Serial hex output?

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello,

I'm trying to output hex commands via serial, but I'm having a little trouble.

long int header = 709248400;

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

void loop()
{
  int input;
  int output;
  
  input = 1;
  output = 1;
  
  take(input, output);
  
}

void take(int input, int output)
{
  Serial.println(header, HEX);
  
  int out1;
  int out2;
  
out1 = 0x10 + (input - 1);
out2 = 0xA0 + (input - 1);
data[0] = out1;
data[1] = 0x00;
data[2] = 0x00;
data[3] = out2;
    
    for(int i = 0; i < 4; i++)
    {
      Serial.print(data[i], HEX);
  }
  
  
}

The code I am trying to get it to output is this:

2A 46 45 90
10 00 00 A0

This is what I'm getting:

2A 46 45 90
10 00 A0

Even if I manually serial.print the two 0x00, I only get one 0x00.

I'm trying to control a video router with an RS232 interface. I was able to dump the serial output of the program that controls it into a text file, where I got the hex data above for one of the commands. Am I on the right track? Any ideas? Thanks.

2

My guess based upon nothing more than your code and the behavior you are describing: Serial.print() does not print the leading zero of a hex number, so when you print 0x00 you get 0, and when you print two 0x00 in a row, you get 00.

Try printing 0x00 four times in a row and see if you get 00 00.

  • Ben
3

Thanks - I believe I tried printing just one 0x00 and I think it gave me the same result, but I'll try printing four of them.

4

I wonder if you solved the problem, I try to send hex code: 1B 46,
The output I read on TX is 67 2F from the code Serial.print(0x1B,HEX);

Someone an idea to define serial.print to get 1B 46?

5

From the OrangutanLCD library:

// display a hex nibble (a single hex digit) at your current cursor location
void OrangutanLCD::printHexNibble(unsigned char nibble)
{
      if (nibble < 10)
            send_data('0' + nibble);
      else
            send_data('A' + (nibble - 10));
}

// display a two-byte value in hex (0000 - FFFF) at the current cursor location
void OrangutanLCD::printHex(unsigned int word)
{
      printHex((unsigned char)(word >> 8));
      printHex((unsigned char)word);
}

// display a single-byte value in hex (00 - FF) at the current cursor location
void OrangutanLCD::printHex(unsigned char byte)
{
      unsigned char val = byte >> 4;
      printHexNibble(val);            // display high byte high nibble
      val = byte & 0x0F;
      printHexNibble(val);            // display high byte low nibble
}

You could pretty easily modify this to transmit hex over the UART. Just change send_data() in printHexNibble() to whatever serial function transmits a single character and change the functions to be straight C (i.e. remove the "OrangutanLCD::" part)

  • Ben