HC-08 bluetooth module not responding to AT commands

Hello everyone :slightly_smiling_face: ,
I have a Keystudio HC-08 bluetooth module and its wiki at:
It doesn’t respond to AT commands.

This is the circuit:
(arduino) pin 8 [Software TX] > (hc08) RX [with voltage divider (1 KOhm – 2 KOhm)]
(arduino) pin 4 [Software RX] > (hc08) TX
(arduino) 5 V > (hc08) VCC
(arduino) GND > (hc08) GND

I’ve tried with and without voltage divider.
I’ve tried different bauds including 9600, 57600 and 115200.

This is the code:

#include <SoftwareSerial.h>

SoftwareSerial sS(4, 8); // RX, TX

void setup() {
  Serial.println("Ready for AT commands");

void loop() {
  if (sS.available()) {
  if (Serial.available()) {

Anyway, IT DOES CONNECT to android (using the Serial Bluetooth Terminal application) but even then, if I type something, it does not appear on Arduino IDE’s Serial monitor.
I didn’t find anything useful in the forum or in the web… Any ideas?
Thankyou very much :smiley:

You seem to be doing everything right so maybe your RxTx connections are mechanically faulty. Having the phone connect only proves that power to Bluetooth is kosher. It tells you nothing about the connection Arduino<>Bluetooth, i.e. the RxTx cables.

I hooked up an original Arduino Uno board, brand new male female jumpers directly to the hc08 without breadboard and nothing :muscle:

Well, I surrender to the fact that my module is broken.

As a last resort, try reversing the Rx-Tx wires. I only say this because you are using software serial.

Did that, doesn’t work.
I’ve tried every possible combination, even using directly pins 0, 1 without software serial.

OK. I’m not familiar with this module but I assume it is on a breakout board like other HC-0x. These devices are not usually known to be badly made but I have heard of a couple with solder bridges across connections. , probably the pins. A close inspect there might be the last card in the pack…

Playing with the Serial Bluetooth Terminal app, I found out that there is exchange of information, ie if i write something on the app, it appears on the monitor and if I write something on the monitor it appears on the app. Therefore the software uart is working, right?
So I was wondering: is the module in AT mode when it turns on? As far as i know it should be because it doesn’t have a button (like the hc-05) and it is not mentioned in the wiki.

Ok, for whatever reason, it worked for like 3 times (answered to AT with OK) and now stopped again.
How could be the connection be faulty if everything i’m using is brand new? :sweat_smile:
Btw i checked under a magnifying glass the soldering and it seemed genuine to me. No bridges or bad junctions.

It should be in AT mode at power on, not because it doesn’t have a button but because it is a BLE device.
And while we are on this tack, you may already know that Morich’s terminal app must be in BLE mode in order to connect with BLE devices. I guess they are all like that, but this is the only one I have actually used.

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