Configurable MTU: Do we still need long writes ?

RE: Configurable MTU: Do we still need long writes ?

Petter Myhre — Wed, 10 Jan 2018 15:34:21 GMT

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.

RE: Configurable MTU: Do we still need long writes ?

yacine — Wed, 10 Jan 2018 15:17:35 GMT

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 ?

RE: Configurable MTU: Do we still need long writes ?

Petter Myhre — Wed, 10 Jan 2018 11:24:58 GMT

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?

RE: Configurable MTU: Do we still need long writes ?

yacine — Wed, 10 Jan 2018 10:33:09 GMT

for sending more than 20 bytes to the peripheral. isn't it what means "long" ?

RE: Configurable MTU: Do we still need long writes ?

Petter Myhre — Wed, 10 Jan 2018 09:57:19 GMT

What were you using the long write for?

RE: Configurable MTU: Do we still need long writes ?

shibshab — Wed, 10 Jan 2018 07:22:47 GMT

If the value to be written is <= (ATT_MTU - 3) then you do not need a long write, but can perform a regular ATT Write Request/Command.