Bluetooth module based on HC-05 does not offer reset pin to enter AT mode

Projects Networking, Protocols, and Devices
1

Hi guys,

some days ago my new bluetooth module from ebay arrived. Now I would like to enter AT mode in order to change the device name, change passkey, connect to other devices etc. (The normal serial transfer mode works fine.)
On the internet it says I need to pull the key pin high while using the reset pin in order to enter AT mode. Unfortunately, my module does not provide a reset pin, it has only a key, an RXD, a TXD, a 0.5 VCC, a 3.3 VCC and a GND pin. But there are other modules based on the HC-05 which do not seem to have a reset pin either.
So does anybody know, how I can simply get into AT mode? I have already found a good document on AT mode here but nothing concrete dealing with my problem.

Thank you in advance.

Best regards from Germany
Birk

2

I have found the solution now:

void setup() {
  Serial1.begin(38400);
  Serial.begin(9600);
  pinMode(17, OUTPUT);
  digitalWrite(17, HIGH);
  delay(20);
  Serial1.println("AT+VERSION?");
  delay(300);
  while(Serial1.available())
    Serial.write(Serial1.read());
}

void loop() {
  // put your main code here, to run repeatedly: 
  
}

This code works, while my pin 17 is connected to the key pin of the module. I just had forgotten to set the pin mode to OUTPUT, therefore it did not work :blush: