I can't connect to my HM-10 bluetooth module

Projects Programming
1

I tried the PIN codes 1234, 0000, 000000 to no luck, the phone tries to connect for some seconds and the red LED on the module stops blinking but afterwards it says "Unable to connect to HMSoft" and the LED starts blinking again.

I also can't send any commands through serial (I have it connected to my PC via Arduino Uno), both with the baud rate set at 9600 and 115200. I tried using both the Arduino IDE Serial Monitor and CoolTerm, but when I send a command I get no response back. I have it connected like this:

Arduino Uno ---> HM-10 Module
5V ---> VCC
GND ---> GND
TX ---> RXD
RX ---> TXD

Furthest I managed to go was connecting to it without a PIN with the app BLE Scanner, and then the LED stopped blinking, but I couldn't get it to bond with my mobile or send/receive any data at all.

2

there's only one serial interface (pins 0 & 1) on an Uno connected to the USB interface chip and used both to download code and access the processor via the Serial monitor.

did you connect the hm-10 to those same pins?

when i built a device using the serial interface and an UNO, i developed the code on a Mega which has 4 serial interfaces and only used the Uno when i put it to use.

i had a jumper to disconnect the RX pin from the rs-485 driver i used to reprogram the UNO

3

Hello, thanks for your response.
I did connect the RX and TX on the hm-10 to pins 1 and 0 on the arduino, but I tried again with unused pins (2 and 3) and still the same issue. This is my code:

#include <SoftwareSerial.h>
// RX=2, TX=3
SoftwareSerial HM10(2,3); 
void setup()
{
  HM10.begin(9600); 
  Serial.begin(9600);   
  delay(100);
}
void loop()
{
  if (Serial.available()>0)
    HM10.write(Serial.read());
  if (HM10.available()>0)
    Serial.write(HM10.read());
}

And my wiring connections look identical to this (Except my module doesn't have an EN pin, it has BRK and STATE pins)

image
image741×390 47.3 KB

4

again, the Uno only has one serial port

i forget how to establish a bluetooth connection. i don't believe you can see and serial monitor output with the hm-10 connected to pins 0&1. you'll have to disconnect it to program the Uno and then re-connect it to test.

perhaps you can write code that toggles the LED

  • if it successfully connects to bluetooth
  • receives a BT message
  • receives a particular BT message
5

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