LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
67 of 130
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8.3 LoRa® Commands
8.3.1 SetModulationParams
Command SetModulationParams(...) configures the modulation parameters for the selected modem. Since the
parameters are modem dependent, the description hereafter is valid only for the LoRa modem.
• SF defines the spreading factor (values other than those below are RFU). SF5 and SF6 are compatible with the SX126x
device family. SF6 can be made compatible with the SX127x family in implicit mode via a register setting
1
.
0x05: SF5
0x06: SF6
0x07:SF7
0x08: SF8
0x09: SF9
0x0A: SF10
0x0B: SF11
0x0C: SF12
• BWL defines the LoRa modulation bandwidth (values other than those below are RFU):
0x03: LoRa_BW_62, LoRa Bandwidth 62.5kHz
0x04: LoRa_BW_125, LoRa Bandwidth 125kHz
0x05: LoRa_BW_250, LoRa Bandwidth 250kHz
0x06: LoRa_BW_500, LoRa Bandwidth 500kHz
0x0D: BW203 (2.4GHz band only)
0x0E: BW406 (2.4GHz band only)
0x0F: BW812 (2.4GHz band only)
• CR configures the Coding Rate (values other than those below are RFU):
0x01: Short Interleaver CR= 4/5 Overhead Ratio 1.25
0x02: Short Interleaver CR= 4/6 Overhead Ratio 1.5
0x03: Short Interleaver CR= 4/7 Overhead Ratio 1.75
0x04: Short Interleaver CR= 4/8 Overhead Ratio 2
0x05: Long Interleaver CR= 4/5
2
Overhead Ratio 1.25
0x06: Long Interleaver CR= 4/6
2
Overhead Ratio 1.5
0x07: Long Interleaver CR= 4/8
2
Overhead Ratio 2
• LowDataRateOptimize reduces the number of bits per symbol:
0x00: LowDataRateOptimize off
0x01: LowDataRateOptimize on
Table 8-4: SetModulationParams Command
Byte 0 1 2 3 4 5
Data from Host 0x02 0x0F SF BWL CR LowDataRateOptimize
Data to Host Stat1 Stat2 IrqStatus(31:24) IrqStatus(23:16) IrqStatus(15:8) IrqStatus (7:0)
1.Set bit 18 of register at address 0xf20414 to 1
2.Long Interleaver (CR=4/5, 4/6 and 4/8) is supported for packets of minimum Payload length of 8 bytes, and maximum Payload length of 253
bytes if the CRC is activated (255 bytes if the CRC is deactivated).
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