肌电传感器 SEN0240

传感器购买连接。

传感器相关信息，这个也是。

传感器驱动示例代码：

    /*
    * Copyright 2017, OYMotion Inc.
    * All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    *
    * 1. Redistributions of source code must retain the above copyright
    *    notice, this list of conditions and the following disclaimer.
    *
    * 2. Redistributions in binary form must reproduce the above copyright
    *    notice, this list of conditions and the following disclaimer in
    *    the documentation and/or other materials provided with the
    *    distribution.
    *
    * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
    * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
    * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
    * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
    * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
    * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
    * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
    * DAMAGE.
    *
    */

    #if defined(ARDUINO) && ARDUINO >= 100
    #include "Arduino.h"
    #else
    #include "WProgram.h"
    #endif

    #include "EMGFilters.h"

    #define TIMING_DEBUG 1

    #define SensorInputPin A0 // input pin number

    EMGFilters myFilter;
    // discrete filters must works with fixed sample frequence
    // our emg filter only support "SAMPLE_FREQ_500HZ" or "SAMPLE_FREQ_1000HZ"
    // other sampleRate inputs will bypass all the EMG_FILTER
    int sampleRate = SAMPLE_FREQ_1000HZ;
    // For countries where power transmission is at 50 Hz
    // For countries where power transmission is at 60 Hz, need to change to
    // "NOTCH_FREQ_60HZ"
    // our emg filter only support 50Hz and 60Hz input
    // other inputs will bypass all the EMG_FILTER
    int humFreq = NOTCH_FREQ_50HZ;

    // Calibration:
    // put on the sensors, and release your muscles;
    // wait a few seconds, and select the max value as the threshold;
    // any value under threshold will be set to zero
    static int Threshold = 0;

    unsigned long timeStamp;
    unsigned long timeBudget;

    void setup() {
        /* add setup code here */
        myFilter.init(sampleRate, humFreq, true, true, true);

        // open serial
        Serial.begin(115200);

        // setup for time cost measure
        // using micros()
        timeBudget = 1e6 / sampleRate;
        // micros will overflow and auto return to zero every 70 minutes
    }

    void loop() {
        /* add main program code here */
        // In order to make sure the ADC sample frequence on arduino,
        // the time cost should be measured each loop
        /*------------start here-------------------*/
        timeStamp = micros();

        int Value = analogRead(SensorInputPin);

        // filter processing
        int DataAfterFilter = myFilter.update(Value);

        int envlope = sq(DataAfterFilter);
        // any value under threshold will be set to zero
        envlope = (envlope > Threshold) ? envlope : 0;

        timeStamp = micros() - timeStamp;
        if (TIMING_DEBUG) {
            // Serial.print("Read Data: "); Serial.println(Value);
            // Serial.print("Filtered Data: ");Serial.println(DataAfterFilter);
            Serial.print("Squared Data: ");
            Serial.println(envlope);
            // Serial.print("Filters cost time: "); Serial.println(timeStamp);
            // the filter cost average around 520 us
        }

        /*------------end here---------------------*/
        // if less than timeBudget, then you still have (timeBudget - timeStamp) to
        // do your work
        delayMicroseconds(500);
        // if more than timeBudget, the sample rate need to reduce to
        // SAMPLE_FREQ_500HZ
    }

驱动代码需要用到 EMGFilters 库，下载地址。

推荐每次使用时都校准一次，因为即使是同一个人，不同位置的肌电信号也是不同的。

校准流程：

• 将样例代码中的 Threshold 变量改成 0，即：static int Threshold = 0;；
• 上传样例代码至 Arduino 控制板中，然后打开 Arduino IDE 的串口监视器，观察打印的数值；
• 放松手臂上的肌肉，观察串口打印的数值。身心平静，让肌肉放松一会，观察串口监视器打印的最大数值，并记录之。如果数值太大，比如 1000 以上，可尝试微调干电极的放置位置；
• 将样例代码中的 Threshold 变量改成刚才记录的最大数值，重新上传样例代码至 Arduino 主控板。

需要注意的是：

• 使用时必须要把笔记本电脑电源断开才能出正确的波形，不然会有噪音；
• 传感器必须「紧贴」皮肤（肌肉处），否则会出现 0-40000 的规律读值。这是 Arduino 模拟输入引脚的信号。就算不接入传感器，引脚也会有读值。而驱动代码会将该读值放大。