1、总体思路
采用esp32s arduino编程，采集adxl335的模拟量数据，可以根据三轴的变化即可计算角度变化；
2、相关配件
esp32s开发板
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esp32s引脚图，标有ad开头的都是可以通讯模拟量数据；
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gy-61 adxl335 提供xyz三轴变化数字；
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3、原理参考
官方理论
https://www.analog.com/media/cn/technical-documentation/application-notes/AN-1057_cn.pdf
理论内容参考
https://www.electronicwings.com/sensors-modules/adxl335-accelerometer-module
https://www.electronicwings.com/arduino/adxl335-accelerometer-interfacing-with-arduino-uno
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<看到数学题瞬间头疼>
esp32 adc相关参考
https://lastminuteengineers.com/adxl335-accelerometer-arduino-tutorial/
https://microcontrollerslab.com/adc-esp32-measuring-voltage-example/
https://microcontrollerslab.com/esp32-pinout-use-gpio-pins/
esp32的adc输出值等于接入电压*输出值除以4095
voltage_value = (ADC_VALUE * 3.3 ) / (4095);
Serial.print("Voltage = ");
Serial.print(voltage_value);
Serial.print("volts");
delay(1000);
3、esp32s 和adxl335接线图
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示意图采用arduino板子。原理一样。
esp32s按照下列接口接起来；
const int x_out = 36;
const int y_out = 39;
const int z_out = 34;
注:VCC要接5V电源，跟算法有关。
采用杜邦线连起来；
4、代码思路
esp32读取模拟量电压值，
计算ADXL335重力偏离值；
再计算便宜角度和旋转角度，算法参考理论说明；
//引入数学计算库
#include <math.h>
//变量定义----------------------------bigen
// x-axis x轴数据 对应gpio36
const int x_out = 36;
// y-axis y轴数据 对应gpio36
const int y_out = 39;
// z-axis z轴数据 对应gpio36
const int z_out = 34;
// 采集10次样本以降低噪音
const int sampleSize = 10;
//变量定义--------------------------------end
//函数定义----------------------------bigen
// 采样获取均值
int ReadAxis(int axisPin)
{
long reading = 0;
// 读取adc值
analogRead(axisPin);
delay(1);
for (int i = 0; i < sampleSize; i++)
{
reading += analogRead(axisPin);
}
// 返回adc平均值
return reading / sampleSize;
}
//初始化串口
void setupSerial() {
// 初始化默认串口
Serial.begin(115200);
// 因为采用默认串口和nb_iot模块通讯，可以另外用软串口输出调试信息；
}
//函数定义--------------------------------end
//主程序----------------------------bigen
void setup() {
// 初始化串口
setupSerial();
delay(1000);
}
void loop() {
//定义x/y/z模拟量值
int ADC_X_VALUE, ADC_Y_VALUE, ADC_Z_VALUE;
// 定义x/y/z重力单元值
double Axout, Ayout, Azout;
//定义倾斜度
double theta, psy, phi;
// 定义偏转度
double roll, pitch, yaw;
Serial.println();
//读取x/y/z轴模拟量数据，等于电压值
ADC_X_VALUE = ReadAxis(x_out);
ADC_Y_VALUE = ReadAxis(y_out);
ADC_Z_VALUE = ReadAxis(z_out);
//计算x/y/z重力单元值，esp32的adc需要以4095参数，0.333来源于adxl说明，大部分采用0.330
Axout = ( ( ( (double)(ADC_X_VALUE * 5) / 4095) - 1.65 ) / 0.333 );
Ayout = ( ( ( (double)(ADC_Y_VALUE * 5) / 4095) - 1.65 ) / 0.333 );
Azout = ( ( ( (double)(ADC_Z_VALUE * 5) / 4095) - 1.65 ) / 0.333 );
Serial.print("Axout = ");
Serial.print(Axout);
Serial.print("\t\t");
Serial.print("Ayout = ");
Serial.print(Ayout);
Serial.print("\t\t");
Serial.print("Azout = ");
Serial.print(Azout);
Serial.print("\t\t");
Serial.println();
//计算偏离角度，公式参考原理说明
theta = atan(Axout / (sqrt((pow (Ayout, 2.0)) + (pow (Azout, 2.0))))) * 57.29577951;
psy = atan(Ayout / (sqrt((pow (Axout, 2.0)) + (pow (Azout, 2.0))))) * 57.29577951;
phi = atan((sqrt((pow (Ayout, 2.0)) + (pow (Axout, 2.0)))) / Azout) * 57.29577951;
Serial.print("theta = ");
Serial.print(theta);
Serial.print("\t\t");
Serial.print("psy = ");
Serial.print(psy);
Serial.print("\t\t");
Serial.print("phi = ");
Serial.print(phi);
Serial.print("\t\t");
Serial.println();
//计算旋转角度，公式参考原理说明
roll = (atan2(Ayout, Azout)) * 57.29577951 + 180;
pitch = (atan2(Azout, Axout)) * 57.29577951 + 180;
yaw = (atan2(Axout, Ayout)) * 57.29577951 + 180;
Serial.print("roll = ");
Serial.print(roll);
Serial.print("\t\t");
Serial.print("pitch = ");
Serial.print(pitch);
Serial.print("\t\t");
Serial.print("pitch = ");
Serial.print(pitch);
Serial.print("\t\t");
Serial.println();
//间隔3秒采集一次
delay(3000);
}
//主程序--------------------------------end
5、查看效果
移动模块数字变化显示；
roll = 211.53 pitch = 211.57 pitch = 211.57
[16:27:06.486]
Axout = 1.44 Ayout = 0.54 Azout = 0.89
theta = 54.25 psy = 17.64 phi = 60.04
roll = 211.25 pitch = 211.61 pitch = 211.61
[16:27:09.487]
[16:27:09.496] Axout = 0.47 Ayout = 1.10 Azout = 2.26
theta = 10.65 psy = 25.40 phi = 27.84
roll = 205.88 pitch = 258.20 pitch = 258.20
[16:27:12.497]
Axout = 0.46 Ayout = 1.03 Azout = 2.23
theta = 10.54 psy = 24.23 phi = 26.70
roll = 204.68 pitch = 258.43 pitch = 258.43
[16:27:15.496]
Axout = 0.49 Ayout = 1.01 Azout = 2.23
theta = 11.40 psy = 23.78 phi = 26.68
roll = 204.29 pitch = 257.53 pitch = 257.53
[16:27:18.495]
[16:27:18.505] Axout = 0.46 Ayout = 1.01 Azout = 2.25
theta = 10.56 psy = 23.80 phi = 26.31
roll = 204.23 pitch = 258.45 pitch = 258.45
[16:27:21.507]
Axout = 1.67 Ayout = 1.21 Azout = 0.43
theta = 52.51 psy = 35.00 phi = 78.25
roll = 250.46 pitch = 194.39 pitch = 194.39
[16:27:24.508]
Axout = 2.23 Ayout = 2.14 Azout = 0.42
theta = 45.65 psy = 43.29 phi = 82.19
roll = 258.79 pitch = 190.76 pitch = 190.76
6、场景应用
理论和实际角度感受值感觉有差异，还未验证测通。
真实的应用场景最好是建立自己的标准库，跟标准库比较做预警。
还需要理论研究。
7、上报思路
文章可参考esp32-cam用nb_iot sim7020上报思路，代码可复用。不赘述。
全文完。
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