Embedded System Design Study Notes

Introduction to Embedded System Design

  • Presented by Dhananjay V. Gadre, Associate Professor ECE Division, Netaji Subhas University of Technology, New Delhi.
  • Presented by Badri Subudhi, Assistant Professor, Electrical Engineering Department, Indian Institute of Technology, Jammu.
  • Focus on physical interfacing in embedded systems.

Driving LEDs (Or Other Loads)

Constant Current Low Side Driver

  • Components involved:
      - VCC: Supply voltage.
      - Microcontroller: Controls the current through the load.
      - Resistors (R1, R2): Set the current levels.
      - Diodes (D1, D2): Indicator LEDs for showing activity.
  • Connection diagram illustrates the basic setup with the microcontroller controlling the transistor (T1) to drive the LED.

High Side Driver

  • Configuration allows for connection above the load.
  • Components involved:
      - VCC: Supply voltage for the load.
      - Resistors (R1, R2, R3, R4): Control current and protect components.
      - Microcontroller: Integrates control logic to switch power.
  • Setup allows for driving LEDs while maintaining higer voltage across the load.

Constant Current High Side Driver

  • Similar setup as high side driver.
  • Emphasizes constant current control for LEDs through feedback mechanisms.
  • Resistors at the base of the transistor (T1) ensure stable operation.

Controlling LEDs

  • Different configurations for controlling multiple LEDs:
      - If N pins are used for N LEDs, direct control is achievable.
      - Multiplexing allows for reduced pins leading to up to N24\frac{N^2}{4} LEDs.
      - Charlieplexing optimizes pin usage enabling control of Nimes(N−1)N imes (N - 1) LEDs including combinations.

Driving Seven Segment Displays

Anode Driver Circuit

  • Configuration involves controlling individual segments of the display (8 segments).
  • Utilizing both common cathode connections and specific resistances for current control.

Low Side Driver Circuit

  • ULN2803 utilized as interfacing for driving segments of the display.
  • Detailed pin connection diagram showing resistance values and power configurations.

High Side Driver Circuit for Seven Segments

  • Using UDN2981A to UDN2984A series for high side control.
  • Each segment or digit of the display is driven by the respective output pins.

Both Side Switching Techniques for Displays

Driving Seven Segment Displays

  • Utilize microcontroller switching mechanism to alternate between outputs.
  • Configured for both high side and low side operations using appropriate driver ICs (e.g., ULN2803).

Driving Dot Matrix Displays

  • Similar principles applied as with seven segment displays.
  • Q1-Q4 transistors used to switch current through rows/columns at corresponding timings.

Alternate Method of Both Side Switching

  • Explores variations in driving techniques for displays using optimized switching arrangements.

Charlieplexing

  • A technique for driving LEDs that allows individual LED control using minimal pins.
  • For N available pins, it allows control of up to Nimes(N−1)N imes (N - 1) LEDs, maximizing efficiency.

Digital to Analog Conversion

Using PWM

  • Represents analog values through varying pulse-width modulation techniques.
  • Examples of specific duty cycles shown: 20%, 40%, 50%, 80%. Demonstrates how time domain affects output levels.

Using R-2R Ladder DAC

  • R-2R ladder configuration allows for binary weighted voltage division creating analog signals.
  • Specify resistor values:
      - R1, R3, R5, R7, R8 = 20K
      - R2, R4, R6 = 10K
  • Outputs voltage scale from digital binary inputs.

Liquid Crystal Displays (LCDs)

Character Displays

  • Operate at +Vcc ranges of 4.5-5.5V (compatible ICs like Hitachi HD).
  • Specifications for connections including RS, R/W signals and controlling brightness via LED configurations.

Graphics Displays

  • Operate at lower voltage levels of +Vcc (2.7-3.3V).
  • Nokia graphics LCD (48x84 pixels) configuration includes essential power, data, and clock signals for drive control.

Buzzer and Speaker

  • Buzzer typically uses an in-built driver to produce sound.
  • External driver configuration may involve tuned circuits activated by timers for controlled sound production.
  • Speaker configurations utilize transistors and timers for audio amplification.

Ultrasonic Sensors

  • Utilize piezoelectric elements known for strong resonance properties in various applications.
  • Common applications in automotive and distancing measurements.

Haptic Feedback Devices

  • Haptic systems deploying DC motors with eccentric loads for tactile interaction feedback.

Conclusion

  • Thank you for your attention!