MEMS之重力加速计mma7660与陀螺仪及其样例驱动

原文地址::http://bbs.eeworld.com.cn/thread-244988-1-8.html

 

MEMS之重力加速计mma7660与陀螺仪及其样例驱动

 

 这两天调好了3轴g-sensor ,mma7660, 可以用了. 倾斜晃动或改变板子的方向, mma7660就会产生中断, 并给出当前板子的姿态(水平/垂直, 上下,左右等).

      1. 重力加速度计 mma7660 
      1.1 作用:
            mma7660只是一个3轴g-sensor, 它主要用于测量倾斜角,惯性力,冲击力及震动.

      1.2 工作原理:
          mma7660是一种电容式g-sensor. 电容式g-sensor大多为欧美厂商, 其技术是在wafer的表面做出梳状结构, 当产生动作时,由侦测电容差来判断变形量, 反推出加速度的值.
        与压阻式不同的是, 电容式很难在同一个结构中同时感测到三个轴(X,Y,Z)的变化, 通常都是X,Y和Z分开来的, (这也就是为什么当板子水平放置时,无论如何改变X,Y的位置,都不会有中断产生,因为这时它只能检测Z轴的变化,X,Y的变化它检测不到, 只有当我们将板子倾斜一个角度后才能检测X,Y的变化) . 而压阻式在同一个结构就能感测到三个轴的变化.

       1.3 工作模式:
         mma7660主要有三种工作模式.(通过设置MODE寄存器) 
         1).  Standby(待机)模式
               此时只有I2C工作,接收主机来的指令. 该模式用来设置寄存器. 也就是说, 要想改变mma7660的任何一个寄存器的值,必须先进入Standby模式. 设置完成后再进入Active或Auto-Sleep模式.

         2). Active and Auto-Sleep (活动并且Auto-Sleep) 模式 
               mma7660的工作状态分两种, 一种是高频度采样, 一种是低频度采样. 为什么这样分呢, 为了节省功耗,但是在活动时又保持足够的灵敏度.
               所以说mma7660的Active模式其实又分两种模式,一种是纯粹的Active模式, 即进了Active模式后一直保持高的采样频率,不变. 还有一种是Active & Auto-Sleep模式, 就是说系统激活后先进入高频率采样,经过一定时间后,如果没检测到有活动,它就进入低频率采样 ,所以就叫做Auto-Sleep, Sleep并不是真的Sleep , 只是说降低采样频率.
低频率采样模式又叫Auto-Wake摸式, 即自动唤醒模式.它不是睡眠模式, 它只是降低采样频率.
 
         3). Auto-Wake (自动唤醒) 模式 
              Auto-Sleep后就进入低频率采样模式,这种模式就叫做Auto-Wake摸式, 即自动唤醒模式.它不是睡眠模式, 它只是降低采样频率.

           1.4 初始化:
                                     Init 
                                       | 
                                       |   MODE=(0)
                                进入  Standby 模式,设置寄存器
                                      |
                                      | SRST=0x03,  SR=(2,2,1),  INTSU中,asint=1,plint=1,fbint=1
                                      | MODE=(0, 1, 0, 1, 1, 0, 1)
                                      |
                      Active & Auto-Sleep   (64 Samples/Sec)   
                        ^                                             |
                        | state changes                   |  SPCNT=0xA0 timeout
                        | interrupt                              |
                        |                                              v
                   Auto-Wake ( = Half Sleep)  (8 Samples/Sec)
              

           2. 陀螺仪

               用过g-sensor后就很好奇它跟陀螺仪的关系.               

               在动作感应方面, 加速度计对有变化量的动作感应还不错, 但是对均匀的动作变化, 精度就不够了,陀螺仪则刚好弥补了这一点. 
              陀螺仪的原理是, 对一个旋转的物体, 旋转轴所指的方向在不受外力影响时, 是不会改变的. 人们根据这个原理,用它来保持方向.  陀螺仪在工作时要给它一个力, 使它快速旋转起来, 然后用多种方法读取轴所指的方向,并自动将数据信号传给系统.
              物体在高速旋转后,其轴心就存在指向的稳定性.
              陀螺仪是一种在立体空间内,全方位的角度偏移检测仪器.

