Maximum number of characteristics

[Mahendra Tailor]

Hi I am using S110 v6.0.0 I have written an app that has a single service and I then register the same characteristics until it fails. The properties is 0xA (read/write). When I use _VLOC_STACK it runs out of memory and for value len=10 I can register 24 characteristics and for value len = 20 I can register 20 (for value len = 1, I can register 29)

I then modified my app so that it uses _VLOC_USER and then regardless of value len I can register 30 for all.

We have a customer who is asking to be able to register at least 33 characteristics spread over 8 services. My guess is that registering the service attribute is going to reduce that number down even more.

Is there anything you can suggest?

Look forward to hearing from you

[Ulrich Myhre]

You should be able to use a combination of both.

The stack memory allotted is already reserved for GATT, so you can use that until you run out. The rest of the characteristics can then be added with VLOC_USER.

It seems strange to have that many services and characteristics added though. Are you positive that you need to implement 33 characteristics for your needs?

[Mahendra Tailor]

Hi Thank you for getting back. You say "The rest of the characteristics can then be added with VLOC_USER." Not true because even for VLOC_USER (for everything) it needs to use the 'stack' memory for the uuid and the handles. That is why when I use VLOC_USER for everything I still run out of memory.

A customer has asked for the 33 characteristics. They are king :-) we have to make it happen if in our powers. We pride ourselves in customer service.

Another curious behaviour, which is very annoying as I cannot fathom the reason yet ...

I have a test application where I register a character with property = 0x2A (read/write/indicatable) with VLOC_STACK and it works.

I changed the application so that it has VLOC_USER ( I stress no other change) and now the function sd_ble_gatts_characteristic_add() is returning with an nrf error of 7 (INVALID PARAMETER)

Why does just changing the location memory make the parameters fail?

I can't find any documentation to tell me WHICH parameter is inva

[Mahendra Tailor]

Another observation I have test code that uses VLOC_STACK and I register chracteristics with various different properties. They all successfully register.

I then change the firmware so that where I use VLOC_STACK I specify VLOC_USER. In this case only the properties with 0xA value succeeds. All the others come back with INVALID_PARAM error code.

Question, why should just changing the location of the memory make that happen?

[Mahendra Tailor]

I am using v6.0.0. Does anyone know if the behaviour on newer stack is different?

[Ulrich Myhre]

See ble_gatts_attr_t here devzone.nordicsemi.com/.../a00270.html You should have to set the p_value to a buffer when using VLOC_USER.