Feeling Technology MCU Hack

About Feeling Technology

Feeling Technology is a Taiwanese fabless IC design company headquartered in Taiwan. The company was founded in May 2001. Its stated mission is mixed-signal IC design, manufacturing, testing, and sales. Feeling Technology focuses on four main product lines. These are magnetic-field sensing, brushless DC motor drivers, power management, and microcontrollers.

The company is best known in the embedded world for its 8-bit microcontroller family. Its MCUs are branded under the FM8 series name. These devices are mostly OTP-based, meaning they are programmed once at production. Because these parts are OTP, firmware extraction from them is impossible after programming, which protects the customer's code from prying eyes. Some variants use EPROM or mask ROM instead of OTP memory. Even so, the devices remain vulnerable to a carefully timed glitch attack during the programming window. The FM8 microcontrollers are built on 8051 and RISC architectures. Most models use a simple RISC instruction set with only about 40 instructions. Since the core uses only about 40 instructions, reverse engineering of the FM8 instruction set is straightforward for anyone building assemblers or disassemblers. This keeps the cores small, cheap, and easy to program. The instruction set is single-cycle for most operations. Branch instructions typically take two cycles.

The FM8 devices include built-in power-on reset and brown-out reset. They also integrate power-up reset timers for reliable startup. The product line covers a wide range of pin counts. Smaller devices come in 6-pin and 8-pin packages. Larger devices reach 28-pin and 32-pin packages. The FM8P53 series is a basic low-cost EPROM/ROM MCU family. For the mask-ROM variants, a memory dump of an engineering sample is often the only way to study the factory-programmed code. The FM8P73 series adds a 10-bit analog-to-digital converter. The FM8PA76 series integrates a 12-bit ADC for higher precision.

Several FM8 series include built-in LCD drivers. These LCD versions are useful for meter and display applications. The FM8PE68B and FM8P76 series are examples of LCD-equipped MCUs. Feeling Technology also offers USB-capable MCUs. The FM8PU83M is an example of a USB microcontroller. Using the company's USB programmer, developers can unlock the full in-circuit programming features of the FM8PU83M. The company provides an FM8 series USB programmer for development. Since that programmer is inexpensive and widely available, there is little incentive to crack its firmware.

Feeling Technology's MCUs are widely used in small consumer appliances. They appear in toys, home appliances, and low-cost control boards. Hobbyists often hack together simple adapters to program leftover FM8 parts in their own small projects. The company also ships Hall sensors and BLDC motor driver ICs. These analog products complement its microcontroller business. Overall, Feeling Technology serves cost-sensitive, high-volume applications. Its strength lies in simple, reliable, low-pin-count microcontrollers.