mpu6050.c

/**
 * Copyright (c) 2009 - 2017, Nordic Semiconductor ASA
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 * 
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 * 
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 * 
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 * 
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
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 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 */
#include <stdbool.h>
#include <stdint.h>

#include "twi_master.h"
#include "mpu6050.h"

/*lint ++flb "Enter library region" */

#define ADDRESS_WHO_AM_I          (0x75U) // !< WHO_AM_I register identifies the device. Expected value is 0x68.
#define ADDRESS_SIGNAL_PATH_RESET (0x68U) // !<

static const uint8_t expected_who_am_i = 0x68U; // !< Expected value to get from WHO_AM_I register.
static uint8_t       m_device_address;          // !< Device address in bits [7:1]

bool mpu6050_init(uint8_t device_address)
{
    bool transfer_succeeded = true;

    m_device_address = (uint8_t)(device_address << 1);

    // Do a reset on signal paths
    uint8_t reset_value = 0x04U | 0x02U | 0x01U; // Resets gyro, accelerometer and temperature sensor signal paths.
    transfer_succeeded &= mpu6050_register_write(ADDRESS_SIGNAL_PATH_RESET, reset_value);

    // Read and verify product ID
    transfer_succeeded &= mpu6050_verify_product_id();

    return transfer_succeeded;
}

bool mpu6050_verify_product_id(void)
{
    uint8_t who_am_i;

    if (mpu6050_register_read(ADDRESS_WHO_AM_I, &who_am_i, 1))
    {
        if (who_am_i != expected_who_am_i)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
    else
    {
        return false;
    }
}

bool mpu6050_register_write(uint8_t register_address, uint8_t value)
{
    uint8_t w2_data[2];

    w2_data[0] = register_address;
    w2_data[1] = value;
    return twi_master_transfer(m_device_address, w2_data, 2, TWI_ISSUE_STOP);
}

bool mpu6050_register_read(uint8_t register_address, uint8_t * destination, uint8_t number_of_bytes)
{
    bool transfer_succeeded;
    transfer_succeeded  = twi_master_transfer(m_device_address, &register_address, 1, TWI_DONT_ISSUE_STOP);
    transfer_succeeded &= twi_master_transfer(m_device_address|TWI_READ_BIT, destination, number_of_bytes, TWI_ISSUE_STOP);
    return transfer_succeeded;
}

/*lint --flb "Leave library region" */