LMX9820SBX/NOPB National Semiconductor, LMX9820SBX/NOPB Datasheet - Page 24

• Manufacturer Part Number: LMX9820SBX/NOPB
• Manufacturer: National Semiconductor

Specifications of LMX9820SBX/NOPB

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12.0 Command Interface
The LMX9820 offers Bluetooth functionality in either a self
contained slave functionality or over a simple command
interface. The interface is listening on the UART interface.
The following sections describe the protocol transported on
the UART interface between the LMX9820 and the host in
command mode (see Figure 17). In Transparent mode, no
data framing is necessary and the device does not listen
for commands.
12.1 FRAMING
The connection is considered “Error free”. But for packet
recognition and synchronization, some framing is used.
All packets sent in both directions are constructed per the
model shown in Table 27.
12.1.1 Start and End Delimiter
The “STX” char is used as start delimiter: STX = 0x02. ETX
= 0x03 is used as end delimiter.
.
ID
0x52
‘R’
0x43
‘C’
0x69
‘i’
0x72
‘r’
Start De-
limiter
1 Byte
Direction
REQUEST
(REQ)
Confirm
(CFM)
Indication
(IND)
Response
(RES)
- - - - - - - - - - - - - Checksum - - - - - - - - - - - - -
Type ID
Packet
1 Byte
Opcode
1 Byte
Description
A request sent to the Bluetooth module.
All requests are answered by exactly one confirm.
The Bluetooth modules confirm to a request.
All requests are answered by exactly one confirm.
Information sent from the Bluetooth module that is not a direct confirm to a request.
Indicating status changes, incoming links, or unrequested events.
An optional response to an indication.
This is used to respond to some type of indication message.
LMX9820
Table 28. Packet Type Identification
Figure 17. Bluetooth Functionality
Data Length
UART
Table 27. Package Framing
2 Bytes
24
12.1.2 Packet Type ID
This byte identifies the type of packet. See Table 28 for
details.
12.1.3 Opcode
The opcode identifies the command to execute. The
opcode values can be found within the “LMX9820 Software
User’s Guide” included within the LXMX9820 Evaluation
Board.
12.1.4 Data Length
Number of bytes in the Packet Data field. The maximum
size is defined with 333 data bytes per packet.
12.1.5 Checksum:
This is a simple Block Check Character (BCC) checksum
of the bytes “Packet type”, “Opcode” and “Data Length”.
The BCC checksum is calculated as low byte of the sum of
all bytes (e.g., if the sum of all bytes is 0x3724, the check-
sum is 0x24).
Checksum
1 Byte
UART
without Bluetooth™
<Data Length> Bytes
Existing device
capabilities
Packet Data
End De-
limiter
1 Byte