Since FNIRSI likely uses the same unprotected firmware across batches, a bad actor could pre-flash modified units at the factory or during distribution.
To understand the DSO-TC2’s firmware, one must first acknowledge its ancestry. The component tester functionality is clearly derived from the famous open-source AVR-Transistortester project by Markus Frejek and Karl-Heinz Kübbeler. This project, originally designed for 8-bit AVR microcontrollers, provides automatic identification and characterization of resistors, capacitors, diodes, transistors, and even thyristors. Fnirsi’s engineers ported this logic to the STM32 platform, wrapping it in a more modern graphical interface.
This open-source foundation explains both the strengths and weaknesses of the tester side. The firmware reliably identifies thousands of components, measures parameters like hFE (transistor gain) and Vf (diode forward voltage), and displays pinouts—all within seconds. However, the legacy code also introduces peculiarities: the tester can be confused by very low-value resistors or high-capacitance capacitors, and it occasionally misidentifies complex components like JFETs. The firmware does not improve upon the open-source algorithms; it merely repackages them. In this sense, the DSO-TC2’s firmware is a compilation rather than a creation—a pragmatic choice that keeps development costs near zero.
[1] FNIRSI. (2022). DSO-TC2 User Manual.
[2] STMicroelectronics. (2019). STM32F405/415 Reference Manual.
[3] Winbond. (2018). W25Q16JV Datasheet.
[4] Reverse Engineering STM32 Firmware, Embedded Lab, 2021.
[5] “FNIRSI DSO-TC2 Teardown,” EEVblog Forum, 2023. fnirsi dso-tc2 firmware
Note: This paper is a template. Actual addresses, offsets, and exact MCU variant depend on your specific DSO-TC2 hardware revision. Always verify before attempting reflashing.
In the realm of affordable electronic test equipment, the Fnirsi DSO-TC2 occupies a unique niche. It is a hybrid device—part digital storage oscilloscope (DSO), part component tester—packaged in a colorful, handheld shell. While its hardware (a 2.8-inch IPS display, a 2.4G wireless probe, and an STM32-based core) grabs attention, it is the firmware that truly defines the device. The DSO-TC2’s firmware is a study in contrasts: it is surprisingly capable for its price point, yet frustratingly limited for serious work; it is functional enough for hobbyists, but riddled with the legacy of open-source projects and closed-source constraints. This essay argues that the firmware of the DSO-TC2 is both the device’s greatest asset and its most significant bottleneck, representing the delicate balance between accessibility, cost, and performance in the modern maker economy.
The internal firmware starts with the STM32 vector table at 0x08000000. The reset handler points to code that initializes clocks, then configures GPIO for the frontend. Since FNIRSI likely uses the same unprotected firmware
Strings extracted (strings internal_firmware.bin):
DSO-TC2 V1.2
CALIB_DATA
TP_LOW=150
TP_HIGH=2750
Component Tester Mode
ADC overflow
The DSO-TC2 is a 2-in-1 oscilloscope (200 kHz bandwidth) + transistor tester. Its firmware is closed-source and updated via a .upd file using a Windows PC tool (no OTA or macOS/Linux native support).
Where the component tester excels, the oscilloscope firmware reveals the device’s cost-cutting nature. The DSO-TC2 is marketed as a 2.5 MHz analog bandwidth scope with a 10 MSa/s sampling rate—adequate for audio frequencies and basic microcontroller debugging (e.g., checking PWM signals or I2C clock lines). The firmware manages the STM32’s ADC (analog-to-digital converter) and DMA (direct memory access) to capture waveforms, then renders them on the display. Note: This paper is a template
However, the firmware’s limitations become apparent upon deeper use:
These are not hardware limitations alone; they are deliberate firmware simplifications. The STM32F103 (or similar) inside the DSO-TC2 has enough power to implement basic digital triggering and averaging, but Fnirsi chose not to invest in the firmware development. Instead, the oscilloscope mode feels like a proof-of-concept—enough to claim “oscilloscope” on the box, but not enough for serious debugging.