           2.1 模型直升机上陀螺仪的功用

              直升机飞行的基本原理是利用主旋翼可变角度产生反向推力而上升, 但对机身会产生扭力作用, 于是需要加设一个尾旋翼来抵消扭力,平横机身. 但怎样使尾旋翼利用合适的角度来平衡机身呢? 这就用到陀螺仪了, 它可以根据机身的摆动多少,自动作出补偿讯号给伺服器,去改变尾旋翼的角度,产生推力平衡机身.以前,模型直升机是没有陀螺仪的, 油门, 主旋翼角度很难配合, 起动后便尽快往上空飞(因为飞行时较易控制),如要悬停就要控制杆快速灵敏的动作,所以很容易撞毁,现在已有多种直升机模型使用的陀螺仪,分别有机械式,电子式,电子自动锁定式.

          2.2  智能手机上陀螺仪的使用

              关注IPHONE4的都知道,它的超强卖点就是内置了陀螺仪, 既有陀螺仪,又有重力加速计. 陀螺仪的主要用途有:
         1).导航.  陀螺仪自被发明以来, 就用于导航, 如果配合GPS, 手机的导航能力将达到前所未有的水准(电子惯导, 但是不能长时间没有GPS校正, 否则会随时间出现偏差). 事实上, 目前很多专业手持式GPS也装了陀螺仪, 如果手机上安装了相应的软件, 其导航能力不亚于目前很多船舶,飞机上的导航仪.
         2).摄像防抖. 配合手机上的摄像头
         3).各类游戏的传感器. 陀螺仪完整检测游戏者手的移动,从而实现个种游戏操作的效果.
         4).可以用作输入设备, 陀螺仪相当于一个立体的鼠标.

         对于安装了陀螺仪,摄像头,以及各种传感器的手机来说,它已经由通讯工具转为娱乐中心,再提升为高效率的生产工具.

//===============================================================样例驱动====================================================

/*
* mma7660.c - Linux kernel modules for 3-Axis Orientation/Motion
* Detection Sensor
*
* Copyright (C) 2009-2010 Freescale Semiconductor Ltd.
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <linux/module.h>

#include <linux/init.h>

#include <linux/slab.h>

#include <linux/i2c.h>

#include <linux/mutex.h>

#include <linux/delay.h>

#include <linux/interrupt.h>

#include <linux/irq.h>

#include <linux/hwmon-sysfs.h>

#include <linux/err.h>

#include <linux/hwmon.h>

#include <linux/fsl_devices.h>

 

/*
* Defines
*/

#if 1
#define assert(expr)\
if(!(expr)) {\
printk( "Assertion failed! %s,%d,%s,%s\n",\
__FILE__,__LINE__,__func__,#expr);\
}
#else
#define assert(expr) do{} while(0)
#endif

#define MMA7660_DRV_NAME "mma7660"
#define MMA7660_XOUT 0x00
#define MMA7660_YOUT 0x01
#define MMA7660_ZOUT 0x02
#define MMA7660_TILT 0x03
#define MMA7660_SRST 0x04
#define MMA7660_SPCNT 0x05
#define MMA7660_INTSU 0x06
#define MMA7660_MODE 0x07
#define MMA7660_SR 0x08
#define MMA7660_PDET 0x09
#define MMA7660_PD 0x0A

#define MK_MMA7660_SR(FILT, AWSR, AMSR)\
(FILT<<5 | AWSR<<3 | AMSR)

#define MK_MMA7660_MODE(IAH, IPP, SCPS, ASE, AWE, TON, MODE)\
(IAH<<7 | IPP<<6 | SCPS<<5 | ASE<<4 | AWE<<3 | TON<<2 | MODE)

