adb 連線樹莓派，執行程式控制舵機旋轉。

效果圖

連線舵機

1. 樹莓派5V電源線連線舵機的中間的紅線（不同的舵機正負極連線線可能不一樣，需要正確連線，否則可能燒燬舵機）
2. 樹莓派GND連線舵機棕色的負極
3. 樹莓派 PWM輸出線 連線舵機橙色的線

核心程式碼

在子執行緒中動態改變脈衝

  private Runnable mChangePWMRunnable = new Runnable() {
        @Override
        public void run() {
            // Exit Runnable if the port is already closed
            if (mPwm == null) {
                Log.w(TAG, "Stopping runnable since mPwm is null");
                return;
            }

            // Change the duration of the active PWM pulse, but keep it between the minimum and
            // maximum limits.
            // The direction of the change depends on the mIsPulseIncreasing variable, so the pulse
            // will bounce from MIN to MAX.
            if (mIsPulseIncreasing) {
                mActivePulseDuration += PULSE_CHANGE_PER_STEP_MS;
            } else {
                mActivePulseDuration -= PULSE_CHANGE_PER_STEP_MS;
            }

            // Bounce mActivePulseDuration back from the limits
            if (mActivePulseDuration > MAX_ACTIVE_PULSE_DURATION_MS) {
                mActivePulseDuration = MAX_ACTIVE_PULSE_DURATION_MS;
                mIsPulseIncreasing = !mIsPulseIncreasing;
            } else if (mActivePulseDuration < MIN_ACTIVE_PULSE_DURATION_MS) {
                mActivePulseDuration = MIN_ACTIVE_PULSE_DURATION_MS;
                mIsPulseIncreasing = !mIsPulseIncreasing;
            }

            Log.d(TAG, "Changing PWM active pulse duration to " + mActivePulseDuration + " ms");

            try {

                // Duty cycle is the percentage of active (on) pulse over the total duration of the
                // PWM pulse
                mPwm.setPwmDutyCycle(100 * mActivePulseDuration / PULSE_PERIOD_MS);

                // Reschedule the same runnable in {@link #INTERVAL_BETWEEN_STEPS_MS} milliseconds
                mHandler.postDelayed(this, INTERVAL_BETWEEN_STEPS_MS);
            } catch (IOException e) {
                Log.e(TAG, "Error on PeripheralIO API", e);
            }
        }
    };
 

獲取連線PWM的引腳埠，不同裝置對應的埠名稱不一樣注意區分

public class BoardDefaults {
    private static final String DEVICE_RPI3 = "rpi3";
    private static final String DEVICE_IMX6UL_PICO = "imx6ul_pico";
    private static final String DEVICE_IMX7D_PICO = "imx7d_pico";

    /**
     * Return the preferred PWM port for each board.
     */
    public static String getPWMPort() {
        switch (Build.DEVICE) {
            case DEVICE_RPI3:
                return "PWM0";
            case DEVICE_IMX6UL_PICO:
                return "PWM7";
            case DEVICE_IMX7D_PICO:
                return "PWM1";
            default:
                throw new IllegalStateException("Unknown Build.DEVICE " + Build.DEVICE);
        }
    }
}

 

初始化設定並開啟子執行緒

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "Starting PwmActivity");

        try {
            String pinName = BoardDefaults.getPWMPort();
            mActivePulseDuration = MIN_ACTIVE_PULSE_DURATION_MS;

            mPwm = PeripheralManager.getInstance().openPwm(pinName);

            // Always set frequency and initial duty cycle before enabling PWM
            mPwm.setPwmFrequencyHz(1000 / PULSE_PERIOD_MS);
            mPwm.setPwmDutyCycle(mActivePulseDuration);
            mPwm.setEnabled(true);

            // Post a Runnable that continuously change PWM pulse width, effectively changing the
            // servo position
            Log.d(TAG, "Start changing PWM pulse");
            mHandler.post(mChangePWMRunnable);
        } catch (IOException e) {
            Log.e(TAG, "Error on PeripheralIO API", e);
        }
    }