三轴陀螺仪MPU3050驱动解析

MPU3050是invensense公司的三轴陀螺仪芯片,三轴陀螺仪最大的作用就是“测量角速度，以判别物体的运动状态，所以也称为运动传感器.

下图是MPU3050的系统框图,芯片有1个中断引脚,可以通过i2c来控制,获取x Gyro，y Gyro，z Gyro

设备驱动中用mpu3050_sensor结构体来描述MPU3050设备对象(对象中包含i2c客户端及输入设备来处理获取的x,y,z轴数据的传递)

struct mpu3050_sensor {	//mpu3050传感器
	struct i2c_client *client;	//i2c客户端
	struct device *dev;	//设备文件
	struct input_dev *idev;	//输入设备
};

用axis_data来描述获取的x Gyro，y Gyro，z Gyro的数值

struct axis_data {	//轴数据
	s16 x;	//x轴
	s16 y;	//y轴
	s16 z;	//z轴
};

首先注册i2c设备

module_i2c_driver(mpu3050_i2c_driver);

static struct i2c_driver mpu3050_i2c_driver = {
	.driver	= {
		.name	= "mpu3050",
		.owner	= THIS_MODULE,
		.pm	= &mpu3050_pm,
		.of_match_table = mpu3050_of_match,
	},
	.probe		= mpu3050_probe,	//i2c probe方法
	.remove		= __devexit_p(mpu3050_remove),
	.id_table	= mpu3050_ids,
};

i2c设备与驱动匹配需要在板级驱动中注册i2c驱动

htc one max板的做法如下

static struct i2c_board_info __initdata mpu3050_GSBI12_boardinfo[] = {
	{
		I2C_BOARD_INFO("mpu3050", 0xD0 >> 1),
		.irq = PM8921_GPIO_IRQ(PM8921_IRQ_BASE, PM_GYRO_INT),
		.platform_data = &mpu3050_data,
	},
};

然后调用

i2c_register_board_info(MSM8064_GSBI2_QUP_I2C_BUS_ID,
				mpu3050_GSBI12_boardinfo,
				ARRAY_SIZE(mpu3050_GSBI12_boardinfo));

注册i2c板级信息

设备匹配后调用mpu3050_probe方法

static int __devinit mpu3050_probe(struct i2c_client *client,const struct i2c_device_id *id)
{
	struct mpu3050_sensor *sensor;	//mpu3050传感器
	struct input_dev *idev;	//输入设备
	int ret;
	int error;

	sensor = kzalloc(sizeof(struct mpu3050_sensor), GFP_KERNEL);	//分配mpu3050数据
	idev = input_allocate_device();	//分配输入设备
	if (!sensor || !idev) {
		dev_err(&client->dev, "failed to allocate driver data\n");
		error = -ENOMEM;
		goto err_free_mem;
	}

	sensor->client = client;	//捆绑i2c客户端
	sensor->dev = &client->dev;	//捆绑设备文件
	sensor->idev = idev;	//捆绑输入设备

	mpu3050_set_power_mode(client, 1);	//设置设备正常电压模式
	msleep(10);	//睡眠
	
	ret = i2c_smbus_read_byte_data(client, MPU3050_CHIP_ID_REG);//获取0x00寄存器值
	if (ret < 0) {
		dev_err(&client->dev, "failed to detect device\n");
		error = -ENXIO;
		goto err_free_mem;
	}

	if (ret != MPU3050_CHIP_ID) {	//判断芯片ID值(0x69)是否MPU3050
		dev_err(&client->dev, "unsupported chip id\n");
		error = -ENXIO;
		goto err_free_mem;
	}

	idev->name = "MPU3050";	//设置输入设备名
	idev->id.bustype = BUS_I2C;	//输入设备使用i2c总线
	idev->dev.parent = &client->dev;	//设置i2c设备为输入设备父设备

	idev->open = mpu3050_input_open;	//输入设备打开方法
	idev->close = mpu3050_input_close;	//输入设备关闭方法

	__set_bit(EV_ABS, idev->evbit);	//设置绝对位移事件标志位,设置各轴数据范围
	input_set_abs_params(idev, ABS_X,MPU3050_MIN_VALUE, MPU3050_MAX_VALUE, 0, 0);
	input_set_abs_params(idev, ABS_Y,MPU3050_MIN_VALUE, MPU3050_MAX_VALUE, 0, 0);
	input_set_abs_params(idev, ABS_Z,MPU3050_MIN_VALUE, MPU3050_MAX_VALUE, 0, 0);

	input_set_drvdata(idev, sensor);	//&idev->dev->p->driver_data=sensor

	pm_runtime_set_active(&client->dev);

	error = mpu3050_hw_init(sensor);	//初始化MPU3050固件
	if (error)
		goto err_pm_set_suspended;
	//申请中断,上升沿触发
	error = request_threaded_irq(client->irq,NULL, mpu3050_interrupt_thread,IRQF_TRIGGER_RISING,"mpu3050", sensor);
	if (error) {
		dev_err(&client->dev,"can't get IRQ %d, error %d\n", client->irq, error);
		goto err_pm_set_suspended;
	}

	error = input_register_device(idev);	//注册输入设备
	if (error) {
		dev_err(&client->dev, "failed to register input device\n");
		goto err_free_irq;
	}

	pm_runtime_enable(&client->dev);
	pm_runtime_set_autosuspend_delay(&client->dev, MPU3050_AUTO_DELAY);

	return 0;

err_free_irq:
	free_irq(client->irq, sensor);
err_pm_set_suspended:
	pm_runtime_set_suspended(&client->dev);
err_free_mem:
	input_free_device(idev);
	kfree(sensor);
	return error;
}

