Ohio Linux Fest. Embedded Development with Linux. Tools for embedded development. John McDonough

Transcription

1 Ohio Linux Fest Tools for embedded development John McDonough Copyright 2012 John J. McDonough. This material may only be distributed subject to the terms and conditions set forth in the Creative Commons Unported Share Alike (CC-BY-SA), V3.0 or later (the latest version is presently available at creativecommons.org/licenses/by-sa/3.0/). Abstract Linux provides a complete suite of tools for embedded development, not only the hard stuff, but also the less hard (but still firm) parts. This paper gives an overview of the tools, both open and not so open source, available for circuit and firmware design. Although the focus will be on the Microchip PIC family, many of the tools are applicable to other devices. The paper is more focused on the hobbyist; ASIC and FPGA design tools will not be covered. 1. Introduction Hardware versus Software Hardware geda qucs xcircuit gnucap kicad rcrpanel Firmware Basic Tools Integrated Development Environments Miscellaneous Tools A. Revision History 21 1

2 1. Introduction Embedded development bears many similarities to ordinary development, but also differences. The target is often very small, with peripherals that are frequently different than those found in larger computers. Memory and speed are typically limited. But perhaps the most striking difference is that, in general, the target hardware doesn't exist before the project is started. The hardware must be designed and constructed before the firmware can be tested. Linux offers a wide range applications for embedded development, from schematic capture and printed circuit board layout tools, to circuit simulators, to assemblers, compilers and debuggers for various targets that frequently participate in embedded designs Hardware versus Software Software developers often distance themselves from hardware developers, but in many embedded projects, the software is tightly tied to the hardware. As a result, the same person or team is often involved in both aspects of the project. This makes sense, because tradeoffs can often be made between hardware and software complexity. In most embedded applications, the "software" is actually embodied in non-volatile memory, typically FLASH but sometimes other technologies such as fusible link ROM, so it isn't "soft" like RAM based code, and is more typically referred to as firmware. The hardware and firmware development phases often have very different characters, so we will separate them in this paper. However, the reader should be aware that "iterative development" can often mean iterating the hardware as well as the firmware. The two are not nearly as separate as some might think. 2. Hardware Any embedded project requires hardware, and more often than not, the hardware must first be developed. The initial stage of hardware development is conceptualizing the overall product. There are many conceptual tools available, but they are not specific to embedded projects and thus will not be covered here. Hardware development typical follows several steps: Schematic Capture 2

3 geda Netlist generation Circuit Modeling Printed circuit board layout Gerber review BOM generation We will review tools for all these steps geda geda, the gnu Electronic Design Assistant is a suite of tools for hardware design. geda encompasses all the necessary steps, and is perhaps the most "industrial strength" set of tools for the purpose. The geda suite consists of a large number of tools. We will review the more obvious members, but there are many others for small tasks that often need to be undertaken. The primary tools are: gschem for schematic capture gnetlist for converting the schematic to a SPICE netlist ngspice for circuit simulation pcb for laying out the printed circuit board and generating the BOM gerbv for reviewing Gerbers In addition, there are a number of tools for various utility functions such as renumbering reference designators, converting symbols and footprints from other formats, etc gschem gschem is the schematic editor in geda. gschem has a wide range of symbols available, and additional symbols are easily added. 3

4 Figure 1. gschem schematic editor gschem schematics may be read by gnetlist to produce netlists for SPICE, pcb, or any of a number of other purposes. The utility gsch2pcb can translate the schematic into a set of files for input to pcb layout. All symbols and schematics are text files, so symbols are easily modified or new symbols created. The utility gsymcheck can validate symbols gnetlist gnetlist is a command line application which creates net lists in a variety of formats. Output formats available are: Allegro netlist format BOM / BOM2 - Bill of Materials DRC - Design rule checker Gossip netlist format PADS netlist format PCB / PCBboard VIPEC netlist format Bartels Autoengineer netlist format GOSSIP system simulation system netlist format MAXASCII netlist format VHDL-AMS netlist format Futurenet2 netlist format SWITCAP switched capacitor simulator netlist format RF Cascade netlist format 4

