Embedded Systems

1. Embedded Systems University of Belgrade School of Electrical Engineering Department of Computer Science Authors: Gvozden Marinkovic mgvozden@eunet.yu Nikola Milanovic nikola99@eunet.yu Goran Timotic gogi@beotel.yu Ivan Sokic sokic@eunet.yu Prof. Dr. Veljko Milutinovic vm@etf.bg.ac.yu

2. Introduction • Design • Components • Microcontrollers • Communication • Examples • ARMs • PIC MCUs

3. Design • Specification • Circuit Design • Printed Circuit Board Layout • Firmware • Pilot Run • Production Source AirBorn Electronics

4. Electronic Design Flowchart Source AirBorn Electronics

5. Specification • Starts as collection of ideas that describe a device or product • Specifications go through two phases • first phase they describe the product as desired: must-have, bells and whistles features • second phase they describe the product as required:describes the product as it is required to be produced Source AirBorn Electronics

6. Specifying New Design • Give your project a name • Keep project name short, it saves time • Describe your project (Opening Statement) • Keep the first description short • First sentence should summarize the whole function of the project • Describe or name equipment, devices or interfaces • Describe your projects market • Describe the market need your product fulfills • Estimate the production volume Source AirBorn Electronics

7. A Specification reads like a list of project features,describing the unit, and will usually include: Specification:Technical Ingredients • Inputs • Controls • Outputs • Indicators • Functions Modes of operation • Power Supply • Communications • Protection • Fail safes andreplaceable parts • Connector types • Physical format and size Source AirBorn Electronics

8. Part 1 Circuit Design • Maps out the electronics and connectionsin the most readily readable form • The designer needs to do background work: • research specifications of components • research interaction between components(especially timing and loading) • research physical packages • research arrangement of connector pinouts • The finished circuit diagram is the main document for the design Source AirBorn Electronics

9. Part 2 Circuit Design • Circuit diagram is a strict document • A circuit diagram must reflect the actual constructionof the printed circuit board which is made from it • Printed circuit board CAD and Schematic CADare tied together through a Net-check • The circuit diagram references each part on the PCBwith a designator and pin numbers for each connection Source AirBorn Electronics

10. Printed Circuit Board Layout • Connections on the PCBshould be identical tothe circuit diagram • Circuit diagram is arrangedto be readable • PCB layout is arrangedto be functional • PCB layout can be performed: • manually (using CAD) • in combination withan Autorouter Source AirBorn Electronics

11. Part 1 Methods of PCB construction • Conventional • Rigid PCB of thickness 1.6mm • Wire-leaded componentsmounted on only one sideof the PCB • All the leads through holes, soldered and clipped. • Easier to debug and repair than Surface mount Source AirBorn Electronics

12. Part 2 Methods of PCB construction • Surface Mount Technology (SMT)devices (SMD) • PCB with tag-leaded componentssoldered flush to PCB pads • Holes are still needed on the PCB, not where the component leads are attached • Generally smaller than conventional • Generally more suited to automated assembly than conventional Source AirBorn Electronics

13. Part 3 Methods of PCB construction • Surface mount and conventional mix • Most boards are a mix ofsurface mount andconventional components • Disadvantages becausethe two technologies require different methods ofinsertion and soldering Source AirBorn Electronics

14. Part 4 Methods of PCB construction • Double sided Laminate • Tracks on both sides, normally with PTH holesconnecting circuitry on the two sides together • Double sided component Assembly • Mounting components on both sides of the PCB • Normally only surface mount circuitrywould be mounted on both sides of a PCB Source AirBorn Electronics

15. Part 5 Methods of PCB construction • Multi-layer • PCB Laminate manufacturedwith more than two layers of copper tracks,by using a sandwich construction • Cost of the laminate reflects the number of layers • Used to • route complicated circuitry • distribute the power supplymore effectively Source AirBorn Electronics

16. Part 6 Methods of PCB construction • Gold plated • Certain areas on a PCB may be gold plated for use as contact pads • Flexible PCB • Technique used extensively with • membrane keyboards • combination connector/circuit boards • circuit boards to fit in awkward shapes Source AirBorn Electronics

17. Part 7 Methods of PCB construction • Chip On Board (COB) • IC is attached direct to a PCB • Bond out wires from the IC connect directly to PCB lands • Chip is covered with a black blob of epoxy • Used mostly with very high volume, cost sensitive applications Source AirBorn Electronics

