Most of us will probably have seen Nintendo’s latest gadget pop up recently. Rather than a Switch 2 announcement, we got greeted with a Nintendo-branded alarm clock. Featuring a 2.8″ color LCD and a range of sensors, it can detect and respond to a user, and even work as an alarm clock for the low, low price of €99. All of which takes the form of Nintendo-themed characters alongside some mini-games. Naturally this has led people like [Gary] to buy one to see just how hackable these alarm clocks are.

As can be expected from a ‘smart’ alarm clock it has 2.4 GHz WiFi connectivity for firmware and content download, as well as a 24 GHz millimeter wave presence sensor. Before [Gary] even had received his Alarmo, others had already torn into their unit, uncovering the main MCU (STM32H730ZBI6) alongside a 4 GB eMMC IC, as well as the MCU’s SWD pads on the PCB. This gave [Gary] a quick start with reverse-engineering, though of course the MCU was protected (readout protection, or RDP) against firmware dumps, but the main firmware could be dumped from the eMMC without issues.

After this [Gary] had a heap of fun decrypting the firmware, which seems to always get loaded into the external octal SPI RAM before execution, as per the boot sequence (see featured image). This boot sequence offers a few possibilities for inserting one’s own (properly signed) contents. As it turns out via the USB route arbitrary firmware binaries can be loaded, which provided a backdoor to defeat RDP. Unfortunately the MCU is further locked down with Secure Access Mode, which prevents dumping the firmware again.

So far firmware updates for the Alarmo have not nailed shut the USB backdoor, making further reverse-engineering quite easy for the time being. If you too wish to hack your Alarmo and maybe add some feline charm, you can check [Gary]’s GitHub project.