Hi,

I have for some time now looked into the GATT protocol to use this in a Bluetooth Low Energy application.

I have come to the point where I am able to set up a service with multiple characteristics.

My question now is:
I want to be able to read/write an IP address over BLE, also I would like to be able to read a table of values over the BLE.
How do I set this up? this far I have only set up characteristics with one value, but need to be able to read the struct as shown below:

struct mytable {
uint32_t IPaddress;
uint8_t xdata[100];
}

I am thinking like this:
Service
____Characteristic for IP address
_______Declaration
_______value
_______User description
____characteristic for xdata
_______Declaration
_______Value
_______ User Description

Do I have to split the IPaddress in two 16 bit values to keep under 20-bit limit? Or can I send 32bit at once?

How can I read the whole table (or parts of it based on a counter). How do I refer the parts of the table I want to read to the GATT protocol, pointer and counter? How would this look like when I am setting up the value part of the characteristic?

Many thanks in advance.

 

I saw now that it is 20 byte that is the limit,so the 32bit value should work just fine.

But how will it work with the larger table?

 

Segment the large table into smaller tables ( 20 byte limit) with individual characteristics, offset or indexes. You need to implement a segmentation and reassembly mechanism in application space if you can't request greater MTU values.

https://community.nxp.com/thread/332030

 

Hi,

ok, thank you