OBS421 - Dual-mode Bluetooth module for classic Bluetooth and Bluetooth Low Energy (BLE) applications

The powerful stand-alone Bluetooth module OBS421 is a dual-mode (Bluetooth Smart Ready) module complete with embedded Bluetooth stack and serial port application.

The powerful stand-alone Bluetooth module OBS421 is a dual-mode (Bluetooth Smart Ready) module complete with embedded Bluetooth stack and serial port application. The OBS421 features a UART interface for transparent serial data transmissions. It can be used as a Bluetooth Smart Ready client for any host and it can access any Bluetooth Smart device that implements services based on the Generic Attribute Profile(GATT), such as a low energy battery service or an automation I/O service.

The OBS421 can also be used in applications where a smartphone, tablet or laptop is to connect to a serial device such as a Programmable Logic Controller (PLC).

Customers may embed their own applications, eliminating the need of an external application processor, thus saving considerably on the bill of material and PCB space. The middleware with easy-to-use interfaces speeds up and simplifies application development. Customer developed applications can make use of the additional module interfaces, such as GPIO, SPI, I2C, JTAG, and UART / USART and analog inputs.

The module is fully Bluetooth qualified and provides modular radio type approvals for the US, Europe, Japan and Canada (FCC, R&TTE, MIC, IC). The OBS421 is also compliant with EMC, Safety and Medical standards.

The robust module is easily configured via AT commands as well as cover a range of 300 meters, throughput up to 1.3 Mbps and operating temperatures of -30°C to +85° C.


  • Bluetooth v4.0 with Bluetooth low energy and Classic Bluetooth (Bluetooth Smart Ready)
  • Embedded stack (SPP, DUN, PAN, GATT)
  • Cortex M3 MCU for customer developed applications
  • u-blox Low Energy Serial Port ServiceBluetooth_Smart_Ready_120px
  • High throughput of 1.3 Mbps
  • Advanced multipoint capability with 7 slaves
  • Apple iOS and Google Android connectivity

For sales and technical development support from our in-house engineering team, please contact the Alpha Micro team.

Parameters Specifications

v4.0 (Bluetooth low energy and Bluetooth BR/ EDR)


250m, internal antenna

300m, external antenna

Output power

11 dBm, internal antenna

13 dBm, external antenna


1.3 Mbps (Bluetooth BR/EDR)

iAP2 throughput 1 Mbps
Microprocessor 72 MHz, ARM 32-bit Cortex M3 processor capacity with 64 kB RAM and 384 kB flash
Electrical data
RF power supply 3.0 to 6.0VDC
Power consumption

0.6 mA @ 3.0 V (min.)

44 mA @ 3.0 V (average Tx)

Software features
Embedded software

u-blox dual mode Bluetooth stack

Serial port application

Bluetooth profiles

u-blox Low Energy Serial Port Service

Generic Attribute Profile (GATT)

Serial Port Profile (SPP)

Dial-up networking Profile (DUN GW, DUN DT)

Personal Area Networking Profile (PAN) roles: PANU & NAP

Profile roles Central Role, Peripheral Role
Max. number of slaves

7 Bluetooth BR/EDR & Bluetooth low energy

Configuration tools

AT commands via Bluetooth or serial port

Serial Port Toolbox (Windows-based SW)

Low Emission Mode®

Prevent disrupting other 2.4GHz radios

Wireless Multidrop™

For simultaneous connections to Bluetooth low energy and Bluetooth BR/EDR devices

Extended Data Mode™ Individually controlled multipoint data channels
Quality of Service (QoS) Yes
Repeater functionality Extended range
Security Simple Pairing
iAP + iAP2 High speed iOS connectivity with Bluetooth BR/EDR connections
UART Logic level
RS232/422/485 (option via external transceiver)
Baud rate

Max 1.5 Mbit/s Support for non-standard baud rates

Flow control CTS/RTS (hardware) or none
GPIO pins 9
U.FL antenna connector (external antenna version only)



16.0 x 36.0 x 3.2 mm (internal antenna)

16.0 x 36.0 x 2.6 mm (external antenna)




Mounting holes

Machine mountable

Board-to-board connector

Solder land pads

Environmental data, quality & reliability

Operating temperature -30°C to +85°C
Certifications and approvals
Type approvals

Europe (ETSI R&TTE)

US (FCC/CFR 47 part 15 unlicensed modular transmitter approval)

Canada (IC RSS)

Japan (MIC - formerly TELEC)

R&TTE Directive 1999/5/EC

Effective use of frequency spectrum: EN 300 328

EMC: EN 301 489-1, EN 301 489-17, EN 61000-6-2

Health and safety: EN 62479, EN 60950-1, IEC 60950-1

Medical Electrical Equipment IEC 60601-1-2
Bluetooth Qualification



Click here for the u-blox short range radio modules linecard (PDF).

Part No. Description Pack Size
CB-OBS421I-24 OBS421 module (Rev. B) with on-board antenna, supports Apple iOS connections (Bluetooth Low Energy only). Reel of 250
CB-OBS421X-24 OBS421 module (Rev. B) with U.FL connector for external antenna, supports Apple iOS connections (Bluetooth Low Energy only) Reel of 250
Support Products
CB-OBS421I-26 EVK-OBS421: Includes OBS421i-24 module with additional JST connector, USB module adapter (installs virtual COM-port), USB extension cable, JST to flying leads cable, configuration SW. Each
CB-WDK-12-A SDK for customer developed applications, platform development board ACC-56, OBS421i-24/x-24 modules with additional JST connector, external antenna, USB module adapter ACC-34. Support not included. SLA must be signed. Each
Modules with iAP support for Classic Bluetooth connections to Apple iOS devices*
CB-OBS421I-I4 OBS421 module with iAP support and on-board antenna Reel of 250
CB-OBS421X-I4 OBS421 module with iAP support and U'FL connector for external antenna Reel of 250

* All current OBS421 module versions support Apple iOS connections via Bluetooth low energy. Classic Bluetooth connections are supported only by OBS421 versions with iAP support, but other special requirements also apply, see http://tinyurl.com/ndk6vj2.

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Last updated: 21 June 2017