A tiny Bluetooth module comes with pre-loaded firmware, allowing engineers to add wireless connectivity through simple UART commands.
KAGA FEI has introduced the ES4L15MA1, a Bluetooth Low Energy 6.0 module measuring just 8.55 × 3.25 × 1.00 mm, designed for compact, battery-powered products such as smart locks, lighting, fitness trackers, wearables and industrial sensors. Built around Nordic Semiconductor’s nRF54L15 wireless microcontroller, it is accompanied by the larger EC4L15MA1, which measures 12.9 × 9.6 × 2.0 mm.
The hardware builds on KAGA FEI’s earlier ES4L15BA1, but the new module changes the development approach by shipping with firmware already loaded. Instead of developing the Bluetooth application firmware from scratch, a host processor can communicate with the module through a command-based API over UART while the module manages the Bluetooth functions.
Its embedded software supports both Peripheral and Central roles and can maintain connections with up to eight BLE devices. Developers can configure custom Generic Attribute Profile services, while an SPP-like Bluetooth LE service provides a simpler way to transfer data. Firmware updates are supported through both over-the-air and UART device firmware update, while Power Save and Deep Sleep modes target battery-powered applications.
Inside the compact module, the nRF54L15 combines a 128 MHz Arm Cortex-M33 processor with a RISC-V coprocessor for software-defined peripherals. It provides 256 KB of SRAM and 1.5 MB of non-volatile memory, while the radio supports output power up to +8 dBm across the 2.4 GHz band and Bluetooth data rates from 125 kbit/s to 2 Mbps. The module provides five GPIOs, a 14-bit analogue-to-digital converter and a global real-time clock. It operates from 1.7 to 3.6 V across -40°C to 105°C and uses Arm TrustZone hardware isolation for security.
The nRF54L15 also includes capabilities beyond the Bluetooth functions exposed through the module’s ready-to-use firmware, including an 802.15.4 radio for technologies such as Thread, Zigbee and Matter, as well as a proprietary 2.4 GHz mode supporting data rates up to 4 Mbps. KAGA FEI also lists Bluetooth 6.0 features such as direction finding and Channel Sounding among the capabilities of the underlying SoC, but its public ES4L15MA1 documentation does not clearly confirm Channel Sounding as part of the shipping firmware.
While the larger EC4L15MA1 is already in mass production, KAGA FEI plans to provide ES4L15MA1 samples in January 2027 and begin mass production in February 2027. Pricing has not been announced. An evaluation board is available for development work, while KAGA FEI lists radio certifications for Japan, the US and Canada and provides an ETSI EN 300 328 v2.2.2 conducted test report.
For Indian product teams, the module’s overseas certifications do not by themselves establish approval for use in India. Wireless modules operating in India’s licence-exempt bands may require Wireless Planning and Coordination Equipment Type Approval , subject to the applicable rules and exemptions. KAGA FEI does not list an India-specific WPC approval for the ES4L15MA1, so manufacturers planning to use it in Indian products would need to check the applicable approval requirements before deployment.
KAGA FEI’s approach isn’t the only way manufacturers are addressing the nRF54L15’s small form factor. Some competing modules on the same chip prioritize integrated antenna design, while KAGA FEI’s ES4L15MA1 focuses on pre-loaded firmware to reduce development time. For product engineers, the distinction is increasingly less about the wireless silicon itself and more about how much development work is required before that silicon can become part of a finished product.
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