ardupilot/libraries/AP_HAL_Linux/RCInput_RPI.h

#ifndef __AP_HAL_LINUX_RCINPUT_RPI_H__
#define __AP_HAL_LINUX_RCINPUT_RPI_H__

#include "AP_HAL_Linux.h"
#include "RCInput.h"
#include <signal.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdarg.h>
#include <stdint.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <assert.h>
#include <queue>


enum state_t{
    RCIN_RPI_INITIAL_STATE = -1,
    RCIN_RPI_ZERO_STATE = 0,
    RCIN_RPI_ONE_STATE = 1
};


//Memory table structure
typedef struct {
    void **virt_pages;
    void **phys_pages;
    uint32_t page_count;
} memory_table_t;


//DMA control block structure
typedef struct {
  uint32_t info, src, dst, length,
    stride, next, pad[2];
} dma_cb_t;

class Memory_table {
// Allow RCInput_RPI access to private members of Memory_table
friend class Linux::RCInput_RPI;
  
private:
    void** _virt_pages;
    void** _phys_pages;
    uint32_t _page_count;

public:
    Memory_table();
    Memory_table(uint32_t, int);
    ~Memory_table();

    //Get virtual address from the corresponding physical address from memory_table.
    void* get_virt_addr(const uint32_t phys_addr) const;

    // This function returns physical address with help of pointer, which is offset from the beginning of the buffer.
    void* get_page(void **pages, const uint32_t addr) const;

    // This function returns offset from the beginning of the buffer using (virtual) address in 'pages' and memory_table.
    uint32_t get_offset(void **pages, const uint32_t addr) const;

    //How many bytes are available for reading in circle buffer?
    uint32_t bytes_available(const uint32_t read_addr, const uint32_t write_addr) const;

    uint32_t get_page_count() const;
};


class Linux::RCInput_RPI : public Linux::RCInput
{ 
public:
    void init();
    void _timer_tick(void);
    RCInput_RPI();
    ~RCInput_RPI();
    
private:

    //Physical adresses of peripherals. Are different on different Raspberries.
    uint32_t dma_base;
    uint32_t clk_base;
    uint32_t pcm_base;

    //registers
    static volatile uint32_t *pcm_reg;
    static volatile uint32_t *clk_reg;
    static volatile uint32_t *dma_reg;

    Memory_table *circle_buffer;
    Memory_table *con_blocks;

    uint64_t curr_tick;
    uint64_t prev_tick;
    uint64_t delta_time;

    uint32_t curr_tick_inc;
    uint32_t curr_pointer;
    uint32_t curr_channel;
    uint32_t counter;

    uint16_t width_s0;
    uint16_t width_s1;

    uint8_t curr_signal;
    uint8_t last_signal;
  
    state_t state;
    
    AP_HAL::DigitalSource *enable_pin; 

    void init_dma_cb(dma_cb_t** cbp, uint32_t mode, uint32_t source, uint32_t dest, uint32_t length, uint32_t stride, uint32_t next_cb);
    void* map_peripheral(uint32_t base, uint32_t len);
    void init_registers();
    void init_ctrl_data();
    void init_PCM();
    void init_DMA();
    void init_buffer();
    static void stop_dma();
    static void termination_handler(int signum);
    void set_sigaction();
    void set_physical_addresses(int version);
    void deinit() override;

};

#endif // __AP_HAL_LINUX_RCINPUT_RPI_H__