S113 SoftDevice MTU limit on nRF52833

[strongman]

Question:

What's the maximum NRF_SDH_BLE_GATT_MAX_MTU_SIZEsupported by S113 v7.2.0 on nRF52833?

Current setup:

• Chip: nRF52833

• SoftDevice: S113 v7.2.0

• Max working MTU: 247 bytes

Can we set MTU larger than 247? If not, what's the technical limitation?

Thanks for your help.

[Sigurd]

Hi!

You should be able to set it to 512, but you might need to allocate more RAM to the SoftDevice for it to work. See e.g. this page:  Adjustment of RAM and Flash memory

From the Bluetooth spec:

From BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 3, Part F page 1485:

"The maximum length of an attribute value shall be 512 octets."

 PS: If this is a new project, I strongly recommend using nRF Connect SDK instead: https://www.nordicsemi.com/Products/Development-software/nrf-connect-sdk