STM8S105K4T6C — 16 KB Flash STM8 Access Line MCU in LQFP-32 for Drone ESC, BMS, and Sensor Nodes

The STM8S105K4T6C is STMicroelectronics' mid-range Access Line 8-bit STM8 core MCU, featuring 16 KB Flash, 2 KB SRAM, 1 KB EEPROM, and 16 MHz operation in an LQFP-32 package. With 25 GPIOs, a 10-bit ADC with 7 channels, and UART/SPI/I²C interfaces, it occupies the sweet spot between the entry-level S003/S103 (8 KB) and the high-end S207 (128 KB) — providing double the Flash of the S003 plus the largest EEPROM (1 KB) of any non-Performance Line STM8, making it ideal for BLHeli_S/Bluejay ESCs with extensive configuration profiles, BMS nodes with cell-balancing history logging, and drone sensor aggregation nodes.

Part Number Decoded — Field by Field

Quick Specifications

Product Overview

The STM8S105K4T6C delivers the largest EEPROM (1 KB) in the STM8 Access Line — a standout feature for drone applications requiring extensive non-volatile storage without consuming Flash. The 1 KB EEPROM can store 8–10 complete ESC parameter profiles, months of battery cycle history, or calibration data for multiple sensors — all with 300,000 write-cycle endurance per byte, far exceeding Flash emulation approaches.

With 4× 16-bit timers (vs. 3 on the S003/S103), the S105 adds a basic timer for timebase generation or simple PWM, and the window watchdog provides enhanced system reliability monitoring — important for safety-critical BMS applications where an MCU hang must trigger a protection-FET cutoff within a defined window. The 2 KB SRAM and 16 KB Flash provide comfortable headroom for BLHeli_S/Bluejay firmware with extended features.

Key Features & Benefits

1 KB True EEPROM — Industry-Leading for 8-Bit MCU

The 1 KB (1,024 bytes) true EEPROM is the largest in any sub-$1 STM8 device — 8× larger than the S003's 128 bytes. This enables storage of: full ESC configuration sets (100 bytes × 10 profiles), battery cycle history (12 bytes/cycle × 50 cycles), factory calibration data, serial number, manufacturing date, and firmware update logs — all without consuming a single Flash page.

4× 16-Bit Timers — Extra PWM and Timebase Flexibility

The fourth timer (a basic 16-bit timer) can serve as a dedicated timebase for the BMS scheduler or generate additional PWM channels for LED brightness control — freeing the advanced and general-purpose timers for motor PWM and input capture functions without sharing.

Window Watchdog — Safety-Critical BMS Reliability

The window watchdog requires the software to refresh within a defined window (not too early, not too late) — preventing both runaway code and stuck-in-loop failures. For drone BMS applications where a hung MCU could fail to open protection FETs during an overcurrent event, this hardware safeguard is essential.

Target Applications

BLHeli_S ESC with Multi-Profile Configuration Storage

The 1 KB EEPROM stores up to 10 complete ESC configuration profiles — enabling a single ESC to instantly switch between timing/motor-timing maps optimized for different propellers, battery voltages, or flight modes. Profile selection via DShot command or startup sequence.

Smart Drone Battery BMS with History Logging

Logs battery cycle history (charge/discharge curves, capacity fade, IR growth) directly in the MCU's EEPROM over the battery's lifetime — providing cell-level health diagnostics without external memory chips. The window watchdog ensures protection FETs open within 2 ms of an overcurrent fault.

Drone Sensor Aggregation Node

Aggregates data from multiple I²C sensors (barometer, magnetometer, ambient light) and ADC inputs (battery voltage, current, temperature), performs basic filtering/calibration (stored in EEPROM), and transmits consolidated sensor frames to the flight controller via UART — offloading sensor fusion from the main FC processor.

Frequently Asked Questions

How does the STM8S105 compare to the STM8S005?

Both have 2 KB SRAM and LQFP-32 packages, but the S105 has 16 KB Flash and 1 KB EEPROM while the S005 has 32 KB Flash and only 128 bytes EEPROM. Choose the S005 if Flash size is the bottleneck (large firmware + bootloader); choose the S105 if EEPROM size matters (multi-profile configuration, battery history logging). The S105 also adds a 4th timer and window watchdog, which the S005 lacks.

Can the STM8S105 run Bluejay at 96 kHz PWM?

Yes. Bluejay firmware supports the STM8S105 target. At 96 kHz PWM, the commutation loop must complete in ~10.4 µs — within the capability of the 16 MHz STM8 core (~0.0625 µs per instruction). The 2 KB SRAM is sufficient for Bluejay's runtime data structures plus bidirectional DShot telemetry buffering at 96 kHz.

Ordering Information

Design Resources

• Datasheet (DS6116): STM8S105xx — Access Line MCU with 16–32 KB Flash, 1 KB EEPROM, AWU, and window watchdog.
• Reference Manual (RM0016): STM8S Series — Complete register-level documentation.
• Bluejay GitHub: mathiasvr/bluejay — Open-source ESC firmware supporting STM8S105 targets.
• STVD + COSMIC: Free STM8 IDE with full debug support.
• Application Note AN2860: EMC guidelines for STM8 MCUs in motor-drive environments.

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SUPERB Automation supplies genuine STMicroelectronics STM8S105K4T6C MCUs with full traceability and batch-level QA documentation. With 1 KB true EEPROM — the largest in its class — plus a window watchdog and 4 timers, the STM8S105K4T6C is the go-to MCU for drone BMS and ESC designs where non-volatile storage capacity and safety-critical reliability are paramount. Whether you need prototype quantities for ESC firmware development or production volumes for drone BMS and PDB controller manufacturing, we source through verified channels with competitive lead times. Contact us with your target quantity, delivery date, and any special packaging or marking requirements — we'll respond with a detailed quotation within 24 hours.