Efficient way of using characteristics

[Andreas]

Hello,

I am working on optimizing my BLE transfer algorithm. Therefore I am searching for an efficient way of using the characteristics. Example: At the moment I have 2 characteristics called “longitude” and “latitude” in a service. Size of both is 2 byte (int16_t). Is it more efficient to merge them together into one characteristic called “coordinates” with a length of 4 byte? What about the difference in stack usage of the softdevice (S120) in this two cases?

Thanks in advance

BR BTprogrammer

[Hung Bui]

Hi,

It's better to group the 2 characteristic into one, you will save a lot of overhead. Also there is another limitation on the number of packet per connection interval. Some central only allow 1 packet per connection interval, by grouping the 2 characteristics you can send more data. The maximum payload size of a packet is 20 bytes.

[Andreas]

Hello Hung, thanks for your reply. That was also my feeling. Thanks for your confirmation. Does this change the RAM/Stack usage of the softdevice?

[Hung Bui]

Yes, it will save you some little space for the RAM of the Attribute table. But not the RAM used for number of connection as when configuring the softdevice (the RAM area for application)

[Andreas]

Thank you very much.

[junsoo337]

dear Hung, i would like to ask you for more detail technical information about "a lot of overhead" and "by grouping the 2 characteristics you can send more data"

2-characteristic than 1-characteristic have a overhead more? isn't it? why the group can send more data when 1 packet?

thank you