Data Sheet

Byte
Value
Data Type
Description
0
0x06
8 bit unsigned integer
Number of bytes in the packet (6).
1
0x01
8 bit unsigned integer
Code for Data Packet
2:5
TxID
32 bit unsigned integer
Encoded 32 bit integer representing the
Dexcom G4 Transmitter ID that the bridge is
filtering packets on.
Note: as this packet is sent from the app to the phone, it does not include a XBridge protocol
level byte.
The TXID packet is part of Protocol Functional Level 1, although the app does not send this
byte tag to the bridge device.
Beacon packet
The Beacon packet is sent from the bridge to the phone app to indicate which Dexcom G4
Transmitter ID it is filtering on. The app can use this beacon to know when the bridge is
active, and if it has a different Transmitter ID to what the app is configured for, it can correct
this by sending a TXID packet.
The structure of the Beacon packet is as follows:
Byte
Value
Data Type
Description
0
0x06
8 bit unsigned integer
Number of bytes in the packet (6).
1
0xF1
8 bit unsigned integer
Code for Data Packet
2:5
TxID
32 bit unsigned
integer
Encoded 32 bit integer representing the
Dexcom G4 Transmitter ID that the bridge
should filter packets on.
6
XBridge Protocol
Level
8 bit unsigned integer
XBridge protocol level. Indicates the
protocol level of xBridge. Note, that
currently this will be 0x01.
Note, this packet also doubles as the acknowledgement packet for a TXID packet. When
the app receives this packet it can be sure that this is the Transmitter ID value set in the
wixel flash memory.
The Beacon packet is part of Protocol Functional Level 1.
Decoding and Encoding a Transmitter ID Long Int
In order for the app to send the correct value in a TXID packet to the bridge, you need to be
able to encode the text of the Transmitter ID to a long int. This is done using the following
pseudo code, taken directly from the original xBridge code. Your app will need to replicate
this process in order to send the correct data.
char SrcNameTable[32] = { '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P',
'Q', 'R', 'S', 'T', 'U', 'W', 'X', 'Y' };
/* asciiToDexcomSrc - function to convert a 5 character string into
a unit32 that equals a Dexcom transmitter Source address. The 5