Semtech LR1121 - LR-FHSS Commands; Setmodulationparams; Lrfhssbuildframe; Table 8-22: Setmodulationparams Command

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
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8.7 LR-FHSS Commands
8.7.1 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 LR-FHSS modulation.
• BitRate defines the LR-FHSS Bit rate in bits per second. Bitrate in bits/s is Bitrate(30:0)/256, with Bitrate(31) =1. For
example, 488.28215Hz bit rate will be coded Bitrate=125000 with Bitrate(31) =1.
In the current LR-FHSS implementation, only 488.28215 Hz is supported, other values are RFU.
• PulseShape defines the filtering applied to the LR-FHSS packet:
 0x0B: Gaussian BT 1. Other values are RFU
8.7.2 LrFhssBuildFrame
Command LrFhssBuildFrame(...) encodes the given payload and configures the internal hopping table
• HeaderCount: number of Headers for the LR-FHSS packet: 1, 2, 3 or 4
• CR: configures the Coding Rate:
 0x00: CR= 5/6
 0x01: CR= 2/3
 0x02: CR=1/2
 0x03: CR= 1/3
• ModType: 0=GMSK modulation, 488.28125bps data rate
Table 8-22: SetModulationParams Command
Byte 0 1 2 3 4 5 6
Data from
Host
0x02 0x0F
BitRate
(31:24)
BitRate
(23:16)
BitRate
(15:8)
BitRate
(7:0)
PulseShape
Data to Host Stat1 Stat2
IrqStatus
(31:24)
IrqStatus
(23:16)
IrqStatus
(15:8)
IrqStatus
(7:0)
0
Table 8-23: LrFhssBuildFrame Command
Byte 0 1 2 3 4 5 6 7
Data from Host 0x02 0x2C HeaderCount CR ModType Grid Hopping BW
Data to Host Stat1 Stat2
IrqStatus
(31:24)
IrqStatus
(23:16)
IrqStatus
(15:8)
IrqStatus
(7:0)
0 0
Byte 8 9 10 11 12 ... ...
Data from Host
HopSequence
(8)
HopSequence
(7:0)
DeviceOffset Payload[0] Payload[1] ... Payload[N]
Data to Host 0 0 0 0 0 ... 0