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TC420 Null Mode Error Fix

TC420 Null Mode Error Fix

A lot of people have been contacting me all with the same problem. The symptoms are:

  • You plug in the TC420 via USB
  • You upload the mode(s) and test the mode(s) with the play button in the PLed software and it works fine
  • You disconnect the USB but the mode(S) does not run, no lights come on
  • If you switch the power off then on, the mode(s) disappear and NULL is displayed on the screen

The problem has been caused by an error when programming the micro-controller inside the TC420. In the coming weeks I hope to have a couple of fix options, but at the moment the only fix I can give is via the manufacturer. Hopefully soon there will be a fix you can perform with a Raspberry Pi

Manufacturer Fix

PLEASE NOTE: You may have trouble getting an adapter due to the high demand for them.

To fix the problem, you will need to contact the manufacturer and order a Nuvoton Debug Adapter which will update your device. The programming issue has also caused a problem with updating firmware in the standard way, so you need to buy this device. Use the contact details below to order the device.

Wendy Cai | Sales Manager | World Uniqueen Co..,Ltd
Skype: cailihappy919 | E: superled@worlduniqueen.com
2902# Dynamic World Futian District Shenzhen China 518031
M: (86) 15999625931 | T:(86) 755-83266775

www.worlduniqueen.com | Ali: http://uniqueen.en.alibaba.com

Implementing the fix

Make sure that the TC420 is disconnected from all power sources before attempting this fix.

The Nuvoton Debug Adapter has a USB connector on one side and an SWD connector on the other for programming microprocessors. The adapter is pre-programmed with the firmware for the TC420 without any additional software or drivers.

You will need to take the top off the TC420 to access the circuit board and locate the SWD connector (circled in red).

Connect the SWD connector on the adapter to the SWD socket on TC420 making sure to orientate the cable correctly. Then plug the USB jack of the adaptor in somewhere just to provide power to the adapter and the TC420. Once it is connected, you press the ‘Off-Line’ button on the adaptor to flash the firmware.

Your TC420 should now be fixed and can be re-assembled.


Thanks to Brian who provided this solution and the images. Hopefully this will help you get up and running.