platform-pwm.hh

#pragma once
#include <debug.hh>
#include <stdint.h>
#include <utils.hh>
 
namespace SonataPulseWidthModulation
{
    /**
     * A driver for Sonata's Pulse-Width Modulation (PWM).
     *
     * Documentation source can be found at:
     * https://github.com/lowRISC/sonata-system/blob/97a525c48f7bf051b999d0178dba04859819bc5e/doc/ip/pwm.md
     *
     * Rendered documentation is served from:
     * https://lowrisc.github.io/sonata-system/doc/ip/pwm.html
     */
    struct Output : private utils::NoCopyNoMove
    {
        /**
         * The duty cycle of the wave, represented as a width counter. That
         * is, the number of clock cycles for which the signal will be on. The
         * duty cycle as a percentage is (duty cycle / period) * 100.
         */
        uint32_t dutyCycle;
 
        /**
         * The period (width) of the output block wave, set with the number of
         * clock cycles that one period should last. The maximum period is 255
         * as only an 8 bit counter is being used.
         */
        uint32_t period;
 
        /*
         * Sets the output of a specified pulse-width modulated output.
         *
         * @param period The length of the output wave represented as a counter
         * of system clock cycles.
         * @param dutyCycle The number of clock cycles for which a high pulse is
         * sent within that period.
         *
         * So for example `output_set(0, 200, 31)` should set a 15.5% output.
         * For a constant high output (100% duty cycle), set the dutyCycle >
         * period.
         */
        void output_set(uint8_t period, uint8_t dutyCycle) volatile
        {
            this->period    = period;
            this->dutyCycle = dutyCycle;
        }
    };
 
    /// A convenience structure that can map onto multiple PWM outputs.
    template<size_t NumberOfPwms = 6>
    struct Array
    {
        Output output[NumberOfPwms];
 
        template<size_t Index>
        volatile Output *get() volatile
        {
            static_assert(Index < NumberOfPwms, "PWM index out of bounds");
            return output + Index;
        }
    };
 
    /**
     * There are six general purpose PWM outputs are general purpose that can be
     * pinmuxed to different outputs.
     */
    using General = Array<6>;
    /// There is one dedicated PWM for the LCD backlight.
    using LcdBacklight = Output;
} // namespace SonataPulseWidthModulation