Discussion Forums

Duo stuck on green led flashing



My RB Duo seems to be stuck on green LED flashing (like it was searching of a Wi-Fi access point). Can’t get it to setup mode, can’t initiate dfu, doesn’t respond to TTY via PuTTY.

Any ideas on how to do a factory reset maybe?


Generate wifi network

Got it to “unstuck” for a moment via Link and been able to re-config Wi-Fi credentials, but it doesn’t connect to the network.
I’m unable to put it in DFU mode (not via Link, nor when connected directly to the Duo).


Hi @norbert,

When your Duo was flashing green LED, it means that it is trying connecting to the access point you just config before. It will keep trying if the password is incorrect or the router is out of range. Anytime as long as the Duo do not crash, you can keep holding the SETUP button for 3 seconds to enter the setup mode (aka listening mode) to config the WiFi profile again.

KEEP HOLDING the SETUP button and have a shot on the RESET button:

  1. If you release the SETUP button during the following 0~3 seconds(flashing magenta), Duo will enter the Safe Mode.

  2. If you release the SETUP button during the following 3~6 seconds(flashing yellow), Duo will enter DFU Mode.

  3. If you release the SETUP button during the following 6~9 seconds(flashing green), Duo will enter Factory Reset Mode, without clearing the stored WiFi profiles

  4. If you release the SETUP button during the following 9~12 seconds(flashing white), Duo will enter Factory Reset Mode, with clearing the stored WiFi profiles.

  5. If you keep holding the SETUP button more than 12 seconds, Duo will perform the factory reset and then repeat from case 1, unless you release the SETUP button before factory reset completed.

Regarding to these different mode, please refer to


The RBLink is used to load firmware if you are developing applications based WICED SDK or just supply power for Duo, deliver data between Duo’s UART and the virtual comport on PC, and act as the IO extension for Duo to connect Grove accessories.

1 Like
Can't enter DFU mode
Can not get the device to go into DFU mode

Hi @guohui , similar issue here: the Duo seems to be stuck on flashing blue - listening mode, but the device will not show up on USB… I’ve tried the above steps, and the device will reboot, but only to end up in listening mode again.


I’ve brought the system into DFU mode, reinstalled the firmware, reset it, and again it will go into listening mode. Connecting thorugh

screen /dev/tty.usbmodem1421 gives me an error:
Cannot open line '/dev/tty.usbmodem1421' for R/W: Device not configured
Sorry, could not find a PTY.

What should I do?


@gerb, if you perform a factory reset with clearing stored WiFi profiles, i.e. release the setup button when RGB flashing white, it will enter the listening mode if you do not set SYSTEM_MODE(MANUAL) in your sketch. Since the default mode is set to AUTOMATIC mode, which means that Duo will trying connecting to router and then to cloud. Thus it will definitely need a valid access point to connect. As you have cleared the WiFi profiles when performing FR, so Duo enters listening mode automatically for you to config WiFi profiles.

Regarding to the usb modem issue, we haven’t met yet and hard to encount it, you can try another usb cable first, or connect your Duo to another computer for comparison.


Mine is suck on blue flashing! It was working fine, well somehow, out of the blue, it got stuck into that mode. How can I get it back to life?


Never mind, got it back to life, set the system default mode to MANUAL as guohui says.

1 Like