Hi, I have been recently working on a project including the DFPlayer Mini, and I am running into some trouble with the following error: Serial receiving error(a frame has not been received completely yet)

This is coming from the printError() function in the DFPlayerMini_Fast library.

I get a similar error if I use the DFRobotDFPlayerMini library: SerialWrongStack Error

Not sure what is wrong, I have it wired the same as the diagram on the wiki: https://wiki.dfrobot.com/DFPlayer_Mini_SKU_DFR0299

Both of these errors occur when I try to start playing music by pressing the play/pause button

Thanks for any help/suggestions.

Here is the entirety of my code, it adds code for rotary encoder and LCD:

#include <FireTimer.h>

#include <DFPlayerMini_Fast.h>

// include the library code:
#include <LiquidCrystal.h>

// Rotary Encoder Inputs
#define CLK 2
#define DT 3
#define SW 12

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 11, en = 10, d4 = 7, d5 = 6, d6 = 5, d7 = 4;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

// Create the Player object
DFPlayerMini_Fast player;

//this is so that we can declare the LCD_Update method properly
void LCD_Update(String lineone, String linetwo="");

String currentLCDline1 = "Loading.........";
String currentLCDline2 = "#-#-#-#-#-#-#-#";

//Stores current play/pause state (starts paused)
int playpause = 0;
//number of files in sd card
int FILENUM = 0;
//starts instead of resumes if its our first time
bool firstStart = true;
//stores last button press type
int lastSwitchState =0;
//for long press/short press code
long buttonStartTime = 0;
long longPressTime = 250;

bool wasJustPressed = false;

//rotary encoder
int clkPinLast = LOW;
int clkPinCurrent = LOW;

///methods needed to be used in start=====================================================================

//updates LCD to lineone, with the ability to change line two as well
void LCD_UpDate(String lineone,String linetwo="")
{
lcd.clear();

lcd.print(lineone);
currentLCDline1 = lineone;
if(linetwo != "")
{
lcd.setCursor(0,1);
lcd.print(linetwo);
lcd.setCursor(0,0);
currentLCDline2 = linetwo;
}
else
{
currentLCDline2 = linetwo;
}
}

//=====================================================================================================

void setup() {
// Init USB serial port for debugging
Serial.begin(115200);

Serial.println("Setting up");
// Set encoder pins as inputs
pinMode(CLK, INPUT);
pinMode(DT, INPUT);
pinMode(SW, INPUT);
// Init serial port for DFPlayer Mini
Serial1.begin(9600);
Innit_LCD();
//initialize the music player
Innit_SDPlayer();
}

//main loop===========================================================================================
void loop()
{
//check rotary encoder (button and all)
updateEncoder();

// //Serial.println("Playing");
// //check dfrobot
// if (player.available()) {
// //update SD player
// printDetailAndUpdateSong(player.readType(), player.read());
// }

player.printError();
delay(50);
//update lcd with our strings
LCD_UpDate(currentLCDline1,currentLCDline2);

}

//lcdplay innitilization
void Innit_LCD()
{
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
LCD_UpDate(currentLCDline1,currentLCDline2);
delay(1000);
}

//sd card player functions
//==================================================================================================
void Innit_SDPlayer()
{
// Start communication with DFPlayer Mini
if (player.begin(Serial1, true))
{
Serial.println("OK");
//set timeout for communication
player.setTimeout(2000);

LCD_UpDate("SD Innitalized");
FILENUM = player.numSdTracks();
// Set volume range (0 to 30). some day maybe have a long press for the SW allow this volume to be changed...
player.volume(20);

} else {
Serial.println("Connecting to DFPlayer Mini failed!");
//display on LCD
LCD_UpDate("SD Player Failed");
}
}

//play or pause player
void playPauseSD()
{
if(playpause == 0)
{
if(firstStart){
player.startRepeatPlay();
firstStart = false;
}
playpause = 1;
player.resume();
}
else
{
playpause = 0;
player.pause();
}
}

//=================================Rotary Encoder methods========================================================
void updateEncoder(){
int switchState = digitalRead(SW);

//button code
if (switchState == HIGH&& switchState != lastSwitchState) {
wasJustPressed = true;
//was pressed, lets start counting how long it is held down.
buttonStartTime = millis(); //this is okay because this wont run unti, there is a low and then high again (another button press)
}
else if(switchState == LOW)
{
long endtime = millis();
//button was either just released or never pressed, so lets check to see which it is
if(wasJustPressed)
{
//look at how long it was held down, if its a short press play/pause the music (stop - start = time elapsed0
if((endtime-buttonStartTime) < longPressTime)
{
//short press code
//play or pause
playPauseSD();
delay(30);
if(playpause == 0){
Serial.println("Paused");
currentLCDline1 = ".....Paused.....";
currentLCDline2 = "";
}else if(playpause == 1){
Serial.println("Playing");
currentLCDline1 = "Playing from SD";
currentLCDline2 = ("Num: "+String(player.currentSdTrack())+"/"+FILENUM);
}

}
else
{
//long press code
Serial.println("Pressed for over longPressTime milliseconds");
}
wasJustPressed=false;
}
}
lastSwitchState = switchState;

//make sure that we are not paused
if(playpause == 1){
clkPinCurrent = digitalRead(CLK);

if ((clkPinLast == LOW) && (clkPinCurrent == HIGH)) {
if (digitalRead(DT) == HIGH) {
//change song forward
Serial.println("Next...");
player.playNext();
delay(30);
//display on lCD
currentLCDline1 = "Playing from SD";
currentLCDline2 = ("Num: "+String(player.currentSdTrack())+"/"+FILENUM);
}
else {
//change song backward
Serial.println("Previous..");
player.playPrevious();
delay(30);
//display on lCD
currentLCDline1 = "Playing from SD";
currentLCDline2 = ("Num: "+String(player.currentSdTrack())+"/"+FILENUM);
}
}

clkPinLast = clkPinCurrent;
}
}