BP35A1 - 920MHz Wi-SUN Module with 32-bit MCU | ROHM

Smart Electricity Meter B-Route Communication

In Japan's smart electricity meter infrastructure, the Home Area Network (HAN) B-route link between the utility meter and in-home equipment uses the Wi-SUN B-route profile in the 920MHz band. The BP35A1 fits this role directly: its integrated Wi-SUN B-route firmware removes the need to license or develop the protocol stack, its -103dBm typical sensitivity at 100kbps (BER < 0.1%) sustains reliable links through residential walls, and its Wi-SUN Alliance certification (WSA0064, HAN single-hop, ECHONET profile) satisfies interoperability requirements for connecting to utility meters. Because the module is a plug-in connector joint type part with built-in antenna, meter-adjacent equipment can be assembled without RF soldering processes, and the radio function can be swapped in the field without reworking the host board. Designers should verify connector keep-out zones against ROHM's layout guidance to preserve antenna performance.

Home Energy Management System (HEMS) Controllers

HEMS controllers aggregate consumption data from smart meters and control in-home devices. The BP35A1 is Wi-SUN Alliance certified as product WSA0064 specifically in the HEMS Controller, HAN (Single-Hop HAN) role, making it a certification-ready radio subsystem for these products. The integrated 32-bit microcontroller executes the Wi-SUN stack on-module, so the host processor only handles application logic over a simple serial interface, reducing host firmware complexity and memory footprint. The 920MHz sub-GHz band with -103dBm sensitivity provides whole-home coverage including through-wall paths that defeat 2.4GHz radios, and the built-in antenna keeps the HEMS enclosure design free of external antenna apertures. Using the connector joint type mounting, manufacturers can pre-certify the radio assembly separately from the HEMS main board, shortening overall product certification cycles.

Building and Facility Energy Monitoring

Commercial building energy monitoring gateways benefit from the BP35A1's sub-GHz mesh characteristics. The 920MHz band propagates through concrete and equipment racks better than 2.4GHz, and the -103dBm typical receive sensitivity at 100kbps (BER < 0.1%) extends link margin for sensors distributed across floors and mechanical rooms. Because the module ships with integrated Wi-SUN firmware, system integrators can deploy multi-node Wi-SUN networks without RF engineering staff, treating each BP35A1 as a certified communication port. The connector joint type interface allows radio modules to be installed as field-serviceable cartridges in gateway housings, and the built-in antenna removes external whip-antenna cost and enclosure sealing complexity. For monitoring dashboards, the 100kbps class data rate is ample for metering telemetry, which is inherently low-bandwidth but latency- and reliability-sensitive.

Sub-GHz Mesh Sensor Networks

For private sensor networks in the 920MHz band - environmental monitoring, agricultural telemetry, asset tracking - the BP35A1 provides an integrated, pre-certified Wi-SUN node in one plug-in unit. The on-module 32-bit microcontroller runs both the Wi-SUN mesh stack and headroom for application-level tasks, so a simple host MCU or even no separate host for basic nodes can suffice. Sensitivity of -103dBm typical at 100kbps with BER below 0.1% supports long-range, low-power links, and Wi-SUN mesh routing adds path diversity in obstructed sites. The built-in antenna makes IP-sealed outdoor sensor enclosures straightforward since no antenna connector or feedthrough is required. Developers should prototype host interfacing on the BP35A7A 2.54mm conversion adapter before committing to a custom carrier, verifying current consumption and range against their deployment topology.

Smart Gas and Water Metering Infrastructure

Gas and water utilities use the same Wi-SUN 920MHz HAN architecture as electric metering for neighborhood-area data collection. The BP35A1's specified low-power radio design targets exactly this class of application: certified Wi-SUN B-route operation, integrated 32-bit microcontroller with Wi-SUN firmware, and -103dBm typical sensitivity at 100kbps (BER < 0.1%) for robust links from pit or basement locations. The connector joint type package with built-in antenna suits meter enclosures where reflow soldering of RF parts is undesirable and where modules may be replaced during service intervals. Because the module is the same certified part used in electric-meter B-route designs (WSA0064, single-hop HAN, ECHONET profile), utility integrators can reuse firmware and test infrastructure across meter families, reducing qualification cost per deployment.

Wireless Module Evaluation and prototyping

Before committing a production host PCB, engineers evaluate the BP35A1 on ROHM's dedicated BP35A7A conversion adapter board, which provides a 2.54mm-pitch breakout of the module's connector joint type interface for breadboards and logic analyzers. This workflow validates the host serial interface, power supply behavior across transmit bursts, and antenna keep-out effects early in the project. The integrated Wi-SUN firmware means evaluation can proceed at the application layer immediately - issuing connection commands and exchanging ECHONET-profile data - rather than first porting a radio stack. Because the BP35A1 is plug-in, the same module can move between the evaluation adapter and custom carrier boards, protecting certified hardware during iterative host revisions. Teams should benchmark current consumption and link margin at the target data rate of 100kbps during this phase.