5 geda RACAL-REDAC netlist format SystemC netlist backend Calay format netlist backend Osmond format netlist backend Eagle netlist format Netlister for symbolic circuit analysis using Mathematica LiquidPCB format netlist backend PCB actions file for forward annotating pin/pad names from schematic to layout gsch2pcb backend ProtelII netlist format Spice compatible netlist format Enhanced spice compatible netlist format Tango netlist format Verilog code VHDL code Figure 2. gnetlist For specialized purposes, gnetlist can accept user-written scheme files to preprocess or postprocess the results ngspice ngspice is the SPICE circuit simulation within geda. Unlike traditional SPICE, ngspice can simulate mixed models containing digital as well as analog elements. ngspice is a command line application which can display results graphically as well as in text format. 5

6 Figure 3. ngspice circuit simulation There is also a GUI wrapper, gspiceui, for ngspice as well as for GNU-cap. The user must still prepare the model, either with a text editor or gnetlist. Figure 4. gspiceui 6

7 geda pcb pcb is geda's printed circuit board layout program. Layouts may be developed from scratch, or schematics may be imported via gnetlist. Like gschem, there are a large number of standard symbols and footprints, or the user may develop his own, or modify existing footprints. Figure 5. pcb printed circuit board layout pcb can print a complete set of drawings for all layers, along with drill guides, screens, masks, etc. In addition, it can export images as Enacpsulated PostScript or png. It can also export to Gerber, G-code and Nelma. It can generate a complete bill of materials gerbv gerbv is a simple Gerber viewer. Individual layers or entire projects may be viewed. Layers may be combined into a single project. Layers may be reordered and color changed for optimal viewing. 7

8 Figure 6. Gerber viewer 2.2. qucs qucs, the "quite universal circuit simulator" is a simple schematic capture and simulator. The user can construct a schematic and runs a variety of simulations. There are a wide range of result displays available. SPICE netlists may be imported as subcircuits. Figure 7. Quite Universal Circuit Simulator 8

9 xcircuit 2.3. xcircuit xcircuit is yet another schematic capture and simple simulation application. xcircuit is unique in that it's native file format is Postscript. This allows for inclusion of any sort of custom graphic as well as hand-editing. xcircuit will also export SPICE netlists. Figure 8. xcircuit 2.4. gnucap gnucap is yet another circuit simulator. Unlike ngspice, LTspice, and dozens of others, gnucap is not based on the Berkeley SPICE code, although the input syntax is the same and gnucap can use SPICE models. Figure 9. gnucap Like ngspice, gnucap can use gspiceui as a GUI wrapper and results may be viewed with gwave. 9

10 2.5. kicad kicad is an integrated suite of electronic design applications similar to geda, but kicad is more tightly integrated. The suite lacks the full set of utilities of geda, however many of the applications have some nice features and a generally more polished user interface eeschema eeschema is the schematic capture component of kicad. eeschema lacks the rich component library of gschem, but it's search mechanism is better for locating components in a large library. Rather than hand-editing custom components as in gschem, eeschema has an integrated component editor. Figure 10. eeschema 10

11 kicad pcbnew pcbnew is the printed circuit board layout component of kicad. The comparison to pcb is similar to the comparison between gschem and eeschema. There are fewer supplied footprints, however there is a footprint editor, and bitmaps drawn with other tools may be imported as footprints. In addition, the conversion from a schematic, rather than being entirely scripted as in geda is assisted through a GUI. Figure 11. pcbnew One nice feature of pcbnew is the ability to view a 3D rendering of the board being designed. The rendering can be manipulated with the mouse to allow visual checking of component placement, clearances, etc. Figure 12. pcbnew - 3D Display 11

