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Use UART and Bluetooth Low Energy with AS-611Bn

AS-611Bn exchanges lowercase ASCII commands and fixed-format sensor frames over 3.3 V TTL UART or a BLE GATT interface documented as Nordic UART Service (NUS).

note

Firmware compatibility This page follows the supplied manual marked Ver.4.0 Jun.2026. The command terminator is unspecified; obtain the correct line ending for the installed firmware before transmitting commands.

UART settings​

ParameterValue
Signal level3.3 V TTL
Default baud rate460800 bps
Supported baud rates115200, 230400, 460800, 921600 bps
Data bits8
ParityNone
Stop bits1
Flow controlNone
Command encodingASCII, lowercase commands
warning

Logic level 3.3 V TTL UART is not RS-232. Use a compatible adapter and a common ground.

Change the UART baud rate​

baud 115200

The manual says the setting is saved, then the module reboots. Reopen the host port at the new rate. If using BLE, reconnect after the reboot.

Baud-rate change followed by module reboot and host reconnection
Example for baud 115200: reopen UART at 115200 bps after reboot, or reconnect BLE and enable notifications. Other settings may pause output without rebooting. View full-size image.

BLE identity​

The supplied manual says:

  • Bluetooth 4.0 or later is supported.
  • The advertising name is AS_611B.
  • The profile uses the Nordic UART Service.

GATT UUIDs​

RoleUUID
Nordic UART Service6E400001-B5A3-F393-E0A9-E50E24DCCA9E
TX characteristic6E400003-B5A3-F393-E0A9-E50E24DCCA9E
RX characteristic6E400002-B5A3-F393-E0A9-E50E24DCCA9E

These UUIDs match Nordic's NUS definition. In NUS, TX/RX are named from the peripheral's perspective: the client writes commands to RX (…0002) and subscribes to notifications from TX (…0003). Discover the actual AS-611Bn characteristic properties and permissions before selecting write and notification operations. The manual does not specify its negotiated MTU, fragmentation rules, pairing, bonding, or encryption requirements.

Test with a mobile application​

  1. Power the AS-611Bn.
  2. Open a BLE scanner or NUS-compatible terminal.
  3. Find the approved advertising name.
  4. Connect to the NUS service.
  5. Enable notifications on the module-to-client characteristic.
  6. Write a supported lowercase command, such as stop or start, with the firmware-confirmed terminator to RX. Choose the write procedure supported by its discovered properties.
  7. Confirm that complete ASCII frames are received.

The supplied manual suggests the UART utility in nRF Toolbox. Use an NUS-compatible client that exposes the required characteristics and notification controls.

Illustrative BLE scan, Nordic UART Service and command exchange
BLE client mockup, not an application capture. Send lowercase mode 1, not the uppercase MODE 1 shown in the artwork. Write to NUS RX and subscribe to TX notifications. View full-size image.

Integration rules​

  • Parse the stream by start and end markers, not by assuming one BLE packet equals one frame.
  • Buffer partial frames and handle multiple frames in one notification or UART read.
  • Accept the shorter no-target frames.
  • A baud change is documented to reboot the module; reconnect after that reboot. For other settings, monitor the connection rather than assuming every reconfiguration disconnects BLE.
  • Record malformed or unknown frames instead of silently treating them as measurements.

Reconfiguration behavior​

The manual is inconsistent: its protocol section distinguishes a temporary output pause from a baud-triggered reboot, while the Bluetooth section broadly describes a reboot after changing settings. The exact behavior of each command remains firmware-dependent. After an actual disconnect, reconnect, rediscover the service if needed, re-enable notifications, and establish the current mode before parsing measurements.

Official references​

Next steps​