what is the maximum number of characteristics allowed in one service?

[nikunj8086]

hi,

i am using Nordic thingy:52 with a nRF52840 with s140 softdevice to receive multiple characteristic data from thingy like thingy environment service have 6 characteristics, as of now i am able to receive all 6 characteristics data from environment service, but with other service like thingy motion service which have 10 characteristics, but still my nRF52840 detecting only 6 characteristics i have verified with other which has less characteristics then 6, it detects all characteristics but with services with more then 6 characteristics i am getting maximum 6 characteristic number.

i have referred weather station program from "http://evalspace.com/". here i have verified from debugging and checking value of "p_evt->params.discovered_db.char_count" which is 6 even from thingy motion service.

please help me to fix this and receive at least 10 characteristics data.

[Petter Myhre]

Which SDK and SoftDevice version are you using? How are you doing this discovery? What functions and arguments are you calling on the central side? Do you have a sniffer trace? Could you elaborate a bit?

[nikunj8086]

in sdk 14.2 maximum characteristics are limited to 6 by a macro "BLE_GATT_DB_MAX_CHARS" within the header file "ble_gatt_db.h". change macro definition to required number of characteristics. it will work.

[KV]

Is there any limitation on increasing the max number of characteristics to a higher value (say 30)? Will this impact the time taken for service discovery? I am sure that memory consumption may be more.

Is there any recommendation for a max number?

[Petter Myhre]

Don't think so, it is as you say a question about how much memory that is reserved.

There is no recommendation, it depends on the the number of characteristics in the services you are going to discover.

[silivanov]

Help!

I can't add more then three characteristics. The programm go to app_error_fault_handler with :

id - 16385, pc - 269269, info - 536957184

I assume there is not enough memory. 

Which memory should be allocated more?

I use SDK15, s140v6.0.0

RAM start: 0x20002AB8

CSTACK: 8192

HEAP: 8192

Also I use FREERTOS