12 PCB Calculator kicad includes an interesting component called the "PCB Calculator". This little applications contains a number of tabs to assist in several common calculations, such has attenuators, transmission lines (including microstrips and waveguides), regulator design, etc. Figure 13. PCB Calculator 2.6. rcrpanel Sometimes embedded projects present some sort of user interface, often in the form of a fixed panel. These can often be laid out with tools such as Inkscape, but dials can be especially annoying to lay out with a drawing tool. rcrpanel is a command line tool specifically for laying out panels for electronic equipment. It knows the sizes of various devices, and can draw a variety of calibrated dials. Figure 14. Example Panel 12

13 Firmware 3. Firmware Firmware development in Linux is not too dissimilar from developing other software. There are assemblers, compilers and linkers, and a number of IDEs, each with it's own idea of what is "better". Perhaps one difference is in simulators. In ordinary software development the application is usually tested on the target hardware. However, in embedded applications the available peripherals are often limited, so there is a significant advantage to simulating the code on the host hardware where it can be easily stepped, simulated memory examined, etc Basic Tools Many of the IDEs rely on the same set of back end tools to perform compilation, assemble, linking, simulation and device programming. A sampling of these tools for the 8 bit PIC processors is described below gputils gputils is the assembler toolchain for 8 bit PICs. The toolchain covers almost all 8 bit PICs and is generally used as the back end for compilers and other tools. The applications included in gputils are: gpasm - PIC assembler gpdasm - disassembler gplib - librarian gplink - linker gpstrip - strip symbols from object files gpvc - COD file viewer gpvo - object file viewer The syntax is compatible with MPASM. Both the old and new COFF formats are supported sdcc sdcc, the "Small Device C Compiler" is an open source C compiler for a number of microcontroller targets. Included targets are the mcs51, gbz80, z80, ds390, ds400, 14 and 16 bit core PICs and hc08. Other ports are continually being added. The compiler produces assembler output for the target device assembler and can produce output for various memory models, where appropriate. Optimization are performed globally, and then on a target-specific basis. Many optimizations may be specifically disabled. Following the generation of the assembler code the native assembler and linker are invoked automatically. sdcc continues to be under heavy development so new features and targets are continually being added gcc ports There are a large number of ports of gcc to target various processors. Some of these are: AVR - also supported by binutils, a programmer, simulator, etc. Hitachi H8/300 - Only kernel building supported Motorola M68K, also a QEMU emulator and Amiga emulator 13

14 MIPS 64 - only kernel building supported Texas Instruments MSP gpsim gpsim is a full-featured simulator for 8 bit PIC devices. gpsim may be used as a command line application, with a GUI, or controlled remotely by other programs. Many of the IDEs use gpsim as a background simulator. Figure 15. gpsim gpsim supports additional modules to allow simulation of external devices. Included in gpsim are simple devices such as LEDs, seven segment displays, buttons, encoders, usarts, PAL video and I2C EEPROM. Additional third party devices available include LCD displays, both text and graphics picprog picprog is a serial port programmer for a large number of 8 bit PICs. It is frequently used as a back end for the various IDEs. Even though many designers have switched to USB programmers, the developer continues to add new PICs to the targets for this application Integrated Development Environments It seems like there are always multiple ways to do things, and PIC development is no exception. Of course, there is nothing preventing someone from using any of the basic toolchains with emacs, geany or whatever, but as always seems to be the case, we need multiple IDEs, too. Each has it's own spin on things, so there is no lack of choices piklab piklab is a very popular IDE for PIC development. It supports most 8-bit PIC parts and a good selection of 16-bit parts. It does not support PIC24E, dspic33e or any PIC32 devices. piklab supports a good range of serial and USB programmers. It supports a number of popular toolchains for PIC development (see below). 14

