Auto-Chromatic Instrument Tuner
System Level Block Diagram

1.Microphone:

• Inputs: Physical audio signals from environment
• Outputs: Electrical representation of audio signals to the Amplifier
• Functional Description: Picks up an acoustic signal and converts it to an electrical signals
• Relation to Overall System: Main system input - entry point for unknown played pitch

  2.Amplifier:

• Inputs: Electrical audio signal from  Microphone and Automatic gain control
• Outputs: Amplified audio signals to  Threshold Detector
• Functional Description: Increases the amplitude of the electrical audio signals to a more easily processed level
• Relation to Overall System: Matching network and gain block between 1) Microphone and 3) Threshold Detector

  3.Threshold Detector:

• Inputs: Amplified audio signal from the Amplifier
• Outputs: TTL level pulses with rising and falling edges corresponding to fundamental period of input signal to the Timer/Counter and Automatic gain control signal
• Functional Description: Converts input signal to fundamental frequency information
• Relation to Overall System: Extracts the fundamental frequency from a complex audio waveform

4. Automatic Gain Control

• Inputs: Data from the Threshold Detector
• Outputs: Takes information from the Threshold Detector and feeds back to the amplifier
• Functional Description: Helps regulate the gain and provides more stability in the system
• Relation to Overall System:  Feeds back the signal from the Threshold Detector to the Amplifier

  5.Timer/Counter:

• Inputs:

• Outputs:

• Functional Description: Counts the time between fundamental periods, triggers overflow if count overflows
• Relation to Overall System: Quantitatively measures the period of the fundamental frequency of the original signal

  6.Clock:

• Inputs: None
• Outputs: Main Clock to Divide By 2 Tree and  Microprocessor
• Functional Description: Provides the clock signal for all components that require one
• Relation to Overall System: Provides required timing information so that the played pitches can be analyzed with respect to a consistent reference; synchronizes microprocessor and logic timing

  7. Divide By 2 Tree:

• Inputs: Main timing signal from Clock
• Outputs: Count Clock to Timer/Counter
• I/O: Divide by 2n control to/from Microprocessor
• Functional Description: Divides the Main Clock by the nth power of 2 to give Count Clock.
• Relation to Overall System: Permits measurement of a wide variety of frequencies with maximum resolution, since pitches are based on octaves, which is a base 2 system (e.g. all "C"s have frequencies which are related by multiplying or dividing by a power of 2

  8. Power / Mode Switch:

• Inputs:

• Outputs:

• Functional Description: Controls power to the system and selects the operating mode
• Relation to Overall System: Allows the user to turn the system on and off and select the operating mode

  9. DC Power:

• Inputs: DC Power Source
• Outputs: DC Power to  Power / Mode Switch
• Functional Description: Provides the electrical power for the entire system
• Relation to Overall System: Connection for battery, power supply, etc. to power the system

  10. Pitch Selector:

• Inputs: Button pushes by user
• Outputs: Pulses from switches
• Functional Description: Allows the user to select a pitch from C0 to B9 (C in the 0th octave to B in the 9th octave)
• Relation to Overall System: Allows to the user to select pitches for Manual Tuning and Audible Reference Pitch modes.

• I/O: Frequency Reference Data to/from Microprocessor
• Functional Description: Contains reference data for frequencies of one full octave
• Relation to Overall System: Provides the system with a reference to which it can compare the frequency of the played pitch; only one octave is needed since the frequencies can simply be multiplied or divided by powers of two (by simple binary left and right shifts) to get the other octaves

 12. Function Generator:

• I/O: Function Generator Control to/from Microprocessor
• Outputs: Electrical Audio Output Waveform to Speaker Driver
• Functional Description: Generates audio waveforms
• Relation to Overall System: Generates waveforms for selected pitches in Audible Reference Pitch mode

 13. Speaker Driver:

• Inputs: Electrical Audio Output Waveform from Function Generator
• Outputs: Speaker Audio Signal to Speaker
• Functional Description: Amplifies the output audio signal to drive a speaker
• Relation to Overall System: Provides the necessary current and voltage levels to allow the speaker to produce selected pitched audibly in Audible Reference Pitch mode

• Inputs: Speaker Audio Signal from Speaker Driver
• Outputs: Acoustic Signal to environment
• Functional Description: Converts electrical energy into acoustic energy
• Relation to Overall System: Allows selected pitches to be heard

• I/O: Display Control to/from Microprocessor
• Outputs:

• Functional Description: Controls all of the display elements based on information from the Microprocessor.
• Relation to Overall System: Controls devices which display necessary information to the user

 16. LCD/LED Bar Indicator

• Inputs: Analog and Digital Tuning Error Signal from Display Control
• Outputs: Visual indicator (LED’s and meter) to User
• Functional Description: Lights LCD/LED’s based on tuning error.
• Relation to Overall System: Gives the user visible feedback on the tuning of the played pitch

 17. Pitch Indicator:

• Inputs: Pitch Display Data from Display Control
• Outputs: Visual indicator (3 seven segment LEDs) to User
• Functional Description: Displays characters on the seven segment displays indicating a pitch
• Relation to Overall System: Tells the user what pitch is being tuned or played on the speaker

 18. Microprocessor:

• Inputs:

• I/O:

• Functional Description: Executes code (see flow chart) which controls subsystems, reads inputs, performs all calculations, controls outputs, etc
• Relation to Overall System: Heart of the system; determines all operating characteristics of the system according to user input.