申请,配置,注册相应的input设备,设置电源模式,初始化mpu3050芯片,申请中断,并指明中断返回函数

设置电源模式:mpu3050有两种电压模式val=1为正常模式,val=0为低功耗模式

static void mpu3050_set_power_mode(struct i2c_client *client, u8 val)
{
	u8 value;
	value = i2c_smbus_read_byte_data(client, MPU3050_PWR_MGM);//获取0x3E寄存器数据
	//根据val值设置0x3E寄存器第6位SLEEP
	value = (value & ~MPU3050_PWR_MGM_MASK) |
		(((val << MPU3050_PWR_MGM_POS) & MPU3050_PWR_MGM_MASK) ^ MPU3050_PWR_MGM_MASK);
	i2c_smbus_write_byte_data(client, MPU3050_PWR_MGM,value);//设置0x3E寄存器数据
}

初始化mpu3050：软复位,配置时钟及分频...

static int __devinit mpu3050_hw_init(struct mpu3050_sensor *sensor)
{
	struct i2c_client *client = sensor->client;	//获取i2c客户端
	int ret;
	u8 reg;

	/* Reset 设置0x3E寄存器第7位H_RESET*/
	ret = i2c_smbus_write_byte_data(client, MPU3050_PWR_MGM,MPU3050_PWR_MGM_RESET);
	if (ret < 0)
		return ret;
	//获取0x3E寄存器值
	ret = i2c_smbus_read_byte_data(client, MPU3050_PWR_MGM);
	if (ret < 0)
		return ret;

	ret &= ~MPU3050_PWR_MGM_CLKSEL;	//清除0x3E寄存器0~2位CLK_SET值
	ret |= MPU3050_PWR_MGM_PLL_Z;	//设置0x3E寄存器CLK_SET值为0x03
	ret = i2c_smbus_write_byte_data(client, MPU3050_PWR_MGM,ret);//设置0x3E寄存器
	if (ret < 0)
		return ret;

	/* Output frequency divider. The poll interval 设置0x15寄存器值为119输出分频值*/
	ret = i2c_smbus_write_byte_data(client, MPU3050_SMPLRT_DIV,MPU3050_DEFAULT_POLL_INTERVAL - 1);
	if (ret < 0)
		return ret;

	/* Set low pass filter and full scale 设置低通滤波器和全扫描范围*/
	reg = MPU3050_DEFAULT_FS_RANGE;
	reg |= MPU3050_DLPF_CFG_42HZ << 3;
	reg |= MPU3050_EXT_SYNC_NONE << 5;
	ret = i2c_smbus_write_byte_data(client, MPU3050_DLPF_FS_SYNC, reg);//设置0x16寄存器
	if (ret < 0)
		return ret;

	return 0;
}

中断返回函数:读取xyz轴数值,并上报给input子系统

static irqreturn_t mpu3050_interrupt_thread(int irq, void *data)
{
	struct mpu3050_sensor *sensor = data;	//获取mpu3050传感器
	struct axis_data axis;

	mpu3050_read_xyz(sensor->client, &axis);	//获取xyz轴数值

	input_report_abs(sensor->idev, ABS_X, axis.x);	//上报x轴事件
	input_report_abs(sensor->idev, ABS_Y, axis.y);	//上报y轴事件
	input_report_abs(sensor->idev, ABS_Z, axis.z);	//上报z轴事件
	input_sync(sensor->idev);	//同步事件

	return IRQ_HANDLED;
}

获取xyz轴数值,通过i2c命令去获取便可

static int mpu3050_xyz_read_reg(struct i2c_client *client,u8 *buffer, int length)
{
	/*
	 * Annoying we can't make this const because the i2c layer doesn't
	 * declare input buffers const.
	 */
	char cmd = MPU3050_XOUT_H;	//i2c读取0x1D~0x22寄存器值
	struct i2c_msg msg[] = {
		{
			.addr = client->addr,
			.flags = 0,
			.len = 1,
			.buf = &cmd,
		},
		{
			.addr = client->addr,
			.flags = I2C_M_RD,
			.len = length,
			.buf = buffer,
		},
	};

	return i2c_transfer(client->adapter, msg, 2);
}

应用层在MPU3050设备节点的时候会开启中断,MPU3050有数据更新则会触发中断,接着调用中断返回函数上报事件，应用程序便可读取设备节点获取xyz轴的数据

static int mpu3050_input_open(struct input_dev *input)
{
	struct mpu3050_sensor *sensor = input_get_drvdata(input);	//获取mpu3050传感器
	int error;

	pm_runtime_get(sensor->dev);

	/* Enable interrupts 
	使能中断,设置0x17寄存器MPU_RDY_EN,DMP_DONE_EN,RAW_RDY_EN位*/
	error = i2c_smbus_write_byte_data(sensor->client, MPU3050_INT_CFG,
			MPU3050_LATCH_INT_EN | MPU3050_RAW_RDY_EN | MPU3050_MPU_RDY_EN);
	if (error < 0) {
		pm_runtime_put(sensor->dev);
		return error;
	}

	return 0;
}