platform-gpio.hh

#pragma once
#include <cdefs.h>
#include <stdint.h>
 
/**
 * Represents the state of the Sonata's joystick.
 *
 * Note, that up to three of the bits may be asserted at any given time.
 * There may be up to two cardinal directions asserted when the joystick is
 * pushed in a diagonal and the joystick may be pressed while being pushed in a
 * given direction.
 */
enum class SonataJoystick : uint8_t
{
    Left    = 1 << 0,
    Up      = 1 << 1,
    Pressed = 1 << 2,
    Down    = 1 << 3,
    Right   = 1 << 4,
};
 
/**
 * A Simple Driver for the Sonata's GPIO.
 *
 * Documentation source can be found at:
 * https://github.com/lowRISC/sonata-system/blob/1a59633d2515d4fe186a07d53e49ff95c18d9bbf/doc/ip/gpio.md
 *
 * Rendered documentation is served from:
 * https://lowrisc.org/sonata-system/doc/ip/gpio.html
 */
struct SonataGPIO
{
    uint32_t output;
    uint32_t input;
    uint32_t debouncedInput;
    uint32_t debouncedThreshold;
    uint32_t raspberryPiHeader;
    uint32_t raspberryPiMask;
    uint32_t arduinoShieldHeader;
    uint32_t arduinoShieldMask;
 
    /**
     * The bit index of the first GPIO pin connected to a user LED.
     */
    static constexpr uint32_t FirstLED = 4;
    /**
     * The bit index of the last GPIO pin connected to a user LED.
     */
    static constexpr uint32_t LastLED = 11;
    /**
     * The number of user LEDs.
     */
    static constexpr uint32_t LEDCount = LastLED - FirstLED + 1;
    /**
     * The mask covering the GPIO pins used for user LEDs.
     */
    static constexpr uint32_t LEDMask = ((1 << LEDCount) - 1) << FirstLED;
 
    /**
     * The output bit mask for a given user LED index
     */
    constexpr static uint32_t led_bit(uint32_t index)
    {
        return (1 << (index + FirstLED)) & LEDMask;
    }
 
    /**
     * Switches off the LED at the given user LED index
     */
    void led_on(uint32_t index) volatile
    {
        output = output | led_bit(index);
    }
 
    /**
     * Switches on the LED at the given user LED index
     */
    void led_off(uint32_t index) volatile
    {
        output = output & ~led_bit(index);
    }
 
    /**
     * Toggles the LED at the given user LED index
     */
    void led_toggle(uint32_t index) volatile
    {
        output = output ^ led_bit(index);
    }
 
    /**
     * The bit index of the first GPIO pin connected to a user switch.
     */
    static constexpr uint32_t FirstSwitch = 5;
    /**
     * The bit index of the last GPIO pin connected to a user switch.
     */
    static constexpr uint32_t LastSwitch = 13;
    /**
     * The number of user switches.
     */
    static constexpr uint32_t SwitchCount = LastSwitch - FirstSwitch + 1;
    /**
     * The mask covering the GPIO pins used for user switches.
     */
    static constexpr uint32_t SwitchMask = ((1 << SwitchCount) - 1)
                                           << FirstSwitch;
 
    /**
     * The input bit mask for a given user switch index
     */
    constexpr static uint32_t switch_bit(uint32_t index)
    {
        return (1 << (index + FirstSwitch)) & SwitchMask;
    }
 
    /**
     * Returns the value of the switch at the given user switch index.
     */
    bool read_switch(uint32_t index) volatile
    {
        return (input & switch_bit(index)) > 0;
    }
 
    /**
     * Returns the state of the joystick.
     */
    SonataJoystick read_joystick() volatile
    {
        return static_cast<SonataJoystick>(input & 0x1f);
    }
};