Chrg led on arduino mrk gsm 1400 blinks


My charge Led on the mrk gsm 1400 blinks. Also, I can't connect the arduino to the pc. Before this problem accured, the built in Led blinked also. but now only the charge led blinks. I connected the tf mini plus lidar sensor to the arduino. on the 5v output, the ground, pin14(tx) and pin 13(rx). Is my arduino damaged? If yes, why? If no, wats going on? How can I fix this problem?

I would be thankfull for an answer.

Try this:

  1. Press and release the reset button on your board quickly twice. If the microcontroller is still working correctly, you should now see the LED on the board pulsing, which means the bootloader is running.
  2. Select the port of your board from the Tools > Port menu. The port number may be different when the bootloader is running so don't assume you already have the correct port selected.
  3. Attempt an upload in the Arduino IDE.

I tried this, but it didn't work. The chrg Led still blinked as if nothing happend.

So did you actually see the USB port in step 2?

no. normaly my pc makes a sound when i plug in a device. The pc didn't even noticed that i pluged something in.

My previous instructions were not as specific as they might have been. By "the LED", I meant the LED on the board that is labeled on the silkscreen as "L". It is next to the 5V pin header. Do you see that LED pulsing after you do the double reset described in my previous reply?

No, this Led didn't light up.

Have you got a link to that?

If it did work and now doesn’t and you have double clicked the reset, then it looks like it might be damaged.

What did you do differently between it working and not working?


The first Tf mini plus that I had, was damaged because I forgot to remove the plastic on the glas. The Lidar always messured a distance of 0. Then, I got a new one. And since then I have this problem with the arduino. I am not sure, but I think I made everything the same like on the first Lidar. Of course this time I removed the plastic from the glas befor I ran current threw it.

Yes link, that is the name for a URL that points to the address of the web page where you ordered it from.

All Arduinos have a very limit current capability for driving things from the 5V pin. Also your Arduino is a 3V3 system and if your device is powered by 5V it is likely that it will send a 5V signal into your Arduino, which will be enough to kill it.

This is the data sheet for the lidar.

SJ-GU-TFmini-S-01 A00 Datasheet.pdf (201,0 KB)

When the "L" LED doesn't pulse after a double reset, it means one of two things:

  • The bootloader on the MKR GSM 1400 is missing or corrupted
  • The board is physically damaged

In the case of physical damage, it's likely the board is beyond economical repair.

In the case of a bootloader problem, the board can be recovered by doing a "Burn Bootloader" operation. I'll provide you with instructions for doing that. However, you should be warned that bootloader problems are relatively rare compared to people burning up their Arduino boards and the process of burning the bootloader is quite complex and requires additional hardware. So don't get your hopes up too much for this to save your board. Probably you would be best to expect only an entertaining and interesting experiment as return for your efforts.

Note: alternative methods are described at the end of the post.

Using an Arduino board as the programmer

You'll need

  • An extra Arduino board that runs at 3.3 V to use as the programmer.
    • Any of the SAMD architecture boards (e.g., MKR boards, Nano 33 IoT, Zero) will work fine.
    • The sketch is too large for the AVR architecture boards (e.g., Mega), so they can't be used.
    • The sketch doesn't compile for the Nano 33 BLE, so it can't be used.
  • A way to make the connections to the SWD pins on your target Arduino board. For the Nano 33 IoT and the MKR Boards other than MKR1000, I like to use a 0.1" pitch 2x3 POGO adapter. You could also solder wires to the test points if you prefer. On the MKR boards other than the MKR1000, the SWD header is on the bottom of the board and is the footprint for a 0.1" pitch 2x3 SMD header (e.g., On the MKR1000, it is a 0.05" pitch 2x5 male header on the top of the board, which you will need an adapter and cable for.


