Output cut off

Projects Programming
1

Hello,

I do not understand how the output works. I modified a Bluetooth sample program to work with my HM-19 Bluetooth module:

#include <SoftwareSerial.h>
#define rxPin 10 // yellow
#define txPin 11 // green

SoftwareSerial BTSerial(rxPin, txPin); // RX, TX

void setup() {

  Serial.begin(9600);
  BTSerial.begin(9600);
  while(!Serial);

  BTSerial.println("AT+DISI?");

}

void loop() {

  // read from HM-19 and print in the Serial
  if(BTSerial.available())
  Serial.write(BTSerial.read());

  //read from the Serial and print to the HM-19
  if(Serial.available())
  BTSerial.write(Serial.read());
}

The output is:

OK+DISCS
OK+DIS1:00000000:00000000000000000000000000000000:0000000000:F33321aabbcc:-059
OK+DIS1:00000000:00000000000000000000000000000000:0000000000:F333B2aabbcc:-057
OK+DIS1:00000000:00000000000000000000000000000000:0000000000:6BA0C7aabbcc:-037
OK+DISCE

Now I replace BTSerial.println("AT+DISI?");

with

BTSerial.println("AT+DISI?");
delay(1000);
BTSerial.println("AT+DISI?");

and all I get is this:

OK+DISCS
OK+DIS1:00000000:00000000000000000000000000000000:000OK+DISCE

What did I do wrong that I got this cutoff output instead of getting the pre-modification output twice?

2

My first guess would be that you are running out of input buffer. Instead of starting to empty the buffer almost immediately you are waiting for a full second and then asking for more input before even starting to pull characters from the buffer.

3

johnwasser:
My first guess would be that you are running out of input buffer. Instead of starting to empty the buffer almost immediately you are waiting for a full second and then asking for more input before even starting to pull characters from the buffer.

Something like that was my first guess, too. But the other way round: It was the reason for me to add the delay, because

  Serial.begin(9600);
  BTSerial.begin(9600);
  while(!Serial);
  Serial.println("1");
  BTSerial.println("AT+DISI?");
  Serial.println("2");
  BTSerial.println("AT+DISI?");

only gives me

1
2

I added the 1, 2 to see if it's working at all.

4

My guess is that the module receiving the second command before the first command has completed was causing both to fail.
You should probably only send a command when you are immediately ready to receive the response and not send another command until the first response is complete.

5

Have a look at the examples in Serial Input Basics - simple reliable non-blocking ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

...R

6

johnwasser:
My guess is that the module receiving the second command before the first command has completed was causing both to fail.
You should probably only send a command when you are immediately ready to receive the response and not send another command until the first response is complete.

My guess exactly. That's why I put the delay in there.

Robin2:
Have a look at the examples in Serial Input Basics - simple reliable non-blocking ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

...R

I'll have look, thank you.