Write to variable length characteristic

[Naveen]

I want to send 512 bytes of data over ble through the characteristic value, as maximum length of the characterstic value is 512. When I try to do the transfer more than 20 bytes, it will fail. When I checked in this forum, I got know that we can only transfer 20 bytes each time and make a simulation of 512 byte transfer by continuous calling "write" function with offset increment. Even I checked the all sample code get this code of simulating this. I did not find any sample. If any one implemented the code which can transfer 512 byte, kindly share this.

[FormerMember]

If you want to transfer more than 20 bytes from the GATT Client to GATT Server, GATT Long write has to be used, see this post.

If you want to transfer more than 20 bytes from GATT Server to GATT Client, read blob or notification can be used.

[Naveen]

I will come back on this example. As it is not working properly with Master Control Panel, I will check with iphone.

[Ulrich Myhre]

Long writes can be used to write everything in a single go, even across multiple characteristics, but it is not required to write to longer attributes. If it is acceptable that the data is half-written at any point, writing with an offset is perfectly possible.