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AM32 ESC Unlocker

This is a tool for fast and easy unlocking of ESCs for the AM32 project.

The key benefits of using this tool over traditional debug tools are:

Unlocking a 4-in-1

Background

A lot of ESCs come with flash locked preventing updates. This is most common with BLHeli32 ESCs but may apply to others as well. In order to move these ESCs to the AM32 firmware you need to unlock them and flash a bootloader.

Note that the best option is to buy ESCs from vendors that ship with AM32, in which case you don't need this tool at all. This tool is for people who have 32 bit ESCs already that shipped with firmware other than AM32 and want to migrate to AM32.

Usage

You will need to download the linux or windows binaries for "esc_unlocker" from the releases section of this repository. Two packaged binaries are provided, one for windows and one for linux.

https://github.com/am32-firmware/AM32-unlocker/releases

When you run the tool you will get an interface like this:

Unlocker GUI

You then need to select your MCU type. If you don't know the MCU type then look at the MCU on your ESC under a magnifying glass.

You also need to select your signal pin. This is the pin on the MCU that communicates with the flight controller (ie. the DShot signal pin). This is usually PA2 or PB4.

Finding the SWD pads

You need to find the SWD pads on your ESC. Some ESCs don't have exposed SWD pads, in which case you may not be able to unlock at all.

Here is an example showing the 4 sets of SWD pads on a Foxeer 4-in-1 F421 ESC:

Foxeer 4-in-1 SWD

Note that you don't really need to identify which is SWDIO and which is SWDCLK as the process of using this tool makes it very easy to swap around when unlocking.

Connecting SWD

You will need a debug adapter. The tool supports 3 types of adapter

The simplest is to get one of the cheap stlink-v2 clones. These are available cheaply from places like ebay and aliexpress.

STLink-v2

You will need to connect the ground pin of the debug probe to ground on your ESC.

Then you should get 2 male to female dupont leads. The two female ends will connect to the SWDIO and SWDCLK pins on your debug adapter.

The two male ends should be bent slightly so that when held together they are separated by the distance between

Bent dupont pins

Unlocking Process

Choose the MCU and signal pin in the GUI, then press start. You will see the "LED" in the display go red and you will hear a rapid low beep. Attempts to flash your ESC will stream up the text box.

Now power on your ESC (preferably with no motor attached!) and then press the tips of the two dupont pins against the SWD pads. Listen for a change in sound as the tool finds the MCU. The tone will rise in pitch and the "LED" in the display will go orange if it finds your MCU. If it can't find the MCU then try the pins the other way around.

When the tool succeeds it plays a triple tone, says "Success!" and the LED goes green. Your MCU is now flashed with an AM32 bootloader. You can how use the normal AM32 config tools to load the right firmware for your ESC and change settings.

Troubleshooting

You may need to install WinUSB via zadig if you get this error:

Install from https://zadig.akeo.ie/

Diagnostics

When it doesn't work you should find a file esc_unlocker.log in the directory when you launched the unlocker. Share this file on the AM32 discord to see if someone can help.

CAUTION

It is possible that this tool could permanently brick your ESC. It isn't likely, but there are locking options in the MCUs that are not reversible. If the wrong options are set then you will not be able to recover your ESC, even with a soldered SWD connection. Use at own risk.