How I can translate a struct as hex/base16

Projects Interfacing w/ Software on the Computer
1

I have the following sketch

typedef struct  {
  // Page that is transmitted
  unsigned int page;

  // Block that is transmitted
  unsigned int block;

  // A mumeric representation of the 32 byte segment that I send. 
  // I cannot send the page altogether, therefore a byte intexing is required
  uint8_t bytes_index;
  
  // Despite my buffer is 32 bytes the usable data may be less
  uint8_t length; 

  // Data buffer containing the data to be sent via serial
  byte data[BUFFER_LEN];
} usb_msg;

void setup() {
// SPI.begin();
 Serial.begin(9600);
 Serial.print(ACK);
}

void loop(){
  usb_msg msg;
  // Populate dummy data
  msg.page=1;
  msg.block=1;
  msg.bytes_index=2;
  msg.length = 10
  msg.data = [1,1,1,1,1,1,1,1,1,1];

  // Send it here
}

Is there a way to hex/base16 endode the msg before sending it through serial?

2

Serial.print(data_byte, HEX);

Leaves out leading zeros, and does not formatting symbols like "0x". Add those if you like.

3

Do you want the data sent as ASCII characters or as the raw binary data?

4

Do you want the data sent as ASCII characters or as the raw binary data?

As hex encoced ascii string.

5 
void loop() {
  usb_msg msg = {1, 1, 2, 10, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}};
  // Populate dummy data
  //msg.page=1;
  //msg.block=1;
  //msg.bytes_index=2;
  //msg.length = 10;
  //msg.data = [1,1,1,1,1,1,1,1,1,1]; //this will not work

  // Send it here
  byte* ptr = (byte*)&msg;
  for (size_t i = 0; i < sizeof(usb_msg); i++){
    Serial.print(*ptr >>4, HEX);
    Serial.print(*ptr & 0x0F, HEX);
    ptr++;
  }
  delay(60000);
}
6

It worked but I want to understant more the rationale behind your code.

So far I understand that via:

  byte* ptr = (byte*)&msg;

You actually convert the struct as a byre array. Also I understand that each byte must be encoded one-by-one as hex.

But I cannot understand why at line:

    Serial.print(*ptr >>4, HEX);

You actually divide the byte value with 2^4 = 16

Also, what is the reason that you actually do a binary and with 0x0F as well at line:

    Serial.print(*ptr & 0x0F, HEX);

Do you actually try to encode the first half (first 4 bits) and the latter half (other 2 bitsd) of the byte seperately, if yes why?
If yes why

7

Yes, The first line sends the upper 4 bits as a hex character, the 2nd line sends the lower 4 bits as a hex character. If you just print(*ptr, HEX) there will be no leading zero for numbers less than 0x10. As an example 0x01 0x01 would print as "11" instead of "0101".

8

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