Need to know how to send HEX values via SoftwareSerial on Arduino Uno

Question

I’m trying to write Android Uno code to send HEX values via SoftwareSerial but when watching the Serial Monitor the output isn’t what I expected or wanted, and I am not experienced enough yet to know what to do next.

I don’t know where the FFFFs come from to be able to eliminate them.

My desired output is:

<br>
AA130120<br>
AA0400AE

What I get is:

<br>
FFFFFFFFAA1311E<br>
FFFFFFAA20

My code:

#include <SoftwareSerial.h>
// Define the RX and TX pins to establish UART communication with the MP3 Player Module.
#define Pin_RX 0 // to RX
#define Pin_TX 1 // to TX
#define d_sleep 10000

// Define the required MP3 Player Commands:
static byte ccPlay[]   = {0xAA, 0x02, 0x00, 0xAC}; // Play:
static byte ccSetVol[] = {0xAA, 0x13, 0x01, 0x20}; // Set Volume (00-30):  

// Define the Serial MP3 Player Module.
SoftwareSerial MP3(Pin_RX, Pin_TX);

void setup() {
  // Initiate the serial monitor.
  Serial.begin(9600);
}

void loop() { // Play a song.
  ccSetVol[3] = {0x1E};
  send_command_to_MP3_player(ccSetVol, 4);
  delay(d_sleep);
  send_command_to_MP3_player(ccPlay, 4);
  delay(d_sleep);
}

void send_command_to_MP3_player(int8_t command[], int len){
  //Serial.print("\nMP3 Command => ");
  for (int i=0; i<len; i++) {
    MP3.write(command[i]);
    Serial.print(command[i], HEX); 
  }
  delay(100);
}

This doesn't compile for me; void send_command_to_MP3_player(int8_t command[], int len) should be void send_command_to_MP3_player(byte command[], int len) or void send_command_to_MP3_player(uint8_t command[], int len) — ocrdu, Dec 10 '20 at 17:19

ocrdu · Accepted Answer · 2020-12-11T00:40:41.930

0

Could you set the baud rate in the serial monitor to 9600Bd, run this code, and see if it spits out the bytes you expect in the serial monitor?

#define d_sleep 10000

static byte ccPlay[]   = {0xAA, 0x02, 0x00, 0xAC};
static byte ccSetVol[] = {0xAA, 0x13, 0x01, 0x20};

void send_command_to_MP3_player(byte command[], int len) {
  for (int i=0; i<len; i++) {
    //Serial.println(command[i], HEX);
    Serial.print(command[i], HEX);
  }
  //Serial.println();
  delay(100);
}

void setup() {
  Serial.begin(9600);
  delay(1500);
}

void loop() {
  ccSetVol[3] = 0x1E;
  send_command_to_MP3_player(ccSetVol, 4);
  delay(d_sleep);
  send_command_to_MP3_player(ccPlay, 4);
  delay(d_sleep);
}

edited Dec 11 '20 at 00:40

answered Dec 10 '20 at 17:27

ocrdu

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Looks to output the same thing. – bill z Dec 10 '20 at 23:56
AA 13 1 1E AA 2 0 AC – bill z Dec 10 '20 at 23:58
Allow me to explain please. These HEX values are displayed in Serial Monitor vertically but when I try to send you what I see, this utility arranges them horizontally with a space. – bill z Dec 11 '20 at 00:00
I don't want the CR/LF but I do want the leading zeros please. – bill z Dec 11 '20 at 00:12
I'll edit the code. I can't give you leading zeroes though, but that doesn't matter for sending to the MP3 player; the right bytes will be sent if you add the MP3 player code back in, they will just display without the leading zeroes in the serial monitor. – ocrdu Dec 11 '20 at 00:15
Is there an advantage to using Softwareserial lib and send TX/RX on different pins or not and use the recognized pins 0 & 1 on the UNIO? – bill z Dec 11 '20 at 00:52
I don't know, I never use SoftwareSerial. You could ask on Arduino. – ocrdu Dec 11 '20 at 00:55
You're welcome. Don't forget to put the SoftwareSerial stuff back in, and the MP3.write(command[i]);, and so on; I removed some things to isolate the problem. – ocrdu Dec 11 '20 at 01:08
It was suggested to add a line to my code so when the Hex character is less than 16, to serial.print("0");. That makes Serial Monitor look good, but it doesn't do positive things communicating with the MP3 Player. – bill z Dec 11 '20 at 17:29
No, it just looks better. The MP3 player just gets a byte, and doesn't care if that byte looks like 0 or 00 to you; the byte sent is simply 0. – ocrdu Dec 11 '20 at 17:33

Need to know how to send HEX values via SoftwareSerial on Arduino Uno

1 Answers1