LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
75 of 130
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8.5.2 SetPacketParams
Command SetPacketParams(...) configures the parameters of the RF packet for the selected modem. Since the
parameters are modem dependent, the description hereafter is valid only for the (G)FSK modem.
• PblLengthTX defines the (G)FSK packet preamble length in bits. Coded on 2 bytes, from 0x0008 (8 bits) to 0xFFFF
(65535 bits).
• PblDetect defines the preamble detector length. The preamble detector acts as a gate to the packet controller, when
not 0x00 (preamble detector length off), the packet controller only becomes active if a certain number of preamble
bits have been successfully detected by the radio.
0x00: Preamble detector length off
0x04: Preamble detector length 8 bits
0x05: Preamble detector length 16 bits
0x06: Preamble detector length 24 bits
0x07: Preamble detector length 32 bits
• SyncWordLen defines the length of the Syncword in bits. The Syncword is programmed by SetGfskSyncWord(...).
• AddrComp allows conditioning the packet reception to a predefined peer device address. Node address and broadcast
address can be set with the SetPacketAdrs(...) command. If the address comparison fails then the packet
reception is aborted and the adrsErr flag is set.
0x00: Address Filtering Disabled
0x01: Rx & Tx: Address Filtering activated on Node address
0x02: Address Filtering activated for Rx on Node & broadcast addresses, for Tx on Node address
• PacketType defines the length of the incoming packet.
0x00: Packet length is known on both sides, the size of the payload is not added to the packet
0x01: The packet is of variable size, PayloadLen is the size of the packet (with header encoded on 8 bits)
0x02: The packet is of variable size, PayloadLen is the size of the packet - compatible with SX128x chip (with header
encoded on 9 bits)
• PayloadLen defines the size of the payload (bytes) to transmit or the maximum payload size the receiver can accept.
In explicit header mode:
0: Reception of any payload length between 0 and 255 bytes allowed
N: Reception of any payload length between 1 and N bytes accepted. Payload lengths of 0 or > N are rejected
and result in a HeaderErr IRQ
In implicit header mode, PayloadLen configures the exact length of the payload to be transmitted or received.
• CrcType defines the packet CRC. The CRC can be fully configured and the polynomial used, as well as the initial values
can be entered directly through command SetGfskCrcParams(...):
0x01: CRC_OFF (No CRC)
0x00: CRC_1_BYTE (CRC computed on 1 byte)
0x02: CRC_2_BYTE (CRC computed on 2 bytes)
0x04: CRC_1_BYTE_INV (CRC computed on 1 byte and inverted)
0x06: CRC_2_BYTE_INV (CRC computed on 2 bytes and inverted)
• DcFree enables whitening on the RF packet.
0x00: No encoding
0x01: SX127x/SX126x/LR1110 compatible whitening enable
0x03: SX128x compatible whitening enable
Table 8-15: SetPacketParams Command
Byte 0 1 2 3 4 5 6 7 8 9 10
Data from Host 0x02 0x10
PblLength
TX(15:8)
PblLength
TX(7:0)
Pbl
Detect
Sync
WordLen
Addr
Comp
Packet
Type
Payload
Len
Crc
Type
DcFree
Data to Host Stat1 Stat2
IrqStatus
(31:24)
IrqStatus
(23:16)
IrqStatus
(15:8)
IrqStatus
(7:0)
0x00 0x00 0x00 0x00 0x00
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