NXT ticks quietly and has a blank display

If you have a Lego Mindstorms NXT brick which has started to tick quietly, and does absolutely nothing else, then it has gone into "firmware update" mode.

Strangely, there is absolutely nothing you can do to rescue it from this mode, other than updating its firmware. Once in this mode, there is no way to cancel it on the brick itself.

(To get it into this mode, you have to insert a thin object such as a toothpick or a straightened paper-clip into the mounting hole on the base which is immediately underneath the USB port. There is a push switch inside there, and it puts the brick irrevocably into firmware update mode. Given that NXT bricks are frequently given to children in robotics classes at school, this is not an unusual thing to get done to them.)

The solution is quite simple: re-install the firmware.

There are many guides on the Internet showing how to do this under Windows. The basic summary is:

  1. Install Lego's NXT software on your Windows computer, along with the necessary USB driver
  2. Connect the NXT brick to the computer by USB
  3. In the software, select Tools and Update NXT Firmware

If you use Linux instead, you need the fwflash utility (which on Debian / Devuan / Ubuntu is in the libnxt package (Jessie or later)).

Download a firmware file for your NXT brick, plug it in by USB and use the following command (as root) to install the firmware: 

# fwflash "LEGO MINDSTORMS NXT Firmware V1.31.rfw"
Checking firmware... OK.
NXT device in reset mode located and opened.
Starting firmware flash procedure now...
Firmware flash complete.
New firmware started!

Replace the filename with whichever firmware file you wish to install. Installing / updating the firmware takes about 15 seconds (the brick continues ticking during this time), and the brick will restart at the end of the process.

If fwflash gives you the message: 

Checking firmware... OK.
Error while connecting to NXT: Error trying to configure the NXT USB link

Then you probably have a conflict with the cdc_acm kernel module. Check dmesg or syslog to see whether connecting the brick by USB produced messages like: 

cdc_acm 4-2:1.0: This device cannot do calls on its own. It is not a modem.
cdc_acm 4-2:1.0: ttyACM0: USB ACM device
usbcore: registered new interface driver cdc_acm
cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters

If it did, the workaround is simple: run rmmod cdc_acm after connecting the brick to USB and before uploading the firmware: 

Connect the NXT brick to USB
# rmmod cdc_acm
# fwflash "LEGO MINDSTORMS NXT Firmware V1.31.rfw"

Have fun with the now-working NXT brick :)

I've lost track of the number of NXT bricks I've bought on eBay for very good prices, simply because the sellers didn't know what the ticking sound meant, or because other buyers don't know what to do about it. I've never bought a ticking brick which turned out to have some other fault as well, once I'd installed the firmware.

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