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 52 of 66
Stop packet
When the Application image has been transferred to the S42/Central boot loader the
image must be activated. The stop packet will inform the boot loader that transferring of the
image has completed and the application can be started. The packet is coded as:
Byte1
Byte2
Byte3
Byte4
0x05
0x00
0x00
0x00
8.1.3.3.
Three Wire UART Packet Layer
Every packet that is sent over the Three-Wire UART Transport Layer has a packet header. It
also has 16 bit CCITT-CRC at the end of the payload.
Each transport packet will contain one higher layer packet. A transport packet consists of a
Packet Header of 4 octets, a payload of 4 to 516 octets, and a 16 bit CCITT-CRC.
The Packet header consists of a Sequence Number of 3 bits, an Acknowledge Number of 3 bits,
a Data Integrity Check Present bit, a Reliable Packet bit, a Packet Type of 4 bits, a Payload
Length of 12 bits and a 8 bit Header Checksum.
The used Packet Type is vendor specific (0xe).
LSB
MSB
4 Octets
1.. 156 Octets
2 Octets
Packet Header
DFU packet layer
16 bit CCITT-CRC
The detailed format description of the used packet header can be found in
Bluetooth 4.0 Core
Specification
.
For a detailed description of the procedural requirements of this protocol have a look in the
Bluetooth 4.0 Core Specification
, chapter “Three-Wire UART Transport Layer”.
8.1.3.4.
SLIP Layer
The SLIP layer performs octet stuffing on the octets entering the layer so that specific octet
codes which may occur in the original data do not occur in the resultant stream.
The SLIP layer places octet 0xC0 at the start and end of every packet it transmits.
Any occurrence of 0xC0 in the original packet is changed to the sequence 0xDB 0xDC before
being transmitted. Any occurrence of 0xDB in the original packet is changed to the sequence
0xDB 0xDD before being transmitted. These sequences, 0xDB 0xDC and 0xDB 0xDD are
SLIP escape sequences
.
For a detailed description of this protocol have a look in the
Bluetooth 4.0 Core Specification
,
chapter “Three-Wire UART Transport Layer”.
