九轴陀螺仪--读接口数据

Posted 2021-02-13 onekey

1.使用i2c链接到树莓派的scl , sda 接口vcc给3v引脚，gnd接树莓派gnd就ok。  

2.要操作mpu必须使用mpu的寄存器实现对参数的设定以及读取，取官方下载资料看了一下，在github上找了一个python代码，运行不了bug太多了，然后精简了一下。终于能读出数据了，读出来的数据都是6个字节的，后来发现这哥们用python 读取mpu没有做字节合并，重写了一下，后来发现数据都是整数，不管我怎么旋转数字都是正的，看了网上的一片文章说寄存器度出来的是一个无符号整数。后来想了半天，用手机下了一个陀螺仪app发现会出现负数的情况，只要向相对轴相反方向做运动就会出现负数，于是想了ctypes,强制转换成int这回数据看起来是有正数和负数了，不过在陀螺仪平放着的时候读书优点太大了都达到3000以上了，明显不是，貌似是这个数字需要转换一下才能使用，我找了N多的资料，终于找到有个人mpu6050的代码里，有一个固定的常亮，他使用acc_x乘以这个固定的常数，然后我测试了一下，确实可行，只要将加速计的值乘以16.4就可以得到正确的值！

 陀螺仪读数要乘以13.我搜索了半天也没有找到为什么要乘以16.4 ，不找了，如果有人看到这篇文章知道为啥乘以16.4请留言，谢谢

使用如下代码需要安装smbus库，在树莓派直接 sudo apt-get install py-smbus就ok了

3.python代码如下：

import smbus
import sched, time
import binascii
from threading import Timer, Thread, Event
from struct import *
import ctypes
from math import acos

import sched, time
import binascii
from struct import *

i2c = smbus.SMBus(1)
addr = 0x68
t0 = time.time()


# ====== initial zone ======
try:
    device_id = i2c.read_byte_data(addr, 0x75)
    print ("Device ID:" + str(hex(device_id)))
    print ("MPU9250 I2C Connected.")
    print("")
except:
    print ("Connect failed")
    print ("")
i2c.write_byte_data(0x68, 0x6a, 0x00)
time.sleep(0.05);
i2c.write_byte_data(0x68, 0x37, 0x02)
i2c.write_byte_data(0x0c, 0x0a, 0x16)

# set frequence for accelerator
i2c.write_byte_data(0x68, 29, 9)


# enable fifo and dmp
# i2c.write_byte_data(0x68 , 106 , 32+64);

# ====== intial done ======



def mpu9250_data_get_and_write():
    # global t_a_g

    # keep AKM pointer on continue measuring
    i2c.write_byte_data(0x0c, 0x0a, 0x16)
    # get MPU9250 smbus block data
    # xyz_g_offset = i2c.read_i2c_block_data(addr, 0x13, 6)
    xyz_a_out = i2c.read_i2c_block_data(addr, 0x3B, 6)
    print("xyz_a_out" + str(list2word(xyz_a_out, calc_accelerator_value)))
    # print("xyz_a_out_org#:"+str(xyz_a_out))

    xyz_g_out = i2c.read_i2c_block_data(addr, 0x43, 6)
    print("xyz_g_out" + str(list2word(xyz_g_out, calc_gyro_value)))
    # xyz_a_offset = i2c.read_i2c_block_data(addr, 0x77, 6)

    # get AK8963 smb#us data (by pass-through way)
    xyz_mag = i2c.read_i2c_block_data(0x0c, 0x03, 6)
    # print("xyz_mag"+str(list2word(xyz_mag)))
    xyz_mag_adj = i2c.read_i2c_block_data(0x0c, 0x10, 3)


def list2word(data_list=[], callback=‘‘):
    data = data_list[:]
    if not len(data):
        return [];

    result = []
    for i in range(3):
        high_byte = data.pop(0)
        low_byte = data.pop(0)
        result.append(callback(float(ctypes.c_int16(((high_byte << 8) | low_byte)).value)))

    return result


def calc_accelerator_value(value):
    return round(value / 16.4)


def calc_gyro_value(value):
    return round(value / 131)


def clear_i2c_and_close_file():
    i2c.write_byte_data(addr, 0x6A, 0x07)


# solution 1: while true
def while_true_method():
    # max_count = raw_input("Enter how many count you want.")
    max_count = 100;
    if max_count < 1: max_count = 1000
    print ("Data Counts: " + str(max_count))

    max_count = int(max_count)
    count = 1

    print ("")
    print ("MPU9250 9axis DATA Recording...")
    while True:
        # if count <= max_count:
        mpu9250_data_get_and_write()
        count += 1
        time.sleep(0.5)
        # else:
        pass
    # break;


while_true_method();