最近新發現手裏有三個9G 的舵機和之前想做無人機時買的三軸陀螺儀模塊,閒着沒事在家制作一個手機穩定器。
製作手機穩定器的原理無非是:
三軸陀螺儀檢測到X軸方向沿負方向運動,那麼相機相應X軸的舵機就進行相反的方向移動,以抵消晃動。
我的三軸陀螺儀的芯片是L3G4200D;
在網上有些玩家用的是6軸陀螺儀,MPU6050.相應的庫也很健全,但是目前我沒有,只能充分利用手裏的東西。
電路連線如圖所示:
相應的三維結構圖如下:
採用標準的笛卡爾三維結構,編程也方便,數學模型好建立。
關於L3G4200D陀螺儀,有如下案例:
L3G4200D是意法(ST)半導體公司推出的一款MEMS運動傳感器:三軸數字輸出陀螺儀。可選-250~250、-500~500、-2000-2000dps
開發環境:
系統:XP
單板:Arduino Leonardo
平臺:arduino-1.8.12
目標:讀三軸陀螺儀的原始數據,並通過串口顯示
一、硬件介紹
三軸陀螺儀L3G4200D模塊的原理圖如下:
這裏只用到SCL、SDA、VCC_3.3V、GND分別連接到Arduino的對應接口上。Arduino Leonardo上直接標有SDA、SCL連上即可,其它Arduino根據自己的板子連接。
二、編寫測試代碼
現在的arduino版本高,在網上找的例程都編譯通不過,換了個低版本才編譯通過。可以參考這個上面的代碼 https://github.com/pololu/L3G4200D/tree/66f1448d7f6767e12d0fe0c5c50d4e037aedc27c/L3G4200D 找到這兩個文件L3G4200D.cpp L3G4200D.h,但文件好像不能直接下,代碼都貼在網頁上,直接copy下來。然後還要在arduino-1.0.1-windows\arduino-1.0.1\libraries下新建L3G4200D目錄,將L3G4200D.cpp L3G4200D.h拷到剛建的L3G4200D,就可以在Android中使用L3G4200D類。
文件L3G4200D.cpp
#include <L3G4200D.h>
#include <Wire.h>
#include <math.h>
// Defines ////////////////////////////////////////////////////////////////
// The Arduino two-wire interface uses a 7-bit number for the address,
// and sets the last bit correctly based on reads and writes
#define GYR_ADDRESS (0xD2 >> 1)
// Public Methods //////////////////////////////////////////////////////////////
// Turns on the L3G4200D's gyro and places it in normal mode.
void L3G4200D::enableDefault(void)
{
// 0x0F = 0b00001111
// Normal power mode, all axes enabled
writeReg(L3G4200D_CTRL_REG1, 0x0F);
}
// Writes a gyro register
void L3G4200D::writeReg(byte reg, byte value)
{
Wire.beginTransmission(GYR_ADDRESS);
Wire.write(reg);
Wire.write(value);
Wire.endTransmission();
}
// Reads a gyro register
byte L3G4200D::readReg(byte reg)
{
byte value;
Wire.beginTransmission(GYR_ADDRESS);
Wire.write(reg);
Wire.endTransmission();
Wire.requestFrom(GYR_ADDRESS, 1);
value = Wire.read();
Wire.endTransmission();
return value;
}
// Reads the 3 gyro channels and stores them in vector g
void L3G4200D::read()
{
Wire.beginTransmission(GYR_ADDRESS);
// assert the MSB of the address to get the gyro
// to do slave-transmit subaddress updating.
