I am having problems getting the Bluesmirf Mate Silver (RN-42) into command mode once I have switched to HID mode. I have bought a second new Bluesmirf Mate Silver to confirm my issue.

I soldered the Bluesmirf and connecting to Arduino Uno. I used the ‘Example code: Using Command Mode’ from https://learn.sparkfun.com/tutorials/using-the-bluesmirf to successfully enter command mode.

I then entered the following commands in command mode (leaving out the comments):

SM,5   // Mode = 5, (any) Auto reconnect
SA,2   // Authentication Mode 2 (SSP, "just works" mode)
S-,myName  // // Set BT Name, This short name with no spaces is Picked up ok on windows
S~,6   // Enable HID on reboot
R,1    // Reboot to lock in perameters

Next I use a PC and pair with the bluetooth ‘keyboard’ I have created above. I am able to use the Bluetooth and Arduino sketches to write into notepad on the bluetooth connected PC.

However now I cannot get back into command mode to make changes to the Bluesmirf config. Trying to use the example code above I can see ‘$$$U,9600,N’ typed into notepad on the connected PC each time I load the sketch, rather than being used to enter command mode.

How do I get back into command mode after HID mode has been triggered.

1 Answer 1


I believe that the problem is caused by the mode I entered. According to the datasheet on pg 10 Auto-Connect Master Mode (SM,3) enters high speed mode and this connection cannot be broken via commands or software break characters. It goes on to explain that both Auto-Connect DTR Mode (SM,4) and Auto-Connect ANY Mode (SM,5) (which I used) function like Auto-Connect Master Mode (SM,3), so I guess that in these modes the $$$ escape characters cannot be used to enter command mode either.

I was able to resolve this by performing a hard factory reset on the Bluesmirf Mate Silver (RN-42). I previously tried following a couple of you-tube tutorials that weren't very clear and didn't have any success. I looked at the instructions in this thread titled 'Factory Reset the RN-41 or RN-42' to get me on the right lines.

This worked for me:

  1. Connect the Bluesmirf Mate Silver GND pin to GND and disconnected all other pins
  2. Connect a wire to 3.3v on Ardunio
  3. Load the Ardunio with an empty sketch, and keep it powered on
  4. Touch the 3.3v wire repeatedly (3+ times) to the GPIO4/PIO4 connection hole on the Bluesmirf. This is a third of the way down one edge of the board.
  5. Factory reset should now be complete - note I didn't see any indication lights during this process.

Then I could wire up the Bluesmirf as normal and use ‘Example code: Using Command Mode’ from https://learn.sparkfun.com/tutorials/using-the-bluesmirf to successfully enter command mode.

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