player pro control by button

/**
 * @brief Test Connection
 */
AT  //Test Connection

/**
 * @brief Set/Query Volume（Volume：0-30）(Power-down save)
 * @param -n:Volume -n
 *        +n:Volume +n
 *         n:Designate volume to n
 *         ?:Query volume
 */
AT+VOL=-5  //Volume -5

AT+VOL=?   //Query volume
return：VOL = [10]   //The current volume is 10

/**
 * @brief Control playback mode
 * @param  1:repeat one song
 *         2:repeat all
 *         3:play one song and pause
 *         4:Play randomly
 *         5:Repeat all in the folder
 *         ?:query the current playback mode
 */
AT+PLAYMODE=1   //Switch to repeat-one-song mode

AT+PLAYMODE=?   //Query current playback mode
Return：PLAYMODE =1  //Current playback mode: repeat one song

/**
 * @brief Control playing
 * @param    PP:Play & Pause
 *         NEXT:next
 *         LAST:last
 */
AT+PLAY=NEXT   //last

/**
 * @brief Playing time control
 * @param -n:Fast Rewind n S
 *        +n:Fast Forward n S
 *         n:Start playing from the Nth second
 */
AT+TIME=-5   //Fast Rewind 5S

/**
 * @brief Query playback information
 * @param  1:Query the file number of the currently-playing file
 *         2:Query the total number of the files
 *         3:Query the time length the song has played
 *         4:Query the total time of the currently-playing file
 *         5:Query the file name of the currently-playing file
 */
AT+QUERY=1   //Query the file number of the currently-playing file

AT+QUERY=5  //Query the file name of the currently-playing file
Return：test.mp3    //The currently-playing file is "test.mp3"


/**
 * @brief Play the file of the specified number
 * @param        n:File number(Play the first file if there is no such file)
 */
AT+PLAYNUM=5                       //Play file No. 5

/**
 * @brief Play the specific file
 * @param File path
 */
AT+PLAYFILE=/DF_REC/test.MP3        //Play the test.mp3 under DF_REC once

/**
 * @brief Amplifier On/OFF command
 * @param    ON, OFF
 */
AT+AMP=ON   //Turn on amplifier

/**
 * @brief Delete currently-playing file
 */
AT+DEL

/**
 * @brief Set baud rate (power-down save, valid after re-powering on)
 * @param    9600、19200、38400、57600、115200
 */
AT+BAUDRATE=115200  //Set baud rate to 115200

/**
 * @brief Prompt tone ON/OFF command (Power-down save)
 * @param    ON, OFF
 */
AT+PROMPT=ON   //Turn on prompt tone

//LED Prompt On/Off Command(Power-down save)
/**
 * @brief LED Prompt ON/OFF command (Power-down save)
 * @param    ON, OFF
 */
AT+LED=ON   //Turn on LED Prompt