ardupilot/libraries/AP_HAL/Device.h

/*
 * Copyright (C) 2015-2016  Intel Corporation. All rights reserved.
 *
 * This file is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#pragma once

#include <inttypes.h>

#include "AP_HAL_Namespace.h"
#include "utility/functor.h"

/*
 * This is an interface abstracting I2C and SPI devices
 */
class AP_HAL::Device {
public:
    enum BusType {
        BUS_TYPE_UNKNOWN = 0,
        BUS_TYPE_I2C     = 1,
        BUS_TYPE_SPI     = 2,
        BUS_TYPE_UAVCAN  = 3
    };

    enum Speed {
        SPEED_HIGH,
        SPEED_LOW,
    };

    FUNCTOR_TYPEDEF(PeriodicCb, bool);
    typedef void* PeriodicHandle;

    Device(enum BusType type)
    {
        _bus_id.devid_s.bus_type = type;
    }

    // return bus type
    enum BusType bus_type(void) const {
        return _bus_id.devid_s.bus_type;
    }

    // return 24 bit bus identifier
    uint32_t get_bus_id(void) const {
        return _bus_id.devid;
    }

    // set device type within a device class (eg. AP_COMPASS_TYPE_LSM303D)
    void set_device_type(uint8_t devtype) {
        _bus_id.devid_s.devtype = devtype;
    }
    
    
    virtual ~Device() {
        if (_checked.regs != nullptr) {
            delete[] _checked.regs;
        }
    }

    /*
     * Set the speed of future transfers. Depending on the bus the speed may
     * be shared for all devices on the same bus.
     *
     * Return: true if speed was successfully set or platform doesn't implement
     * it; false otherwise.
     */
    virtual bool set_speed(Speed speed)  = 0;

    /*
     * Core transfer function. This does a single bus transaction which
     * sends send_len bytes and receives recv_len bytes back from the slave.
     *
     * Return: true on a successful transfer, false on failure.
     */
    virtual bool transfer(const uint8_t *send, uint32_t send_len,
                          uint8_t *recv, uint32_t recv_len) = 0;

    /**
     * Wrapper function over #transfer() to read recv_len registers, starting
     * by first_reg, into the array pointed by recv. The read flag passed to
     * #set_read_flag(uint8_t) is ORed with first_reg before performing the
     * transfer.
     *
     * Return: true on a successful transfer, false on failure.
     */
    bool read_registers(uint8_t first_reg, uint8_t *recv, uint32_t recv_len)
    {
        first_reg |= _read_flag;
        return transfer(&first_reg, 1, recv, recv_len);
    }

    /**
     * Wrapper function over #transfer() to write a byte to the register reg.
     * The transfer is done by sending reg and val in that order.
     *
     * Return: true on a successful transfer, false on failure.
     */
    bool write_register(uint8_t reg, uint8_t val, bool checked=false)
    {
        uint8_t buf[2] = { reg, val };
        if (checked) {
            set_checked_register(reg, val);
        }
        return transfer(buf, sizeof(buf), nullptr, 0);
    }

    /**
     * set a value for a checked register
     */
    void set_checked_register(uint8_t reg, uint8_t val);

    /**
     * setup for register value checking
     */
    bool setup_checked_registers(uint8_t num_regs);

    /**
     * check next register value for correctness. Return false if value is incorrect
     * or register checking has not been setup
     */
    bool check_next_register(void);
    
    /**
     * Wrapper function over #transfer() to read a sequence of bytes from
     * device. No value is written, differently from the #read_registers()
     * method and hence doesn't include the read flag set by #set_read_flag()
     */
    bool read(uint8_t *recv, uint32_t recv_len)
    {
        return transfer(nullptr, 0, recv, recv_len);
    }

    /*
     * Get the semaphore for the bus this device is in.  This is intended for
     * drivers to use during initialization phase only.
     */
    virtual AP_HAL::Semaphore *get_semaphore() = 0;

    /*
     * Register a periodic callback for this bus. All callbacks on the
     * same bus are made from the same thread with lock already taken. In
     * other words, the callback is not executed on the main thread (or the
     * thread which registered the callback), but in a separate per-bus
     * thread.
     *
     * After registering the periodic callback, the other functions should not
     * be used anymore from other contexts. If it really needs to be done, the
     * lock must be taken.
     *
     * Return: A handle for this periodic callback. To cancel the callback
     * call #unregister_callback() or return false on the callback.
     */
    virtual PeriodicHandle register_periodic_callback(uint32_t period_usec, PeriodicCb) = 0;

    /*
     * Adjust the time for the periodic callback registered with
     * #register_periodic_callback. Note that the time will be re-calculated
     * from the moment this call is made and expire after @period_usec.
     *
     * Return: true if periodic callback was sucessfully adjusted, false otherwise.
     */
    virtual bool adjust_periodic_callback(PeriodicHandle h, uint32_t period_usec) = 0;

    /*
     * Cancel a periodic callback on this bus.
     *
     * Return: true if callback was successfully unregistered, false
     * otherwise.
     */
    virtual bool unregister_callback(PeriodicHandle h) { return false; }

    /**
     * Some devices connected on the I2C or SPI bus require a bit to be set on
     * the register address in order to perform a read operation. This sets a
     * flag to be used by #read_registers(). The flag's default value is zero.
     */
    void set_read_flag(uint8_t flag)
    {
        _read_flag = flag;
    }


    /**
     * make a bus id given bus type, bus number, bus address and
     * device type This is for use by devices that do not use one of
     * the standard HAL Device types, such as UAVCAN devices
     */
    static uint32_t make_bus_id(enum BusType bus_type, uint8_t bus, uint8_t address, uint8_t devtype) {
        union DeviceId d;
        d.devid_s.bus_type = bus_type;
        d.devid_s.bus = bus;
        d.devid_s.address = address;
        d.devid_s.devtype = devtype;
        return d.devid;
    }

    /**
     * return a new bus ID for the same bus connection but a new device type.
     * This is used for auxillary bus connections
     */
    static uint32_t change_bus_id(uint32_t old_id, uint8_t devtype) {
        union DeviceId d;
        d.devid = old_id;
        d.devid_s.devtype = devtype;
        return d.devid;
    }

    /**
     * return bus ID with a new devtype
     */
    uint32_t get_bus_id_devtype(uint8_t devtype) {
        return change_bus_id(get_bus_id(), devtype);
    }
    
protected:
    uint8_t _read_flag = 0;

    /*
      broken out device elements. The bitfields are used to keep
      the overall value small enough to fit in a float accurately,
      which makes it possible to transport over the MAVLink
      parameter protocol without loss of information.
     */
    struct DeviceStructure {
        enum BusType bus_type : 3;
        uint8_t bus: 5;    // which instance of the bus type
        uint8_t address;   // address on the bus (eg. I2C address)
        uint8_t devtype;   // device class specific device type
    };

    union DeviceId {
        struct DeviceStructure devid_s;
        uint32_t devid;
    };
    
    union DeviceId _bus_id;

    // set device address (eg. i2c bus address or spi CS)
    void set_device_address(uint8_t address) {
        _bus_id.devid_s.address = address;
    }

    // set device bus number
    void set_device_bus(uint8_t bus) {
        _bus_id.devid_s.bus = bus;
    }

private:
    // checked registers
    struct checkreg {
        uint8_t regnum;
        uint8_t value;
    };
    struct {
        uint8_t n_allocated;
        uint8_t n_set;
        uint8_t next;
        struct checkreg *regs;
    } _checked;
};