Laser range finder hack

Today I found  a PLR 15 laser range finder from Bosch for 45 Euro in a German DIY store. I bought and disassembled it to see if it could be used as a laser ranger finder in robotics. The main issue will be to debug the communication protocol. I hope it outputs distance measurements over serial

This is a companion discussion topic for the original entry at

Sniff lcd output

Sure the range finder will output on the lcd, and you can listen here to get well formed data. Maybe it’s a proprietary protocol but it would be worth to try!


I have Purchased a PLR15 and I am trying to decipher the Debug port. I am not sure how I did it, but I managed to make the screen display RS232. So I will try to get there again and post instructions on how I did it. I hope this helps someone to get there faster with the hack. 

If you start with the left side of the seven Debug Pads on Marcus B’s pictures above [and call the leftmost pin, 1] . I think I got it to to show rs232 by bridging pins 1&2 I also found that bridging pins 6&7 seems to wake the unit. BUT PLEASE BE CAREFUL I have not done any real testing to confirm If I am doing something that won’t kill the unit. I have already killed one while playing around with the circuit board power regulator.

Magnetic Sensor

There is a small surface mount component on the front of the circuit board on the right hand side above the last unused button pad. (See Marcus B’s Pictures above).

This component is a magnetic switch. I just wraped a small magnet in a piece of paper and used some electrical tape to hold it above the unit. 

Note the unit will shut down after about 5 minutes of inactivity, so just press the measure button to wake it or remove and replace the magnet.

Plr 15 range finder
How did you open the case? I’removed the 4 screws in the battery compartment but cant get further. Thanks.

How to read data


Did anyone find out how to read data from this rangefinder?

I have found communication pins on vertical circuit, but I can’t read the data properly. I  tried almost every possible combination of UART parameters(baudrate, parity check, bit count), but still no luck. I am starting to think that is SPI. 

There is connection between vertical and horizontal board. There are 9 pins connectiing both boards. Pins on the left side seems to be communications pins. (1 and 3 ). When You hold the measurment data stops flowing on these pins.



Debug port - pin description


I have found the function of the pins of the debug port. I have remove the optics unit, and then with ohmic measure the PCB-tracks from debug-port to the processor. The Processor is a STM32F051R6 from ST.

  1. NRST to STM32F051R6  Pin 7
  2. Debug-pin SWDIO from STM32F051R6  PA13 Pin 46
  3. Debug-pin SWCLK from STM32F051R6  PA14 Pin 49
  4. 0V GND
  5. 0V GND
  6. +3V
  7. RX/TX (RS232/TTL) with first resistor 5k to STM32F051R6  (USART1-TX) PB6 Pin 58 and with second resistor 5k to STM32F051R6  (USART1-RX) PB7 Pin 59


I think, it is a command to pin 7 needed, to start the communication. Caution RX and TX are working together on the same debug pin no. 7.


please tell me the number of the display model - thank you

**First communication **

Send to debug pin 7 with 9600 baud, 8 data, 1 stop, no parity a command higher or equal than C0h. The response is always the same after 60ms with 3 bytes: 01h 00h FAh. And the laser go never in the power on state. Only the LCD backlight is on. Anyone have a good idea for the communication?

Hello,I’m going to buy BOSH


I’m going to buy BOSH PLR 15 for using it with Arduino in my project.

Is there a way to connect it to Arduino and measure distance via program code and get result into program?

Please advice.

using with Adruino

Hello, I’m going to buy BOSH PLR 15 for using it with Arduino in my project. Is there a way to connect it to Arduino and measure distance via program code and get result into program? Please advice.


Hello sidaba,

Would you please share info about how did you connect your PLR15 to COM port?

Or how did you manage to send command and get responce from it?

I want  to connect it also and check some commands.

Thank you.


Hi d00m178

Below is my circuit and the schematic. 




After power up 0V to 3,2V, yo can measure 0V at debug pin 7 from bosch laser. Now you must push the push button for 1s, then do you measure >3V at debug pin 7. Now you can start the communication.

Send commands higher or equal C0h with 9600/8/1/N  then you can receive after 60ms:  01h 00h FAh

Good luck! I hope you can read the distance over the RS232.

1 Like

Sniff lcd display
Good idea! Does the lcd is an I2c bus driver .?

Can anyone please help me to recognize parts, marked on the picture?
Thank you1547235640388e9815278862008e9aae6ef25ecb

Hi @A32
if I had to guess, I’d say the big part is an optocoupler and the 3-leg is a Mosfet.

Thank you. I need to replace both and require their exact parameters/title