/efm8-unbricker

Unbrick EFM8UB3 Thunderboard development board using an Arduino

Primary LanguageC++MIT LicenseMIT

Unbrick EFM8UB3 Thunderboard development board using an Arduino

The EFM8UB3 Thunderboard development board from Silicon Labs has a strange failure mode where you can get it into a state where the on-board JLink debugger can no longer reset the MCU. This makes it look like you've totally bricked the board. But you haven't!

You can use an Arduino to drive the C2 programming interface pins on the Thunderboard to recover to a state where the on-board debugger can talk to the MCU again.

This is all explained in more detail in a blog article.

This repository comes in two parts:

The unbricker

This is a simple Arduino sketch in the unbricker directory. It uses code from https://github.com/conorpp/efm8-arduino-programmer for all the C2 programming interface communication. It's written to use an Arduino MKR WiFi 1010, because that's what I had lying around, but you can adapt it to use more or less any Arduino board, just by changing the pin numbers used for the C2D data and C2CK clock signals.

To use it:

  1. Connect the Thunderboard and Arduino together on a breadboard. You want to wire things up things up like this:
Arduino Thunderboard  
GND GND
VCC 3V3
Digital pin 0 P2.0 C2D data connection
Digital pin 1 RST C2CK clock connection

  1. Make sure the "Power Source" selection switch on your Thunderboard is set to "DBG USB".

  2. Connect the Arduino to your PC and flash the unbricker.ino sketch onto it.

  3. Start the serial monitor from the Arduino IDE.

  4. Send an "unbrick" command to the Arduino over the serial monitor.

That's it! If it works, you should be able to disconnect your Thunderboard from the Arduino, connect a USB cable to the Thunderboard's JLink USB port and talk to it again using JLink Commander or whatever other programming software you use.

A demonstration brick-it program

You probably don't want to run this. I wrote it to test that the unbricker works reliably. It's a small C program made to be compiled with SDCC that misconfigures the clocks on the EFM8UB3 in a way that prevents the Thunderboard's JLink debugger from communicating with the MCU.

Really, you probably don't want to run it. I'm not even going to write any instructions here...