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 50 of 66
8.1.3.
Firmware Update Protocol on the Host System
This chapter describes the protocol layer used for firmware update over serial on the
S42/Central.
The table below contains the maximum possible binary firmware sizes:
Firmware variant
Maximum possible binary firmware size
V3.002
332 kBytes
Note: The actual size of each firmware binary file can be found in the firmware release
notes.
8.1.3.1.
Layer Structure
The device firmware update uses the HCI Three-Wire UART Transport Layer specified in
Bluetooth 4.0 Core Specification
. Instead of HCI frames, four different DFU packets are sent
to the S42/Central over the UART serial interface using this transport.
8.1.3.2.
DFU Packet Layer
There are four different packet types in this layer. The packet type is an unsigned 32 bit integer
in LSB first order.
1. Start packet
0x00000003
2. Init packet
0x00000001
3. Application data packet
0x00000004
4. Stop packet
0x00000005
DFU packet layer
Three wire UART
packet layer
SLIP layer
UART