#define MK_MMA7660_INTSU(SHINTX, SHINTY, SHINTZ, GINT, ASINT, PDINT, PLINT, FBINT)\
(SHINTX<<7 | SHINTY<<6 | SHINTZ<<5 | GINT<<4 | ASINT<<3 | PDINT<<2 | PLINT<<1 | FBINT)

#define MODE_CHANGE_DELAY_MS 100

ssize_t show_orientation(struct device *dev, struct attribute *attr, char *buf);
ssize_t show_axis_force(struct device *dev, struct attribute *attr, char *buf);
ssize_t show_xyz_force(struct device *dev, struct attribute *attr, char *buf);

static struct device *hwmon_dev;
static int test_test_mode = 0;
static struct i2c_client *mma7660_i2c_client=NULL;
static struct mxc_mma7660_platform_data* plat_data; //Lynn
static u8 orientation;

static SENSOR_DEVICE_ATTR(all_axis_force, S_IRUGO, show_xyz_force, NULL, 0); //defined in linux/include/linux/hwmon-sysfs.h, line 34
static SENSOR_DEVICE_ATTR(x_axis_force, S_IRUGO, show_axis_force, NULL, 0);
static SENSOR_DEVICE_ATTR(y_axis_force, S_IRUGO, show_axis_force, NULL, 1);
static SENSOR_DEVICE_ATTR(z_axis_force, S_IRUGO, show_axis_force, NULL, 2);
static SENSOR_DEVICE_ATTR(orientation, S_IRUGO, show_orientation, NULL, 0);

static struct attribute* mma7660_attrs[] =
{
&sensor_dev_attr_all_axis_force.dev_attr.attr,
&sensor_dev_attr_x_axis_force.dev_attr.attr,
&sensor_dev_attr_y_axis_force.dev_attr.attr,
&sensor_dev_attr_z_axis_force.dev_attr.attr,
&sensor_dev_attr_orientation.dev_attr.attr,
NULL
};

static const struct attribute_group mma7660_group =
{
.attrs = mma7660_attrs,
};

static void mma7660_read_xyz(int idx, s8 *pf)
{
s32 result;

assert(mma7660_i2c_client);
do
{
result=i2c_smbus_read_byte_data(mma7660_i2c_client, idx+MMA7660_XOUT);
assert(result>=0);
}while(result&(1<<6)); //read again if alert
*pf = (result&(1<<5)) ? (result|(~0x0000003f)) : (result&0x0000003f);
printk("dbg:mma7660_read_xyz()/*pf=0x%x\n",*pf);
}

static void mma7660_read_tilt(u8* pt)
{
u32 result;

assert(mma7660_i2c_client);
do
{ 
result = i2c_smbus_read_byte_data(mma7660_i2c_client, MMA7660_TILT);
assert(result>0);
}while(result&(1<<6)); //read again if alert
*pt = result & 0x000000ff;
}

static int print_orientation(int orient,char *buf)
{
int result =0 ;
char buf1[10],buf2[10];

switch((orient>>2)&0x07)
{
case 1:
//result = sprintf(buf, "Left\n");
result = sprintf(buf1, "Left");
break;

case 2:
//result = sprintf(buf, "Right\n");
result = sprintf(buf1, "Right");
break;

case 5:
//result = sprintf(buf, "Downward\n");
result = sprintf(buf1, "Downward");
break;

case 6:
//result = sprintf(buf, "Upward\n");
result = sprintf(buf1, "Upward");
break;
default:
result = sprintf(buf1, "Unknown");

}

switch(orient & 0x03)
{
case 1:
//result = sprintf(buf, "Front\n");
result = sprintf(buf2, "Front");
break;

case 2:
//result = sprintf(buf, "Back\n");
result = sprintf(buf2, "Back");
break;

default:
//result = sprintf(buf, "Unknown\n");
result = sprintf(buf2, "Unknown");
}

result=sprintf(buf,"%s,%s",buf1,buf2);

return result;
}
ssize_t show_orientation(struct device *dev, struct attribute *attr, char *buf)
{
int result;

result = print_orientation(orientation,buf);

