Configurable MTU: Do we still need long writes ?

[yacine]

Hello

I noticed that since S132 v3.x.x we can configure the MTU. Does all the posts referring to long writes in this forum apply to the situation before this feature ?

thanks

[Petter Myhre]

Ok. I just wanted to check. You don't need long writes to send more than 20 bytes to the peripheral, but it is one way of doing it. You need long writes to write to the part of characteristic values that are longer than the ATT MTU, and if you want to do a write with an offset.

Could you elaborate a bit on what your question is? Which post are you referring to? Which situation?

[yacine]

I dont know this:

write with an offset

but concerning this:

the part of characteristic values that are longer than the ATT MTU

->I dont understand when this case can happen if you are able to augment the MTU. is there a MTU max ? if yes why isn't it the norm instead of 23 bytes ?

[Petter Myhre]

It can happen if you don't change the ATT MTU, or if you change it to an ATT MTU that is shorter than the characteristic value. Not all peers support configuring the ATT MTU, and not all peers allows changing it to anything. Having a larger ATT MTU requires more memory, for one thing.