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 51 of 66
Start packet
With the “Start packet” the DFU bootloader is informed about the kind of update and the length
of the binary image. The length of the image is an unsigned 32 bit integer in LSB first order. It
is length of the file with the “.bin” extension in the Telit delivery package (zip file). For a binary
application with image size of 17,336 bytes (0x000043B8), the packet is coded as:
Byte1
Byte2
Byte3
Byte4
Byte5
Byte6
Byte7
Byte8
0x03
0x00
0x00
0x00
0x04
0x00
0x00
0x00
1.
Byte9
Byte10
Byte11
Byte12
Byte13
Byte14
Byte15
Byte16
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
2.
Byte17
Byte18
Byte19
Byte20
0xB8
0x43
0x00
0x00
Init packet
The init packet contains information about the application that is transferred. The DFU
bootloader checks this information to determine if the image is valid for the device. Please use
as contents only the init packet provided by Telit. The data starting with “Device type” and
ending with “CRC of the image that will be transferred” (see the Nordic documentation) is
provided by Telit in the Telit delivery package (zip file). It is the contents of the file with the
extension “.dat”. The binary application to load with the data packets is the file with the “.bin”
extension.
The init packet is coded as:
Byte1
Byte2
Byte3
Byte4
Byte5 up to Byte n
Byte n+1
Byte n+2
0x01
0x00
0x00
0x00
Contents of the “.dat”
file. The length is
variable.
0x00
0x00
Required waiting
After accepting the init packet the bootloader prepares (erases) the internal flash memory to
accommodate the new image. The bootloader accepts no data packets during this time. Please
wait 10 seconds before sending the first data packet.
Application data packet
With the Application data packet the binary application image is transferred to the
S42/Central. The binary application to load with the data packets is the file with the
“.bin” extension in the Telit delivery package (zip file). The maximum packet size is 512 bytes
of data + header per packet. Each packet is coded:
Byte1
Byte2
Byte3
Byte4
Byte 5 … up to Byte 516
0x04
0x00
0x00
0x00
Max 512 bytes of binary application data