[SOLVED] HC-05 length of message problem

I bought two HC-05 modules on eBay.

They seem to work. I have the voltage divider for the RX. The HC-05 baud rate has been changed to 115200.

I am using a Bluetooth Terminal on my Android smartphone to send the HC-05 text.

If I send a relatively short message of 4 or 5 characters, the HC-05 receives it okay. But if I send a message of 10 characters, some of the letters are wrong.

I am using the following sketch to see what the HC-05 is receiving.

What else should I be doing to make the communication more robust?

#include <SoftwareSerial.h>

SoftwareSerial BTserial(13, 12);
// Connect the HC-05 TX to Arduino pin D13. 
// Connect the HC-05 RX to Arduino pin D12 through a voltage divider.
void setup() 
    Serial.println("Arduino is ready");
    // HC-05 has been set to 115200 by another sketch
    Serial.println("BTserial started at 115200");
void loop()
    char aByte;

    if (BTserial.available() > 0)
        // text arrived in from BT serial

        aByte = BTserial.read();



Software serial does not work properly at 115200 Baud.

jremington: Software serial does not work properly at 115200 Baud.


Is this listed somewhere? If not, it should be. https://www.arduino.cc/en/Reference/SoftwareSerialBegin

Would 57600 be reliable?

Try it and see. The problem has been mentioned many times in this forum.

I've switched back to 9600.

The 9600 seems fast enough for a human typing on the Bluetooth Terminal so I will stick with that for now.

Thank you.