18. Part 8 Methods of PCB construction • Phenolic PCB • Phenolic is a cheaper PCB laminate material • Daughterboard • Circuit board mounted to another circuit board Source AirBorn Electronics

19. Part 1 Printed Circuit Board Etching • CAD File processing • PCB CAD files are sent tothe PCB Manufacturer • PCB manufacturer inspects the files, making a drill list and adding identification • CAD files are processed andsent to a photoplotterto turn into film artwork Source AirBorn Electronics

20. Part 2 Printed Circuit Board Etching • Laminate drilling and electroplating • Laminates are drilled with holes • Drilled laminates are coatedin a chemical to enhance electroplating of holes • Laminates are put ina copper plating bath,all the holes are electroplated • This connects pads on opposite sides of the PCB, electrically Source AirBorn Electronics

21. Part 3 Printed Circuit Board Etching • Laminate etching • The laminates are coated with a UV-sensitive photo-resist • The track pattern is imaged onto each side of each PCB,using the photoplots and UV light • The photo-resist is developed,leaving photo-resist only where copper is required • The laminates are put in acid,to etch away unrequired copper, forming the track pattern • The bare copper PCB, with tracks and pads now finished,is cleaned Source AirBorn Electronics

22. Part 4 Printed Circuit Board Etching • Laminate solder masking and tinning • The bare copper PCB is silkscreened with a solder mask (usually green) • The solder mask is dried or cured • The PCB is tinned - solder is applied to exposed pads • The PCB is levelled - bumps in the solder is made flat by using hot air or hot oil Source AirBorn Electronics

23. Part 5 Printed Circuit Board Etching • Final stages • The PCB is silkscreened with component identification lettering (usually white) • The silkscreen legendis dried or cured • Any final drilling is done of holes that are not to be plated through, any routing is done, and the laminate is cut into individual printed circuit boards Source AirBorn Electronics

24. PCB Assembly • Assemblies should be • maintainable • repairable • durable; and • easy to install Source AirBorn Electronics

25. Part 1 PCB Documentation • Front Cover • Title, date, version number, customer details, project features • Schematic • ECO Sheet • Details of any circuit modifications • Bill of material • The parts list • Parts key • A glossary of the part number abbreviations, with package sizes,lead spacing, tolerance notes and preferred types Source AirBorn Electronics

26. Part 2 PCB Documentation • Front panel artwork • Manufacturing notes • Contains the notes relating to previous production runs- for instance problems encountered, methods of testing • Drilling diagram • Showing the positioning and size of every hole on the PCB • Actual size PCB overlay • Showing the positioning and identification of the PCB components • The plan is printed actual size to allow components to be placed against it to check for fit Source AirBorn Electronics

27. Firmware • The major steps in Firmware design are: • Program Specification • Program Design • Writing code • Program Test Source AirBorn Electronics

28. Program Specification • The specification for the Electronic Product being designedwill usually also be the specification for the programming required • The program specification will required the writer to go into substantial detail about how the product actually operates,and how it is used • A thorough program specification leads straight in toFlow charts and timing diagrams,which are components of Program Design Source AirBorn Electronics

29. Program Design • The program design stage lays out the structure andalgorithms of the firmware • The structure and algorithms may be laid out as: • flowchart • timing diagram • description of a protocol • memory map; or • equation Source AirBorn Electronics

30. Writing Code • If the program is well specified andthe algorithm design stage has been thorough,the actual code writing stage can become almost mechanical • By defining the software at the outset, before code is written,a much more defined, integrated, set of code can be produced • The extra space occupied by comments costs nothing,and if the comments are well laid outthere is no possibility that they can detractfrom understanding the code Source AirBorn Electronics

31. Program Test • Divide the testing of the design into small, autonomous units • It is easier to detect faultsbefore they are compounded by other factors • Program testing requires getting diagnostic data out of the target, for analysis • By emulation tools,or through the hardware itself (for instance a serial port) Source AirBorn Electronics

32. Pilot Run • To test the product further, a Pilot run normally follows the prototyping stage • Small quantity of units are field trialed in a beta test • Opportunity to assess the manufacturability of the design,and the usability of the documentation Source AirBorn Electronics