  1. Select Sketch > Include Library > Manage Libraries... from the Arduino IDE's menus.

  2. Wait for the download to finish.

  3. In the "Filter your search..." field, type "Adafruit DAP library".

  4. Press Enter.

  5. Click on "Adafruit DAP library by Adafruit".

  6. Click the Install button.

  7. Wait for the installation to finish.

  8. Click the Close button.

  9. Select File > Examples > Adafruit DAP library > samd21 > flash_MKR_bootloaders from the Arduino IDE's menus.
    (despite the "MKR" in the sketch name, this also supports the Nano 33 IoT)

  10. Select your programmer Arduino board from the Tools > Board from the Arduino IDE's menus.

  11. Select the port of the programmer Arduino board from the Tools > Port from the Arduino IDE's menus.

  12. Select Sketch > Upload from the Arduino IDE's menus.

  13. Wait for the upload to finish successfully.

  14. Unplug the programmer Arduino board from your computer.

  15. Connect the programmer Arduino board to the target Arduino board as follows:

    Programmer Target
    VCC +3V3
    1 SWDIO
    2 SWCLK
    0 RESETN

    SWD pads on MKR boards other than MKR 1000:
    MKR1000 SWD header pinout:
    MKR1000 SWD
    Nano 33 IoT SWD pads:
    Nano 33 IoT SWD

  16. Plug the USB cable of the programmer Arduino board into your computer.

  17. Select Tools > Serial Monitor from the Arduino IDE's menus.

  18. Select "No line ending" from the dropdown menu near the bottom right corner of the Serial Monitor window.

  19. You should see some instructions for using the sketch in the Serial Monitor output field. This includes a menu of the boards supported by the sketch:

    Select Arduino MKR board to erase and flash with bootloader:
    Z     -> Arduino Zero (6504 bytes)
    MZ    -> Arduino MKR Zero (6408 bytes)
    1000  -> Arduino MKR 1000 WIFI (6408 bytes)
    1010  -> Arduino MKR WIFI 1010 (7984 bytes)

    Find your target Arduino board on the list and note the code written to the left of it on the list.

  20. Type the code for the target Arduino board in the Serial Monitor's input field.

  21. Click the Send button to the right of the Serial Monitor input field.

  22. The Serial Monitor output field should now show the board you selected and the progress of flashing the bootloader to the target Arduino board. Wait for it to show "Done!"

  23. Unplug the programmer Arduino board from your computer.

  24. Disconnect the programmer Arduino board from the target Arduino board.


These are some alternatives to the "Adafruit DAP" method I described above. I'll share one here:

Using a CMSIS-DAP debug probe as the programmer

If you have a CMSIS-DAP compliant debug probe, you can just do this instead:

  1. Connect the debug probe to your Arduino board.
  2. Select Tools > Programmer > Atmel EDBG from the Arduino IDE's menus.
  3. Select Tools > Burn Bootloader from the Arduino IDE's menus. - The "Burn Bootloader" process should now finish successfully.

I use this little open source debugger.

It seems to me that the board is damaged. How can I connect the lidar without damaging the board?
And even if the bootloader is the problem, I wount invest that much time to fix that.

While you did post a link to a data sheet it was not a very good link. It did show that the data back would be at 3V3 so that is fine. However it didn’t say anything about he pins and what they are. So as a data sheet it is quite a poor o e. Is there something better?

TFmini-Plus-T-01 A04_Product Manual.pdf (1,0 MB)

Thanks, now all we need to see is the schematic of how you have connected it up to your Arduino.

Thanks for the picture but I did ask for a schematic. The problem with the picture is that it is not at all well lit so I am having great difficulty identifying if it is the green or black wire that comes from the Molex connector. It also doesn't help that the wires fly off the top of the picture and back into shot again. Also pin 3 from the left should be blue/green but it looks like white on pin 2.

However I think I can check what I wanted to. I was after seeing how you have connected up the TX and RX connections and it looks like you are getting that right.

So have you tried removing all connections to the LiDAR and just try and program your Arduino. If that fails then I suspect that is damaged as well.

Do you have access to any test equipment? An Oscilloscope would be good to see if you are getting anything out of the LiDAR when only the power supply is connected. Then you could also check the claim that it is only a 3V3 signal.

I notice that the MKR GSM 1400 board takes a current of min 100 mA / max 190 mA and on top of that you are driving the LiDAR directly from the USB 5V and that board takes a peak current of 140mA. So the total peak current is 330mA. While that is within what the USB should be able to deliver I would think it is pushing it. We often say here that the Arduino is not a power supply. Maybe try an external 5V supply to power things?

No I can't programm the arduino. I can't even connnect it to the pc.
No I don't have a Oscilloscope. I only have a voltmeter.