<![CDATA[How to set MTU for BLEUARTClient]]>Hello, I am trying to receive data on a Core2 that I am sending from an Atom S3 Lite.

On the S3, I send the data via BLE server with a simple ‘write’ and I can read the data on a smartphone.

When I establish a connection on the Core2 as a BLE client, the connection works, but with ‘read’ I only get the first 20 characters of the sent data.

This is probably normal for BLE connections, but I get the full length on the smartphone, so sending is not the problem. Normally, you can set an MTU on the receiving side. However, the ‘set_mtu’ command does not seem to exist on the Core2.

The ‘new’ library contains this ‘set_mtu’ command.

HOW can you set the MTU on the Core2 BLE client?

]]>https://community.m5stack.com/topic/7899/how-to-set-mtu-for-bleuartclientRSS for NodeWed, 29 Apr 2026 06:43:00 GMTTue, 18 Nov 2025 09:32:52 GMT60<![CDATA[Reply to How to set MTU for BLEUARTClient on Fri, 21 Nov 2025 09:31:04 GMT]]>After many try and more than many errors .. I´m able to reveive 256 bytes instead of 20 .. but in these 256 bytes are only 20 byte long pieces of the original message.

Send thee lines like "ab<30 characters long>/r/n"

Receive 60 bytes like "ab..<only first 20 bytes>ab..<only first 20 bytes>ab..<only first 20 bytes>"

And my Smartphone receives the full sent characters seperated like "ab<30 characters long>/r/n", "ab<30 characters long>/r/n", "ab<30 characters long>/r/n"

I ended now up with chunking my message into 20 byte pieces before sending and putting the message together after receiving.

]]>https://community.m5stack.com/post/30219https://community.m5stack.com/post/30219Fri, 21 Nov 2025 09:31:04 GMT<![CDATA[Reply to How to set MTU for BLEUARTClient on Tue, 18 Nov 2025 10:22:31 GMT]]>Btw:

The BLE server can send and receive long messages.

The BLE client can send long messages, but has this limitation for received messages.

]]>https://community.m5stack.com/post/30202https://community.m5stack.com/post/30202Tue, 18 Nov 2025 10:22:31 GMT<![CDATA[Reply to How to set MTU for BLEUARTClient on Tue, 18 Nov 2025 10:07:27 GMT]]>I have now tested the ‘new’ BLE Brick, and although it has an MTU command, the following error occurs:

Traceback (most recent call last):
File ‘<stdin>’, line 27, in ble_client_on_connected_event
File ‘m5ble/m5ble.py’, line 556, in set_mtu
ValueError: Not connected to a server

I set the MTU within the ‘ble_client_on_connected_event’ function, which is only called after connecting to the server, and I can both read and write with the server.

]]>https://community.m5stack.com/post/30201https://community.m5stack.com/post/30201Tue, 18 Nov 2025 10:07:27 GMT