Help on read hex from serial

Projects Programming
1

I have spend more than 8 hours on this. Please help.

I'm using MCU ESP8266 and it connect rx and tx to another voice recognition module.

The module send hex when get specific command.

So I want to read the hex I get then perform other tasks.

The hex is fixed.

So my goal is when I received F4 06 03 FF print Yes.
when I received F4 06 05 FF print no.

I only successful work on reading serial using string. But hex those thing too difficult for me.

Anyone can give me an example code?
Apperaciate that. Thanks

2

Below is the example code for handle with serial for the voice module from seller.
But I'm not able to convert it to arduino.

static void _hb_uart_recv(char *buf, int len) 
{
  int i;
  static uint8_t i_c;
  static bool start_rec_flag = 0;

  for (i = 0; i < len; i++) 
  {
    LOGR(TAG, "%02x ", (uint8_t)buf[i]);

    if ((uint8_t)buf[i] == 0xF4)            //Head Ok, starting to receive
    {
      i_c = 0;
      start_rec_flag = 1;
    }

    if (start_rec_flag == 1) 
    {
      rec_buf[i_c] = (uint8_t)buf[i];
      i_c++;

      if (i_c > 3)                         //6 byte received 
      {
        i_c = 0;
        start_rec_flag = 0;

        if(rec_buf[0] == 0xF4 && rec_buf[1] == 0x06 && rec_buf[2] > 0x00)
        {
            switch (rec_buf[2])
            {
            case 1: user_player_play(AUDIO_PLAY_REPLY, "101"); break;

            default:
              break;
            }
            memset(rec_buf,0,sizeof(rec_buf));
        }
          memset(rec_buf,0,sizeof(rec_buf));
        }
          memset(rec_buf,0,sizeof(rec_buf));
        }
      }
    }
  } 
}
3

could you provide a link to the module or even better the UART protocol documentation that is being used?

4

There is no UART protocol documentation.

The only documentation I got was When I say:
Hi xxx. I get F4 06 01 FF
Turn onf the light. I get F4 06 02 FF
same as other commands.

I can use serial monitor to get those hex when I connect directly to the module.
The problem now is just using ESP8266 to read those hex under Arduino.

5

I would suggest to study Serial Input Basics to handle this, the last part is about Binary data which is your case

(what's the module's name / reference?)

6

[quote="sasukebinbin, post:4, topic:849987"]
F4 06 01 FF[/quote]

in general, information is serially transmitted in either ASCII or binary (e.g. ethernet). i think what you asking is how to translate an ASCII string formatted as hex data into non-ascii values

sscanf () is one approach

7

I don't think so. clearly the module is using a binary protocol if ((uint8_t)buf[i] == 0xF4)

it would be interesting to have more than snippets (Snippets R Us!) and see how _hb_uart_recv() is being called, likely by another function listening to the Serial input and building a buffer (buf) which will then be parsed to extract a command into the rec_buf buffer. it seems 0xF4 is the start marker

8

so a Serial.read() might return 0xF4 and the terminator byte is 0xFF

9

may be...
not knowing what the device is nor the protocol does not help.

the head marker might actually be 0xF4 0x06

looking at the snippet it seems that a command can be either 4 bytes or 6 bytes long (may be, if we trust the comment) but it seems they trigger a command without looking at the other bytes but you need to have received more than 4 bytes. so the FF might not be the end...

@sasukebinbin - I'd say assume that the start marker is 0xF4 and collect bytes until a timeout or 0xFF and then just compare with your values

the tutorial would get you going. try that and post your progress

10

Thanks everyone for the reply.
I have figure out how to achieve this.
And it's really simple.

Just use the example code for readBytes

const int BUFFER_SIZE = 50;
char buf[BUFFER_SIZE];

void setup() {
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}

void loop() {
  // check if data is available
  if (Serial.available() > 0) {
    // read the incoming bytes:
    int rlen = Serial.readBytes(buf, BUFFER_SIZE);

    // prints the received data
    Serial.print("I received: ");
    for(int i = 0; i < rlen; i++)
      Serial.print(buf[i]);
  }
}
11

That should work most of the time, it will be a bit slow because there is a 1s timeout (by default) for readBytes() to return if no new byte is coming through (and seems you get only 4 or 6 bytes and your buffer is 50) . That will add visible latency to your handling of the recognised sentence.

12

Thanks man.
I can not feel the delay.
But I actually get 4 bytes. So what's the buffer size I should set here?

13

But I actually get 4 bytes. So what’s the buffer size I should set here?

then make it 4 would be a minimum. 6 would get a bit safer, there would be a delay but if it doesn't bother you that might actually help with synchronising

14

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