33. Production • Following the pilot run there will likely be changesto the firmware, and possibly the circuit design,as the unit develops into a stable, final product • This process is controlled by ECO’s and version numbers • The cost, style of design of the final production, is heavily influenced by the number of units manufactured Source AirBorn Electronics

34. Components • Capacitors • Resistors • Transistors • Diodes • Oscillators and Crystals • AD Converters • DA Converters • LCD (Liquid Crystal Display) • Operational Amplifier • Sensors and Transducers

35. Oscillators and Crystals • Feedback Oscillators • Loop Gain • How Feedback Oscillators Work? • Quartz Crystal • Crystal Parameters • Equivalent Circuit • Load Capacitance • “Series” vs. “Parallel” Crystals • Frequency Tolerance

36. AD Converters • Converts analog input to a digital value and outputs it as serial or parallel data • Basic attributes • number of channels for analog input • approximation type • resolution (number of bits) • conversion speed • serial or parallel output • operating temperature range • errors (linearity, differential linearity, total)

37. DA Converters • Converts digital input to an analog value and outputs it as a DC voltage • Basic attributes • conversion method • output settling time • analog output sink/source current • operating temperature range

38. LCD (Liquid Crystal Display) • Used in low power devices (voltage 2-3V) • Layer of liquid crystal (10-12m thick) is formed between two glass plates • When applied, electrical field polarizes molecules of liquid crystal and the chosen segment becomes visible • Beside low power devices, LCD is becoming a standard option for desktop monitors - flat panel TFT LCD (clearer picture with higher resolution) • Problem: viewing angle

39. Operational Amplifier • Realization with differential amplifier (IC or discrete logic) • Circuits with negative or positive feedback (amplifiers and oscillators) • Basic parameters: • gain • input and output resistance • bandwidth (frequency characteristics) • voltage and current drift • max. output current

40. Sensors and Transducers • Classification: • physical property (piezoelectric, photovoltaic, etc.) • function (measurement of length, temperature, etc) • Radiant, gravitational, mechanical, thermal, electrical, magnetic, molecular, atomic, nuclear • The signal is fed into an input transducer, which changes the form of energy, usually into electrical. • A modifier, usually an amplifier, and an output transducer then convert the energy into a form to be displayed or recorded.

41. Sensors and Transducers • The following is a diagram representative of this system: • Three basic types of transducers are: • self generating • modulating • modifying

42. Microcontrollers • Specially designed microprocessors • It is small on chip computer • Highly integrated chipincludes all or most parts needed for controller • A typical microcontroller has: • bit manipulation • easy and direct access to I/O • quick and efficient interrupt processing • Microcontroller drastically reduces design cost

43. Worldwide Microcontroller shipments- in millions of dollars - Source WSTS & ICE

44. Worldwide Microcontroller shipments- in millions - Source WSTS & ICE

45. Applications • Appliances(microwave oven, refrigerators, television and VCRs, stereos) • Computers and computer equipment(laser printers, modems, disk drives) • Automobiles(engine control, diagnostics, climate control), • Environmental control(greenhouse, factory, home) • Instrumentation • Aerospace • Robotics, etc...

46. Flavors • 4, 8, 16, or 32 bit microcontrollers • specialized processors include features specific for • communications, • keyboard handling, • signal processing, • video processing, and other tasks.

47. Part 1 Popular Microcontrollers • 8048 (Intel) • 8051 (Intel and others) • 80c196 (MCS-96) • 80186,80188 (Intel) • 80386 EX (Intel) • 65C02/W65C816S/W65C134S (Western Design Center) • MC14500 (Motorola)

48. Part 2 Popular Microcontrollers • 68HC05 (Motorola) • 68HC11 (Motorola and Toshiba) • 683xx (Motorola) • PIC (MicroChip) • COP400 Family (National Semiconductor) • COP800 Family (National Semiconductor) • HPC Family (National Semiconductor) • Project Piranha (National Semiconductor)

49. Part 3 Popular Microcontrollers • Z8 (Zilog) • HD64180 (Hitachi) • TMS370 (Texas Instruments) • 1802 (RCA) • MuP21 (Forth chip) • F21 (Next generation Forth chip)

50. Part 1 Programming Languages • Machine/Assembly language • Interpreters • Compilers • Fuzzy Logic and Neural Networks