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Questions and Answers
What effect does increasing the duty cycle percentage have on the output signal?
How is the frequency of a PWM signal calculated?
In the provided code example, what is the duty cycle when the delay is set to 10 microseconds for both HIGH and LOW states?
Which of the following statements best describes the duty cycle in a PWM signal?
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What components are necessary for creating a PWM signal manually, as illustrated in the code?
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What is the primary purpose of the mode described for generating delays?
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In the context of the external counter mode, what does the unit count?
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Which of the following statements is NOT true about the precise time counting machine mode?
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What is a potential use of the external counter feature?
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How do the functions of the precise time counting machine and the external counter differ?
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What is the primary use of Pulse Width Modulation (PWM)?
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How many Timer/Counters does the ATmega328p have?
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What does the Output Compare Register (OCR) do in a Timer?
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Which statement about Timer 0 on the ATmega328p is true?
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Which of the following is NOT an application of PWM?
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What is the recommended method for passing data between an ISR and the main program?
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Why must caution be exercised when reading a variable with a size that is a multiple of MCU SRAM word size?
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Which type of variable is NOT suitable for passing data between an ISR and the main program?
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What is the risk associated with using variables to pass data between the ISR and the main program?
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Which variable type is specifically highlighted as necessary for handling ISR data passing?
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What advantage does Flash memory offer for storing constants according to the context provided?
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In the provided code snippet, what function is used to read a byte from Flash memory?
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What is the purpose of the for loop in the code example?
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What type of data is being stored in Flash memory in the given example?
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What is the likely reason for using the PROGMEM keyword in the declaration of a_string?
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Study Notes
Pulse Width Modulation (PWM)
- PWM is used to control speed and light intensity.
- Duty Cycle: The ratio of "on" time to the total period of a PWM signal. A higher duty cycle corresponds to a larger output signal.
- Period/Duration: The length of one complete cycle of a PWM signal.
- Average Voltage: The average voltage output by a PWM signal. It is determined by the duty cycle.
PWM Period and Duty Cycle
- The frequency of a PWM signal is the reciprocal of the period.
- The duty cycle can be calculated as the ratio of the "on" time to the total period, expressed as a percentage.
How to Create PWM
- Manually using delay functions:
- The
delayMicroseconds()function is used to create precise delays. - The duty cycle is determined by the ratio of the "on" time to the total period, including both "on" and "off" times.
- The
- Using Timer/Counters:
- Timer/Counters are dedicated hardware modules within microcontrollers.
- ATmega328p has two 8-bit Timer/Counters and one 16-bit Timer/Counter.
Timer 0 (8-bit timer)
- The Output Compare Register (OCR) is used to set the last count in the timer.
- The output compare flag (OCF) is set when the timer count reaches the value in the OCR.
- Global and volatile variables are used to pass data between interrupt service routines (ISRs) and the main program.
- Store data in Flash Memory to mitigate issues with ISR variables.
Programming with Flash Memory
- Constants can be stored in Flash Memory.
- Using
PROGMEMkeyword stores data in Flash Memory. - Use
pgm_read_byte_near()function to access stored data. - The
strlen_P()function works with strings stored in Flash Memory.
Benefits of Storing Constants in Flash Memory
- Flash memory is non-volatile, meaning the data remains even when power is off.
- Data stored in Flash Memory is typically read-only, protecting from accidental writes.
- Flash memory is more efficient for storing large amounts of data compared to RAM.
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Description
This quiz covers the fundamental concepts of Pulse Width Modulation (PWM), including duty cycle, period, and average voltage output. You'll learn how these parameters influence the control of speed and light intensity in various applications. Test your understanding of creating PWM signals using manual delay functions and Timer/Counters.