Wire.write(L3G4200D_OUT_X_L | (1 << 7));
Wire.endTransmission();
Wire.requestFrom(GYR_ADDRESS, 6);
while (Wire.available() < 6);
uint8_t xla = Wire.read();
uint8_t xha = Wire.read();
uint8_t yla = Wire.read();
uint8_t yha = Wire.read();
uint8_t zla = Wire.read();
uint8_t zha = Wire.read();
g.x = xha << 8 | xla;
g.y = yha << 8 | yla;
g.z = zha << 8 | zla;
}
void L3G4200D::vector_cross(const vector *a,const vector *b, vector *out)
{
out->x = a->y*b->z - a->z*b->y;
out->y = a->z*b->x - a->x*b->z;
out->z = a->x*b->y - a->y*b->x;
}
float L3G4200D::vector_dot(const vector *a,const vector *b)
{
return a->x*b->x+a->y*b->y+a->z*b->z;
}
void L3G4200D::vector_normalize(vector *a)
{
float mag = sqrt(vector_dot(a,a));
a->x /= mag;
a->y /= mag;
a->z /= mag;
}
文件L3G4200D.h:
#ifndef L3G4200D_h
#define L3G4200D_h
#include <Arduino.h> // for byte data type
// register addresses
#define L3G4200D_WHO_AM_I 0x0F
#define L3G4200D_CTRL_REG1 0x20
#define L3G4200D_CTRL_REG2 0x21
#define L3G4200D_CTRL_REG3 0x22
#define L3G4200D_CTRL_REG4 0x23
#define L3G4200D_CTRL_REG5 0x24
#define L3G4200D_REFERENCE 0x25
#define L3G4200D_OUT_TEMP 0x26
#define L3G4200D_STATUS_REG 0x27
#define L3G4200D_OUT_X_L 0x28
#define L3G4200D_OUT_X_H 0x29
#define L3G4200D_OUT_Y_L 0x2A
#define L3G4200D_OUT_Y_H 0x2B
#define L3G4200D_OUT_Z_L 0x2C
#define L3G4200D_OUT_Z_H 0x2D
#define L3G4200D_FIFO_CTRL_REG 0x2E
#define L3G4200D_FIFO_SRC_REG 0x2F
#define L3G4200D_INT1_CFG 0x30
#define L3G4200D_INT1_SRC 0x31
#define L3G4200D_INT1_THS_XH 0x32
#define L3G4200D_INT1_THS_XL 0x33
#define L3G4200D_INT1_THS_YH 0x34
#define L3G4200D_INT1_THS_YL 0x35
#define L3G4200D_INT1_THS_ZH 0x36
#define L3G4200D_INT1_THS_ZL 0x37
#define L3G4200D_INT1_DURATION 0x38
class L3G4200D
{
public:
typedef struct vector
{
float x, y, z;
} vector;
vector g; // gyro angular velocity readings
void enableDefault(void);
void writeReg(byte reg, byte value);
byte readReg(byte reg);
void read(void);
// vector functions
static void vector_cross(const vector *a, const vector *b, vector *out);
static float vector_dot(const vector *a,const vector *b);
static void vector_normalize(vector *a);
};
#endif
文件L3G4200D.ino
#include <Wire.h>
#include <L3G4200D.h>
L3G4200D gyro;
void setup() {
Serial.begin(9600);
Wire.begin();
gyro.enableDefault();
}
void loop() {
gyro.read();
Serial.print("G ");
Serial.print("X: ");
Serial.print((int)gyro.g.x);
Serial.print(" Y: ");
Serial.print((int)gyro.g.y);
Serial.print(" Z: ");
Serial.println((int)gyro.g.z);
delay(100);
}
三、編譯測試
Arduino還是很方便操作的,選擇好單板、參考,直接點上面的“對勾”就開始編譯,編譯沒問題,點“->”箭頭狀的,開始上傳程序,直至上傳進度條完成。
接着打開Tools/Serial Monitor 顯示如下:
這是水平放置的結果,傾斜模塊會看到值變化。
最終代碼如下:
/*
DIY Gimbal - MPU6050 Arduino Tutorial
by Dejan, www.HowToMechatronics.com
Code based on the MPU6050_DMP6 example from the i2cdevlib library by Jeff Rowberg:
https://github.com/jrowberg/i2cdevlib
*/
// I2Cdev and MPU6050 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"
#include "MPU6050_6Axis_MotionApps20.h"
//#include "MPU6050.h" // not necessary if using MotionApps include file
// Arduino Wire library is required if I2Cdev I2CDEV_ARDUINO_WIRE implementation
// is used in I2Cdev.h
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif
#include <Servo.h>
// class default I2C address is 0x68
// specific I2C addresses may be passed as a parameter here
// AD0 low = 0x68 (default for SparkFun breakout and InvenSense evaluation board)
// AD0 high = 0x69
MPU6050 mpu;
//MPU6050 mpu(0x69); // <-- use for AD0 high
// Define the 3 servo motors
Servo servo0;
Servo servo1;
Servo servo2;
float correct;
int j = 0;
#define OUTPUT_READABLE_YAWPITCHROLL
#define INTERRUPT_PIN 2 // use pin 2 on Arduino Uno & most boards
bool blinkState = false;
// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer
// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorInt16 aa; // [x, y, z] accel sensor measurements
VectorInt16 aaReal; // [x, y, z] gravity-free accel sensor measurements
VectorInt16 aaWorld; // [x, y, z] world-frame accel sensor measurements
VectorFloat gravity; // [x, y, z] gravity vector
float euler[3]; // [psi, theta, phi] Euler angle container
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector
// packet structure for InvenSense teapot demo
uint8_t teapotPacket[14] = { '$', 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x00, '\r', '\n' };
// ================================================================
