We’re pleased to announce the release of BleuIO Pro firmware v1.0.7.3, introducing new MTU negotiation commands, improved GATT discovery stability, and optimized handling of complex Bluetooth Low Energy (BLE) devices.

This update gives developers greater control over BLE connections while improving performance and reliability when working with peripherals containing large GATT databases.

New MTU Negotiation Controls

Firmware v1.0.7.3 introduces two new AT commands for managing MTU negotiation.

AT+REQMTU – Request MTU Exchange Manually

The new AT+REQMTU command allows developers to initiate a GATT client MTU exchange at any point after establishing a BLE connection.

This provides greater flexibility when testing peripheral behavior, debugging connections, or managing specific connection workflows.

AT+AUTOMTU – Control Automatic MTU Negotiation

The new AT+AUTOMTU command lets developers enable or disable automatic MTU negotiation during connection parameter updates.

• AT+AUTOMTU=1 – Enable automatic MTU negotiation.
• AT+AUTOMTU=0 – Disable automatic MTU negotiation.

When disabled, developers can use AT+REQMTU to trigger the exchange manually, allowing more predictable connection handling in automated scripts and applications.

Improved GATT Discovery Stability

This release addresses an issue where BleuIO Pro could unexpectedly reset while discovering services and characteristics on peripherals with exceptionally large GATT databases.

The discovery engine has been redesigned to use a sequential streaming architecture instead of memory-intensive hierarchical caching.

With this improvement, GATT attributes are processed dynamically and sent to the USB interface as they are discovered.

Key benefits include:

• Reduced memory consumption during GATT discovery.
• Improved connection stability with complex BLE peripherals.
• Support for up to 165 characteristics within a single service.
• More efficient processing of large GATT profiles.

These improvements apply to the following commands:

• AT+GETSERVICES
• AT+GETSERVICESONLY
• AT+GETSERVICEDETAILS

GATT Discovery Output Changes

With the new streaming architecture, discovered GATT attributes are reported immediately as they are processed.

One small change affects the presentation order of descriptors. Previously, descriptors such as CCCDs (0x2902) appeared directly after their associated characteristics. They are now grouped at the end of the corresponding service block.

Important: All JSON fields in verbose mode and standard text-mode output strings remain unchanged. Only the order of descriptor entries has been modified.

Developers using custom parsers that depend on descriptor ordering should review their implementation to ensure compatibility.

How to Update Your Firmware

Updating your BleuIO Pro is straightforward.

You can download the latest firmware and follow the step-by-step update instructions in our official documentation:

BleuIO Pro Firmware Update Guide

Alternatively, you can update directly from your browser using the BleuIO web application:

Update Firmware Using BleuIO Web App

Both methods provide a simple way to get your BleuIO Pro running the latest firmware.

We recommend updating to v1.0.7.3 to benefit from the latest MTU controls, improved GATT discovery stability, and support for larger peripheral profiles.