return result;
}

ssize_t show_xyz_force(struct device *dev, struct attribute *attr, char *buf)
{
int i;
s8 xyz[3];

for(i=0; i<3; i++)
mma7660_read_xyz(i, &xyz);
printk("dbg:show_xyz_force()/(xyz[0]=%d,xyz[1]=%d,xyz[2]=%d)\n", xyz[0], xyz[1], xyz[2]);
return sprintf(buf, "(%d,%d,%d)\n", xyz[0], xyz[1], xyz[2]);
}

ssize_t show_axis_force(struct device *dev, struct attribute *attr, char *buf)
{
s8 force;
int n = to_sensor_dev_attr(attr)->index;

mma7660_read_xyz(n, &force);
printk("dbg:show_axis_force()/force=%d\n", force);

return sprintf(buf, "%d\n", force);
}

static void mma7660_worker(struct work_struct *work)
{
u8 tilt, new_orientation;
char buf1[20],buf2[20];
int result=0;

mma7660_read_tilt(&tilt);
new_orientation = tilt & 0x1f;
if(orientation!=new_orientation){
//printk("dbg:/mma7660_worker(),orientation=%d,new_orientation=%d\n",orientation,new_orientation);
print_orientation(orientation,buf1);
print_orientation(new_orientation,buf2);
printk("dbg:/mma7660_worker(),orientation changes from %s to %s\n",buf1,buf2);
orientation = new_orientation;

//enter Active + Auto-Wake mode again
if(mma7660_i2c_client)
{
result = i2c_smbus_write_byte_data(mma7660_i2c_client,
MMA7660_MODE, MK_MMA7660_MODE(0, 0, 0, 0, 0, 0, 0)); //enter standby
assert(result==0);

result = i2c_smbus_write_byte_data(mma7660_i2c_client,
//MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 0, 0, 0, 1));
MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 1, 1, 0, 1)); //IPP=1,ASE=1,AWE=1,MODE=1
assert(result==0);
}
}
else
printk("dbg:/mma7660_worker(),exit Auto-Sleep mode to Auto-Wake mode\n");
}

DECLARE_WORK(mma7660_work, mma7660_worker);

// interrupt handler
static irqreturn_t mmx7660_irq_handler(int irq, void *dev_id)
{
schedule_work(&mma7660_work);
//printk("dbg:/mmx7660_irq_handler(irq=%d,dev_id=%s)\n",irq,(char*)dev_id);
return IRQ_RETVAL(1);
}

/*
* Initialization function
*/

static int mma7660_init_client(struct i2c_client *client)
{
int result;

mma7660_i2c_client = client;
plat_data = (struct mxc_mma7660_platform_data *)client->dev.platform_data;
assert(plat_data);

if(test_test_mode)
{
/*
* Probe the device. We try to set the device to Test Mode and then to
* write & verify XYZ registers
*/
result = i2c_smbus_write_byte_data(client, MMA7660_MODE,MK_MMA7660_MODE(0, 0, 0, 0, 0, 1, 0));
assert(result==0);
mdelay(MODE_CHANGE_DELAY_MS);

result = i2c_smbus_write_byte_data(client, MMA7660_XOUT, 0x2a);
assert(result==0);

result = i2c_smbus_write_byte_data(client, MMA7660_YOUT, 0x15);
assert(result==0);

result = i2c_smbus_write_byte_data(client, MMA7660_ZOUT, 0x3f);
assert(result==0);

result = i2c_smbus_read_byte_data(client, MMA7660_XOUT);

result= i2c_smbus_read_byte_data(client, MMA7660_YOUT);

result= i2c_smbus_read_byte_data(client, MMA7660_ZOUT);
assert(result=0x3f);
}

// Enable Orientation Detection Logic
result = i2c_smbus_write_byte_data(client,
MMA7660_MODE, MK_MMA7660_MODE(0, 0, 0, 0, 0, 0, 0)); //enter standby
//printk("result=i2c_smbus_write_byte_data(client, MMA7660_MODE, MK_MMA7660_MODE(0, 0, 0, 0, 0, 0, 0))=%d\n",result);
assert(result==0);

