STM32 – PWM, ADC, FFT, LCD

• What factors affect the choice of sampling frequency for the ADC?

  ·        Signal Band width

  ·        Nyquist Shannon sampling frequency - especially when the sampling frequency has to be at least 2x the max frequency.

  ·        ADC resolution
• The STM programming made significant use of the HAL library. Why do you think this was and what advantages does it offer?

  
  

  ·        This library simplifies the programming process. It does so by provide a consistent interface which makes it easier to port code across different microcontrollers.

  ·        This helps in portability and ease of development.

  ·        Optimises code size and promotes code reuse.
• The ADC and PWM made use of interrupt functions. What is an interrupt and give an example of how they were used?

  ·        Interrupt is a mechanism that allows the microcontroller to stop what its doing and perform a different specific task and then go back to the original task.

  ·        Example: In ADC a interrupt may be called when a conversion has been completed, in order for the processor to read the result
• Explain what is an FFT? How might you implement this on a micro-controller such as the STM32?

  ·        FFT is an algorithm that analyses the frequency content of a signal

  ·        In STM32 there various libraires like the microcontroller software which has multiple functions that help enhance the calculation of FFT

  ·        CMSIS DSP – Cortex microcontroller software interface standard digital signal processing

  ·        Libraries optimise functions for FFT calculations
• The LCD module supports both 4-bit and 8-bit modes. In terms of advantages and disadvantages, what are the differences between these two modes?

  ·        The 8-bit mode has a faster data transfer and can send more data at once. However, it requires more pins

  ·        A 4-bit mode requires less pins therefore conserves pins. However, the speed of data transfer might be less than the 8bit.
• Explain the different types of ADC implementation you can do with the STM32 microcontroller you used?multiple

  ·        Single mode

  ·        Continues conversion.

  ·        Scan mode

  ·        In single mode the ADC samples one channel continuously, while in scan mode the ADC samples over multiple channels sequentially

  ·        Continuous conversion mode ADC continuously and repeatedly samples input signal without any external trigger or intervention
• How do you calculate the sampling frequency of the ADC used in the STM32 microcontrollers?

  ·        Sampling frequency = 1/sampling time+ conversion

  ·        Where sampling time is the time taken to acquire the analogue signal

  ·        Where conversion time is the time taken to convert the analogue signal into a digital value

  ·        This can then be implemented in the ADC configuration in the software