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AVR

AVR. Modern RISC architecture: Compact and FAST. Tuned for high level languages. Consistent architecture across entire line. Small AVR are subsets of larger chips: Same hardware and code works across all chips. I/O structure reduces need for external components.

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AVR

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  1. AVR • Modern RISC architecture: Compact and FAST. • Tuned for high level languages. • Consistent architecture across entire line. • Small AVR are subsets of larger chips: Same hardware and code works across all chips. • I/O structure reduces need for external components. • Flash based, ultra trivial downloading of code.

  2. AVR RISC Architecture • Single Cycle Instructions: 8mhz = 8mips. • Large register file (32). • Every register an accumulator. • 3 index register pairs • Register & IO are mapped in SRAM space.

  3. Typical Hardware Support • Real time clock • 10bit ADC • Analog Comparator • External interrupts • Pulse timing capture • EEPROM • USB/CAN/RF • Internal or External Oscillator/Clock • Brown Out Detector • One or more timers • Two or more PWM • One or more USART • I2C

  4. Tools • Atmel Studio: IDE & Simulator/debugger. • BASCOM: Basic compiler & IDE with programmer. • GNU C compiler (free, very high quality). • Third party C compilers vary from cheap to very expensive. • FLASH programmers are trivial to make.

  5. Availability & Price www.digikey.com has everything (single unit price): • Attiny26 (2k, ADC, USI, 2 PWM, 2 ports) $2.58 • ATmega16 (16k, ADC, etc, 4 ports) $7.74 • ATmega128 (128k, 6 ports, oodles of stuff) $16.34 • STK500 (development board) $79 • ICE200 (In circuit emulator) $100 • ATAVRISP (serial programmer) $29

  6. I/O Example: simple switch • No external parts

  7. Input Example: Trinary Input • Three states with one input. • Useful way to expand IO. • Switch internal resistor on/off to determine state of pin. • Off: If input high, then J1-2. • On: if low, then J2-3. • On: If high, then no jumper.

  8. Input example: Photo-detector • Schmitt trigger inputs on all lines. • No additional signal conditioning needed. • Stable, well defined trip points. • Basic circuit works well for Quadrature encoders.

  9. Input Example: Variable Input • Useful for parts without ADC. • Set pin to output, low to discharge capacitor. • Set pin to input, no pull-up. • Increment counter until input reads 1. • Linear conversion.

  10. Case Studies • BASCOM based multi-tasking Minisumo code in less than 2k • Dilbert II written with GCC in less than 6k • Gyrobot written with GCC in less than 6k • LCD user interface • PID based motion control • Sensor tasks managing tilt, gyro and wheel encoders • R/C Tether uses variable input (PC Joystick)

  11. Resources • www.barello.net/ARC • www.barello.net/Papers • www.avrfreaks.net • www.mcselec.com/download_avr • www.atmel.com/

  12. Cool projects & pages • http://www.mysunrise.ch/users/pfleury/index.html • http://instruct1.cit.cornell.edu/courses/ee476/ • www.barello.net/Robots • www.egnite.de (ethernet & web software) • www.avrfreaks.net (Academy tab, must register)

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