result = i2c_smbus_write_byte_data(client, MMA7660_SRST, 0x03); //AWSRS=1,AMSRS=1

result = i2c_smbus_write_byte_data(client,
MMA7660_SR, MK_MMA7660_SR(2, 2, 1)); //REG = 0x08,sample rate reg,
//MMA7660_SR, MK_MMA7660_SR(2, 2, 2)); //REG = 0x08,sample rate reg,
//FILT = 2, 3 measurement samples at the rate set by AMSR[2:0] or AWSR[1:0]
// have to match before the device updates portrait/landscape data
// in TILT(0x03) register. 
//AWSR = 2, 8 Samples/Second Auto-Wake Mode
//AMSR = 1, 64 Samples/Second Active and Auto-Sleep Mode
//AMSR = 2, 32 Samples/Second Active and Auto-Sleep Mode
//printk("result=i2c_smbus_write_byte_data(client, MMA7660_SR, MK_MMA7660_SR(2, 2, 1));= %d\n",result);
assert(result==0);

result = i2c_smbus_write_byte_data(client,
MMA7660_INTSU, MK_MMA7660_INTSU(0, 0, 0, 0, 1, 0, 1, 1));
//MMA7660_INTSU, MK_MMA7660_INTSU(1, 1, 1, 1, 1, 1, 1, 1));
// ASINT =1 , Exiting Auto-Sleep causes an interrupt
// PLINT =1 , Up/Down/Right/Left position change causes an interrupt
// FBINT =1 , Front/Back position change causes an interrupt
//printk("result=i2c_smbus_write_byte_data(client, MMA7660_INTSU, MK_MMA7660_INTSU(0, 0, 0, 0, 1, 0, 1, 1));= %d\n",result);
assert(result==0);

result = i2c_smbus_write_byte_data(client,
MMA7660_SPCNT, 0xA0);
//printk("result=i2c_smbus_write_byte_data(client, MMA7660_SPCNT, 0xA0); = %d\n",result);
assert(result==0);

result = i2c_smbus_write_byte_data(client,
//MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 0, 0, 0, 1));
MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 1, 1, 0, 1)); //IPP=1,ASE=1,AWE=1,MODE=1
//printk("result=i2c_smbus_write_byte_data(client, MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 0, 0, 0, 1)); = %d\n",result);
assert(result==0);

// MMA7660's INT is connected to imx51 EVK's GPIO4_17
// We install interrupt handler here

printk("plat_data->irq=%d\n",plat_data->irq);
assert(plat_data->irq);
result = request_irq(plat_data->irq, mmx7660_irq_handler,
IRQF_TRIGGER_FALLING , MMA7660_DRV_NAME, NULL);
assert(result==0);

mdelay(MODE_CHANGE_DELAY_MS);

{
u8 tilt; char buf1[20];
mma7660_read_tilt(&tilt);
orientation = tilt&0x1f;
print_orientation(orientation,buf1);
printk("dbg:/mma7660_init_client(),init state %s\n",buf1);
}
return result;
}

static struct input_polled_dev *mma7660_idev;
#define POLL_INTERVAL 100
#define INPUT_FUZZ 4
#define INPUT_FLAT 4
#include 
static void report_abs(void)
{
int i;
s8 xyz[3];
s16 x, y, z;

for(i=0; i<3; i++)
mma7660_read_xyz(i, &xyz);

/* convert signed 10bits to signed 16bits */
x = (short)(xyz[0] << 6) >> 6;
y = (short)(xyz[1] << 6) >> 6;
z = (short)(xyz[2] << 6) >> 6;

input_report_abs(mma7660_idev->input, ABS_X, x);
input_report_abs(mma7660_idev->input, ABS_Y, y);
input_report_abs(mma7660_idev->input, ABS_Z, z);
input_sync(mma7660_idev->input);
printk("dbg:report_abs()/x=%d,y=%d,z=%d\n",x,y,z);
}

static void mma7660_dev_poll(struct input_polled_dev *dev)
{
report_abs();
}
/////////////////////////end//////

