S42/Central Software User Guide
1VV0301318 Rev. 3
– 2018-08-31
Reproduction forbidden without written authorization from Telit Communications S.p.A.- All Rights Reserved.
Page 23 of 66
3.2.
MUX Mode
To handle connections to peripheral devices and the Terminal I/O connection in parallel the
S42/Central supports the multiplexing (MUX) mode.
In this mode there is an always accessible AT command channel available.
This command channel (channel ID= “FF”) enables the possibility to handle all four links in
parallel (three GATT connections to peripheral devices and one Terminal I/O connection).
The host has to implement the simple to use multiplexing protocol.
Data has to be sent and are received in the following framing (all values in hexadecimal format):
Name
Description
Length
Value
Start
Start of frame
8 bit
CC
Data
Channel ID
Channel identifier
8 bit
00 – FE
Command
Channel ID
Channel identifier
8 bit
FF
Length
Length of data
8 bit
-
Data
Max. 255 bytes data
Min. 0 byte
Max. 255 bytes
-
Start of frame, channel ID, length and data are always transmitted in direct, binary form.
A detailed description of the multiplexing mode is listed in the
S42/Central AT
Command Reference
.
3.2.1.
Central Role as GATT Client
In the multiplexing mode the S42/Central supports the possibility to connect to any
Bluetooth low energy peripheral device and the Terminal I/O connection in parallel.
The following example lists one GATT connection and one Terminal I/O connection in multiple
steps.
