Deploy task-specific microcontrollers to simplify complex designs

Ideal output of a 100 kHz V/F converter (watchdog disabled).

Ideal output of a 10 kHz V/F converter (watchdog disabled).

Duty Cycle Generator

Duty Cycle Generator Block Diagram

The solution's duty cycle generator block is responsible for creating a 50% duty cycle output. This is an optional feature - the output of the NCO could be used directly, but doing so would increase the variability of the duty cycle.

The generator is implemented using a Configurable Logic Cell (CLC). A CLC is a small block of configurable logic, similar to a cell in a Field Programmable Gate Array (FPGA). A CLC can be used as a discrete logic gate (such as AND-OR or OR-XOR), or it can be configured as a latch or a flip-flop. In this solution, the CLC is implemented as a JK flip-flop with reset. J and K are held at logic high. The output oscillator block is used as the clock for the flip-flop. Each input clock pulse causes the output to toggle, resulting in a 50% duty cycle. Note: Frequency jitter in the output oscillator block will have an effect on the duty cycle.

Timer 6 is used as an astable "watchdog" timer. If the output does not generate an edge (rising or falling), the timer will overflow and the resulting clock pulse will be sent to the CLC, which controls the lower limit of the output frequency range. Instead of reaching DC, the output rolls over to half the timer frequency (6 Hz output).

Key points of the solution

This example shows that to create core-independent functionality using hardware peripherals, an external integrated circuit must usually be used. One of the biggest advantages of this configuration is that the operation of the peripherals can be set up in software, making it easy to adapt the example to the end application. Due to the large number of peripherals used, the PIC18-Q43 family of MCUs was chosen to implement this example.

For more information on this example, see the README document in the examples repository. Additionally, the examples repository contains an implementation of a frequency-to-voltage converter that can be implemented on the same device as the voltage-to-frequency converter.

Summarize

While high-performance microcontrollers and microprocessors have their place, 8-bit and 16-bit MCUs can be used to perform small, specialized tasks. These tasks are not necessarily complex, but they can be time-consuming or time-critical. With a lighter workload, 32-bit devices can have simpler implementations, resulting in higher reliability, less memory usage, and lower power consumption.