/*
* I2C init/probing/exit functions
*/

static int __devinit mma7660_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
int result;
struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);

struct input_dev *idev;

result = i2c_check_functionality(adapter,
I2C_FUNC_SMBUS_BYTE|I2C_FUNC_SMBUS_BYTE_DATA);
assert(result);

/* Initialize the MMA7660 chip */
result = mma7660_init_client(client);
assert(result==0);

result = sysfs_create_group(&client->dev.kobj, &mma7660_group);
assert(result==0);

hwmon_dev = hwmon_device_register(&client->dev);
assert(!(IS_ERR(hwmon_dev)));

dev_info(&client->dev, "build time %s %s\n", __DATE__, __TIME__);

/*input poll device register */
mma7660_idev = input_allocate_polled_device();
if (!mma7660_idev) {
dev_err(&client->dev, "alloc poll device failed!\n");
result = -ENOMEM;
return result;
}
mma7660_idev->poll = mma7660_dev_poll;
mma7660_idev->poll_interval = POLL_INTERVAL;
idev = mma7660_idev->input;
idev->name = MMA7660_DRV_NAME;
idev->id.bustype = BUS_I2C;
idev->dev.parent = &client->dev;
idev->evbit[0] = BIT_MASK(EV_ABS);

//set absolute coordinate maximum range (-512,512) ?
input_set_abs_params(idev, ABS_X, -512, 512, INPUT_FUZZ, INPUT_FLAT);
input_set_abs_params(idev, ABS_Y, -512, 512, INPUT_FUZZ, INPUT_FLAT);
input_set_abs_params(idev, ABS_Z, -512, 512, INPUT_FUZZ, INPUT_FLAT);
result = input_register_polled_device(mma7660_idev);
if (result) {
dev_err(&client->dev, "register poll device failed!\n");
return result;
}
//Caller should also setup pull method and setup capabilities(id,name,phys,bits) of the
//corresponing input_dev structure

//////////////////////////////

return result;
}

static int __devexit mma7660_remove(struct i2c_client *client)
{
int result;

result = i2c_smbus_write_byte_data(client,MMA7660_MODE, MK_MMA7660_MODE(0, 0, 0, 0, 0, 0, 0));
assert(result==0);

free_irq(plat_data->irq, NULL);
sysfs_remove_group(&client->dev.kobj, &mma7660_group);
hwmon_device_unregister(hwmon_dev);

return result;
}

#ifdef CONFIG_PM

static int mma7660_suspend(struct i2c_client *client, pm_message_t mesg)
{
int result;
result = i2c_smbus_write_byte_data(client,
MMA7660_MODE, MK_MMA7660_MODE(0, 0, 0, 0, 0, 0, 0));
assert(result==0);
return result;
}

static int mma7660_resume(struct i2c_client *client)
{
int result;
result = i2c_smbus_write_byte_data(client,
MMA7660_MODE, MK_MMA7660_MODE(0, 1, 0, 0, 0, 0, 1));
assert(result==0);
return result;
}

#else

#define mma7660_suspend NULL
#define mma7660_resume NULL

#endif /* CONFIG_PM */

static const struct i2c_device_id mma7660_id[] = {
{ MMA7660_DRV_NAME, 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, mma7660_id);

static struct i2c_driver mma7660_driver = {
.driver = {
.name = MMA7660_DRV_NAME,
.owner = THIS_MODULE,
},
.suspend = mma7660_suspend,
.resume = mma7660_resume,
.probe = mma7660_probe,
.remove = __devexit_p(mma7660_remove),
.id_table = mma7660_id,
};

static int __init mma7660_init(void)
{
return i2c_add_driver(&mma7660_driver);
}

static void __exit mma7660_exit(void)
{
i2c_del_driver(&mma7660_driver);
}

MODULE_DESCRIPTION("MMA7660 3-Axis Orientation/Motion Detection Sensor driver");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.1");

module_init(mma7660_init);
module_exit(mma7660_exit);