I need help increasing ATT MTU.

RE: I need help increasing ATT MTU.

julian24 — Mon, 03 Feb 2025 17:43:30 GMT

Okay, so this was much simpler than i thought. Thanks for clarifying, I'll consider connect SDK

RE: I need help increasing ATT MTU.

Hieu — Fri, 31 Jan 2025 15:56:19 GMT

Hi julian24,

23 probably was the max possible value in the very first release of Bluetooth LE. With the SDK you are using, 103 is perfectly possible.

Once again, please use the nRF Connect SDK if possible.

RE: I need help increasing ATT MTU.

julian24 — Fri, 31 Jan 2025 12:57:58 GMT

Hi Hieu,

in the NUS example, NRF_SDH_BLE_GATT_MAX_MTU_SIZE is set to 23, which means the max length supported over NUS is 20, and it's just not enough for my program.

Can I just set NRF_SDH_BLE_GATT_MAX_MTU_SIZE to, say, 103, so i can work with a max length of 100? Are there no consequences or anything to consider regarding this? I remember that on nRF51822 23 was the max possible value.

Thanks for your help

RE: I need help increasing ATT MTU.

Hieu — Thu, 30 Jan 2025 13:58:43 GMT

Hi julian24,

You will need to change NRF_SDH_BLE_GATT_MAX_MTU_SIZE in sdk_config.h. That being said, I believe it is already setup to a big value in the NUS example.

If you are just beginning to explore using nRF device for BLE, I recommend using the nRF Connect SDK though. The nRF5 SDK is in maintenance mode and will not receive any feature updates.

Hieu