HC-06 bluetooth module have interference

Question

my HC-06 have interference. I just have plugged it to my testing board and provided 5V. then paired it to my PC and used bluetooth serial terminal to communicate with it. everything is fine until I plug a wire to connect the TX/RX to my programming board. once TX is plugged in, the serial client on my PC start receiving random data. I have removed the wire from the board and it stopped. when I push the testing board with my finger near to the TX section, it start sending again. Do you have a suggestion ? it acts like I'm an antenna.

I discovered this after 2 hours of trying to communicate with it with raspberry pi pico to just make a LED ON/OFF. the program was simple, just send letter ( a ) to have led on and letter ( b ) to have led off, the thing is when I print what my UART is receiving, its a lot of random data instead of just ( a/b ). By the way, I have 2 bluetooth HC-06 modules and both are acting same

I want to know why I'm getting random data from my HC-06

Answer 1

• Make sure your grounds are tied together between your boards. This is the most likely problem if you're getting "antenna" effects. Something probably isn't grounded correctly.
• Make sure that you're driving your Tx/Rx lines at 3.3V, not 5V
  • I will assume that your board takes 5V for Vcc, since that is common, but remember that the HC-06 itself is 3.3V
  • If you have 5V logic, you can use a voltage divider resistors on the Rx line to get it to 3.3V.
• Probably not related, since the symptoms would be a bit different, but make sure your baud rate is set correctly on your other board (9600)