RE: What is the maximum MTU size supported on nRF52840

brianreinhold — Thu, 24 Jun 2021 13:45:38 GMT

Sigurd,

I sort of figured this out by trial and error. However, I will say trying t find the error codes is very difficult because of the way they are defined. There needs to be a place where they are all listed by value.

RE: What is the maximum MTU size supported on nRF52840

Sigurd — Thu, 24 Jun 2021 12:34:15 GMT

There is no limit per the spec on how high the ATT MTU value can be, but the maximum length of an attribute value is per spec 512 octets. The Softdevice supports this value.

When you configure the SoftDevice. i.e. you configure how many connections it should support, connections roles, GAP event length, maximum ATT MTU, number of custom UUIDS, size of GATTS attribute table, etc. this is passed to the SoftDevice when you enable it, and it will return the RAM requirements for the configuration. If you have not configured enough RAM, you will not be able to enable the SoftDevice (sd_ble_enable() will return NRF_ERROR_NO_MEM.)

[quote user="brianreinhold"]It looks like a new MTU requires a new memory size which has to be hard-configured pre-build. There does not appear to be a way to do this dynamically.[/quote]

Correct.

[quote user=""]<debug> app: Could not set the Bluetooth Address. Error code 12289[/quote]

12289 in hex is 0x3001. ie. NRF_ERROR_STK_BASE_NUM (0x3000) +1 , this is the same as BLE_ERROR_NOT_ENABLED

What I believe happened here is that the sd_ble_enable() returned NRF_ERROR_NO_MEM, i.e. the SoftDevice was not enabled, then you later called sd_ble_gap_addr_set(), and it returned BLE_ERROR_NOT_ENABLED because sd_ble_enable() had failed/the SoftDevice was not enabled.

RE: What is the maximum MTU size supported on nRF52840

brianreinhold — Tue, 22 Jun 2021 13:05:11 GMT

It looks like a new MTU requires a new memory size which has to be hard-configured pre-build. There does not appear to be a way to do this dynamically.