Semtech LR1121 - Table 8-24: Maximum User Payload Length, in Bytes

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
81 of 130
Semtech
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• Grid: frequency hopping grid step size:
 0x00: 25.390625kHz for FCC use case
 0x01: 3.90625kHz for non-FCC use case
• Hopping: configures intra-packet hopping:
 0x00: no hopping (test purpose)
 0x01: hopping
• BW: bandwidth occupied by the frequency hopping pattern:
 0x00: 39.06kHz
 0x01: 85.94kHz
 0x02: 136.72kHz
 0x03: 183.59kHz
 0x04: 335.94kHz
 0x05: 386.72kHz
 0x06: 722.66kHz
 0x07: 773.44kHz
 0x08: 1523.4kHz
 0x09: 1574.2kHz
 Other values are RFU
• Hop sequence: 9-bit integer, seed of the pseudo-random frequency hopping sequence:
 value in [0; 383] for Grid=0x00, BW in {0x06, 0x07, 0x08, 0x09}
 value in [0; 383] for Grid=0x01, BW in {0x00, 0x01, 0x02, 0x03}
 value in [0; 511] for Grid=0x01, BW in {0x04, 0x05, 0x06, 0x07, 0x08, 0x09}
• DeviceOffset: per device frequency offset to reduce the risk of packet collision. Frequency offset (Hz) = DeviceOffset *
488.28125Hz:
 signed value in [-26; 25] for Grid = 25.390625kHz
 signed values in [-4; 3] for Grid= 3.90625kHz
For a FCC use case, DeviceOffset shall not be changed once configured.
• Payload: actual payload to encode. Returns CMD_OK if the parameters are valid and if the payload can be encoded,
CMD_PERR otherwise.
The maximum supported packet length is 255 coded bytes. The maximum user payload length is given by the Table 8-24:
Maximum user payload length, in bytes.
A FCC use case corresponds to a use case where BW = 0x08/0x09, Hopping = 0x01, Grid = 0x00.
Note: This command does not send the LR-FHSS packet. The transmission will be triggered using SetTx(...) command.
Table 8-24: Maximum user payload length, in bytes
CR HeaderCount=1 HeaderCount=2 HeaderCount=3 HeaderCount=4
CR=5/6 189 178 167 155
CR=2/3 151 142 133 123
CR=1/2 112 105 99 92
CR=1/3 74 69 65 60