RE: BLE MTU size

Turbo J — Wed, 18 Feb 2026 08:33:38 GMT

Check .config (build/zephyr subdir) for CONFIG_MCUMGR_TRANSPORT_NETBUF_SIZE. Must be bigger than BTLE MTU, try 1024 bytes.

My samples here run CONFIG_MCUMGR_TRANSPORT_NETBUF_SIZE=2475

But that is rather big for shell command buffers (dummy backend is configured to use 2KB buffer).

BTLE speed can be increased with lower connection interval parameters, but with a 512 MTU only up to a point. I've managed to push 100KByte/sec reading from an SD card (SPIM) while transferring the data out via BTLE notifications in parallel. SoC is NRF5340.

But that code does not use mcumgr transport, that one should be a bit slower.