Changing BLE packet size

[SentinelLighting]

Project: Variation of Nordic ble_peripheral project

SDK: 15.1,  Softdevice : 132 rev 6.1

How do you change the BLE packet length?  I have a project where I defined a characteristic to be 132 bytes.  It is set to notify (notification).  Another developer has created the ble APP, when the App connects to my code and then goes to 'stream' the characteristic.  The first time it gets data from my firmware it gets a full 132 byte packet.  Then somehow the packet length changes to 20.  I ALWAYS write 132 bytes to be transmitter (using sd_ble_gatts_hvx).    Any clues on why this is happening?   Who might be changing the packet size?  The softdevice or the app?

[SentinelLighting]

Can anyone get me more details?  When I define a characteristic as 132 bytes and set it to notification, how do I get it to transmit all 132 bytes?  Currently it seems only 20 bytes are being transmitted (after the first transmission).  If there is a negotiation on connection to set the length how do I stop it from changing it smaller?   Also is the MTU always set to 27 and not changeable?  If you want more data do you need to send multiple packets?  HELP!

[Einarh]

In order to transmit larger payloads than default, you have to set the Maximum ATT_MTU and Data Length variables in your application. You also have to make sure that an ATT_MTU exchange takes place and that larger payloads are supported by both your central and peripheral device.

Please see the Throughput Example for a complete usage example.

-Einar