Queued Writes characteristic value longer than 220B

RE: Queued Writes characteristic value longer than 220B

Pål Håland — Fri, 21 Nov 2014 11:13:42 GMT

If you have a 250 byte long characteristic value it would be: ceil(250*23/17)+2 = 341 byte

Not sure if it is documented anywhere, the structure used for reading back the part values can be located here: developer.nordicsemi.com/.../a01075.html

RE: Queued Writes characteristic value longer than 220B

Piko — Fri, 21 Nov 2014 10:38:40 GMT

Hello Thanks for answer. But my problem isn't space provided by me. When I receive BLE_EVT_USER_MEM_REQUEST I allocate by sd_ble_user_mem_reply memory block equals to characteristic value = 250B. I even try allocate more = 300. But, with that you write, this means that I need more memory than characteristic value lenght. Is this right? Where I can read about that? thanks Piko

RE: Queued Writes characteristic value longer than 220B

Pål Håland — Fri, 21 Nov 2014 10:25:45 GMT

Piko, the best way to determine how much space you should provide when you receive BLE_EVT_USER_MEM_REQUEST is the following calculation.

H = handle (2 byte) + offset (2 byte) + length (2 byte) = 6
MTU = 23
DATA = MTU-H = 17

Total Memory = ceil(Char Max Len*MTU/DATA) + 2