15 Integrated Development Environments Figure 16. piklab Although piklab supports the popular, open source toolchains, it also supports a large number of proprietary toolchains. Supported toolchains include: GPUtils BoostBasic BoostC BoostC++ C18 CC5X CCS dspicc MPC PIC30 PICC-18 PICC PICC Lite SDCC JAL JAL V2 Supported programmers: Generic TAIT programmer JDM classic PIC Elmer Velleman K8048 HOODMICRO ICD1 ICD2 Picdem Bootloader PICkit 1 15

16 PICkit 2 Picstart Plus Tiny Bootloader MPLAB-X MPLAB-X is Microchip's latest IDE. It is a complete, modern IDE with dramatically improved capabilities over the older, Windows-only, MPLAB 8. MPLAB-X is the only tool described here which is not FOSS. The supported toolchains are also proprietary, with the exception of SDCC. As a fully-featured, modern IDE, MPLAB-X features integration with revision control systems, CVS, Subversion and Mercurial (but not git!). It also integrates with team servers java.net and kenai.com. Issues may be tracked through integration with Bugzilla and JIRA. Figure 17. MPLAB-X MPLAB-X supports the Microchip toolchains, toolchains from some Microchip partners, and SDCC: CCS C Hi-Tech PICC mpasm PICBASIC SDCC C18 PICC18 asm30 C30 dspic Hi-Tech DSPICC C32 16

17 Integrated Development Environments MPLAB-X supports only current Microchip programmers and debuggers: ICD3 PICkit 2 PICkit 3 RealICE MCHV MICROSTICK SKDE PKOB MPLAB-X is Java based, and as such tends to be somewhat slow. However, it is very feature-rich and is far and away the most capable of the available microcontroller IDEs. MPLAB-X supports the full range of 8, 16 and 32 bit PICs and DSCs, and as Microchip's flagship IDE, is the first to support new devices as they become available ktechlab ktechlab is more focused on the simulation than on writing the code. The developer can draw a schematic and "load" the PIC code into the PIC on the schematic. The app can be then run on the virtual PIC, with the various wires changing color to indicate logic state, LEDs light, etc. there is also a scope to view waveforms. Figure 18. ktechlab 17

18 The only PIC supported is the PIC16F84. Supported toolchains: gputils sdcc Supported programmers: Odyssey picp PICProg pp XWisp prog pikdev pikdev is a very lightweight IDE focusing on simplicity. It uses the KText editor and as a result supports KText plugins. Figure 19. pikdev Supported programmers: Builtin pkp pk2 Tait 18

19 Integrated Development Environments P16PRO40 EPIC+ JDM PIC Elmer Velleman K8048 Baj's boot 555 Asix Piccolo ProPic2 EL Cheapo Monty-Robot HOODMICRO arduino arduino is a simple tool for Arduino sketches. The sketeches may be edited, compiled, verified and downloaded onto the board. A large number of example sketches are included. Figure 20. arduino 19

20 mcu8051ide mcu8051ide is a full-featured IDE for the Intel MCS-51 family. It includes an assembler, linker and simulator. The simulator has the ability to simulate external hardware as well. The IDE integrates with the SDCC. Figure 21. mcu8051ide Although mcu051ide does not support programming the chip directly, Atmel parts may be programmed with uisp Miscellaneous Tools pikloops PIC developers often require delay loops for various timing tasks. pikloops is a very simple application that accepts the desired delay time and the PIC's clock speed and generated code for the appropriate delay. 20

21 Revision History Figure 22. pikloops A. Revision History Revision 1.0 Thu Sep Add section on rcrpanel Remove draft tag John McDonough Revision 0.4 Mon Sep Add various gcc ports Add arduino Add mcu8051ide John McDonough Revision 0.3 Tue Apr Typos, cleaned up prose Improved gpsim screenshot John McDonough Revision 0.2 John McDonough Sun Apr

22 First draft prose Revision 0.1 Tue Apr Document skeleton Screenshots Initial prose John McDonough wb8rcr@arrl.net Revision 0 Wed Mar Initial creation of book by publican John McDonough wb8rcr@arrl.net 22