// === INTERRUPT DETECTION ROUTINE ===
// ================================================================
volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void dmpDataReady() {
mpuInterrupt = true;
}
// ================================================================
// === INITIAL SETUP ===
// ================================================================
void setup() {
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
Wire.begin();
Wire.setClock(400000); // 400kHz I2C clock. Comment this line if having compilation difficulties
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
Fastwire::setup(400, true);
#endif
// initialize serial communication
// (115200 chosen because it is required for Teapot Demo output, but it's
// really up to you depending on your project)
Serial.begin(38400);
while (!Serial); // wait for Leonardo enumeration, others continue immediately
// initialize device
//Serial.println(F("Initializing I2C devices..."));
mpu.initialize();
pinMode(INTERRUPT_PIN, INPUT);
devStatus = mpu.dmpInitialize();
// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(17);
mpu.setYGyroOffset(-69);
mpu.setZGyroOffset(27);
mpu.setZAccelOffset(1551); // 1688 factory default for my test chip
// make sure it worked (returns 0 if so)
if (devStatus == 0) {
// turn on the DMP, now that it's ready
// Serial.println(F("Enabling DMP..."));
mpu.setDMPEnabled(true);
attachInterrupt(digitalPinToInterrupt(INTERRUPT_PIN), dmpDataReady, RISING);
mpuIntStatus = mpu.getIntStatus();
// set our DMP Ready flag so the main loop() function knows it's okay to use it
//Serial.println(F("DMP ready! Waiting for first interrupt..."));
dmpReady = true;
// get expected DMP packet size for later comparison
packetSize = mpu.dmpGetFIFOPacketSize();
} else {
// ERROR!
// 1 = initial memory load failed
// 2 = DMP configuration updates failed
// (if it's going to break, usually the code will be 1)
// Serial.print(F("DMP Initialization failed (code "));
//Serial.print(devStatus);
//Serial.println(F(")"));
}
// Define the pins to which the 3 servo motors are connected
servo0.attach(10);
servo1.attach(9);
servo2.attach(8);
}
// ================================================================
// === MAIN PROGRAM LOOP ===
// ================================================================
void loop() {
// if programming failed, don't try to do anything
if (!dmpReady) return;
// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize) {
if (mpuInterrupt && fifoCount < packetSize) {
// try to get out of the infinite loop
fifoCount = mpu.getFIFOCount();
}
}
// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();
// get current FIFO count
fifoCount = mpu.getFIFOCount();
// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & _BV(MPU6050_INTERRUPT_FIFO_OFLOW_BIT)) || fifoCount >= 1024) {
// reset so we can continue cleanly
mpu.resetFIFO();
fifoCount = mpu.getFIFOCount();
Serial.println(F("FIFO overflow!"));
// otherwise, check for DMP data ready interrupt (this should happen frequently)
} else if (mpuIntStatus & _BV(MPU6050_INTERRUPT_DMP_INT_BIT)) {
// wait for correct available data length, should be a VERY short wait
while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);
// track FIFO count here in case there is > 1 packet available
// (this lets us immediately read more without waiting for an interrupt)
fifoCount -= packetSize;
// Get Yaw, Pitch and Roll values
#ifdef OUTPUT_READABLE_YAWPITCHROLL
mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
// Yaw, Pitch, Roll values - Radians to degrees
ypr[0] = ypr[0] * 180 / M_PI;
ypr[1] = ypr[1] * 180 / M_PI;
ypr[2] = ypr[2] * 180 / M_PI;
// Skip 300 readings (self-calibration process)
if (j <= 300) {
correct = ypr[0]; // Yaw starts at random value, so we capture last value after 300 readings
j++;
}
// After 300 readings
else {
ypr[0] = ypr[0] - correct; // Set the Yaw to 0 deg - subtract the last random Yaw value from the currrent value to make the Yaw 0 degrees
// Map the values of the MPU6050 sensor from -90 to 90 to values suatable for the servo control from 0 to 180
int servo0Value = map(ypr[0], -90, 90, 0, 180);
int servo1Value = map(ypr[1], -90, 90, 0, 180);
int servo2Value = map(ypr[2], -90, 90, 180, 0);
// Control the servos according to the MPU6050 orientation
servo0.write(servo0Value);
servo1.write(servo1Value);
servo2.write(servo2Value);
}
#endif
}
}