Designer have Wishbone-compliant interfaces. This means that they are compatible with many of the OpenCores designs. Wishbone is an open source bus for connecting hardware blocks. OpenCores is a project that aims to provide open source hardware components in the form of verified HDL (Hardware Description Language) code. For more information on this, go to http://opencores.org/ Adhering to this standard allows freely available code to be imported into your next design, thus saving development time. Embedded software IDE Altium Designer supports embedded software development by including C and C++ compilers, as well as various assemblers. If you are using one of the royaltyfree IP soft cores, the software libraries include a lot of the low-level driver software for the hardware interfaces. This includes a TCP/IP stack, USB pro- Fig.5: the “Layer Stack” shows a crosssection of a via or pad. It can be used to see what layers the via connects to, a feature that’s especially important for PC boards with more than two layers. November 2010  95 What Is A Field Programmable Gate Array? An FPGA (Field Programmable Gate Array) is a digital IC that is software configured using a Hardware Description Language (HDL). You can think of it as a custom digital logic IC that can be configured to suit your application. While both FPGAs and microprocessors can be reconfigured to suit the task at hand (in the latter case, via software), the ability to change an FPGA’s hardware configuration means that it can usually deliver much greater performance for the same clock speed and power consumption. This is possible because an FPGA consists of many “logic blocks” which are connected via multiplexed lines (or “multiplexes”). There are many general-purpose logic blocks for performing arbitrary operations, as well as specialised units to perform common tasks such as data storage, multiplication, shifting, etc. The multiplexes are configured by memory (usually SRAM, EEPROM or Flash) and this determines how the logic blocks are interconnected, so by writing to this memory, the circuitry is reconfigured. It is a bit like a giant high-speed breadboard with programmable wire links. Virtually any digital circuit can be implemented on an FPGA, as long as it has enough logic blocks. The “equivalent gate count” statistic is an estimate of how the FPGA compares to an Application-Specific Integrated Circuit (ASIC, ie, custom IC). If an FPGA is quoted as having one million equivalent gates, then it can take on the function of a typical ASIC with one million gates or less. This statistic is especially useful for comparing FPGAs across different manufacturers since the internal structure can be different and therefore comparing the number of logic blocks is not valid. The best FPGA performance is achieved by making full use of its specialised logic blocks while keeping the interconnections as short as possible. Fortunately, you don’t have to worry about that, as the synthesis software provided by the FPGA manufacturer works it out for you automatically. A hardware synthesis tool is a program which takes a circuit description and determines the best way to implement it using the available hardware building blocks. Typically, the input to a synthesis tool is a Hardware Description Language (HDL) such as Verilog or VHDL. However, with Altium Designer, you can draw an equivalent circuit diagram and the software will generate the HDL for you. Note that hardware synthesis tools are also available for ASIC design so hardware which is prototyped in an FPGA can later be built into a custom IC which will be smaller and faster. While custom ICs are cheaper in large quantities, the set-up costs are huge, so FPGAs are often used for small production runs. tocol handlers, MIDI and audio codecs, image processing libraries and much more. In short, the software support is truly comprehensive. Version control In any project large enough to require multiple designers, version control is critical. Version control systems allow many people to work on a large set of files without “stepping on each others’ toes”. It also helps track down bugs by storing a history of changes for each file and assists with upgrades and testing by keeping track of multiple file and project revisions. Altium Designer integrates with open source version control systems like CVS and Subversion. These are also useful for creating automatic back-ups, while the ability to revert to an earlier, stable version lets you add features with minimal risk. Comparison engines allow you to track 96  Silicon Chip and merge changes between different file versions. C-to-hardware compilation A unique feature of Altium Designer is its ability to automatically build hardware acceleration support for C functions. The compiler can automatically implement hardware in the soft core to accelerate performance-critical functions within the software. This is possible because both the hardware and software can be reconfigured to suit each other. This technique can yield substantial gains in performance, especially for computationally-intensive routines. While there are some limitations as to what kind of functions can be exported to hardware, it is a powerful feature. Online resources Altium Designer gives you access to a wealth of online resources. It includes an integrated web browser which you can use to access the Altium Wiki, the “Resource Center” (with videos and tutorials) and an online community with forums. There is also a Support CENTER, accessible with a valid licence, for better technical support. Tutorials are freely available online and some training will be needed to use the software effectively. Training sessions are hosted by Altium on a regular basis. Conclusion Altium Designer is not simply a suite of tools and substantial effort has been put into integrating all the components. There are powerful cross-probing features, where you can select an item on the circuit diagram and have it selected on the PC board as well. Overall, it is a comprehensive and well-presented package. There are various licencing options for Altium Designer. The standard perpetual licence costs $A6240 + GST but you would also usually purchase a 12-month software assurance for an extra $A1995 (exc. GST), giving access to the biannual updates. This software assurance can (optionally) be renewed annually. For students, Altium offers complete versions of Altium Designer on 12-month licenses for $A115 + GST. The NanoBoard 3000XN costs $A495 (exc. GST) and includes a “soft design licence” for 12 months, allowing you to use the FPGA tools in Altium Designer for development. This licence expires after a year unless you renew it for another year for $A295 (exc. GST). While Altium Designer is not cheap, it offers good value for the amount of software provided. It is a complete solution for almost all general electronic design and also includes access to online resources and support. Although the software has been optimised for performance, you will need a reasonably up-to-date system to use it effectively. Altium’s website lists the minimum requirements. Contact details For further information on Altium Designer or the NanoBoard 3000, contact Altium. Their website at www. altium.com contains a lot of information about their products, including SC information on new features. siliconchip.com.au