Security researcher Jessie Chab targeted a children's drawing robot for a hardware hack. The device reads barcodes on cards to produce pre-defined drawings. After dissecting the toy, Chab identified key components including an ARM Cortex-M0 MCU and NOR flash memory, setting a goal to enumerate all hidden drawings and add custom ones.
The breakthrough came through analyzing the optical sensor's multiplexing scheme. Using a logic analyzer, Chab mapped how the board powers sensor groups in alternating cycles to read an 8-bit barcode. This revealed the machine was announcing unlisted images like "Take a bath!" during fuzzing tests, hinting at undocumented functionality.
With the protocol understood, the researcher emulated barcodes using a Raspberry Pi's GPIO pins. By scripting binary values to simulate card scans, the project moved from reverse-engineering to active manipulation. This approach demonstrates how simple toys can hide complex, hackable systems behind their cute exteriors.
Source: Hacker News: Front Page · Summarized by HeadlinesBriefing