XTR-8LR-USB
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User Manual
The technical features can change without forecasting. AUR°EL S.p.A doesn’t assume any responsa ility of demage due to the improper use of the device.
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Tel.: +39.0546.941124 Fax: +39.0546.941660
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Above Charts show increased sensitivities for increased SF values; decreased data rate for increased SF and
decreased Bandwidths.
The parameters choice have to be made by assessing at first, the bandwidth: if more channels are requested
it's mandatory to choose 20,8 KHz BW, otherwise, 62,5 or 125 KHz BW.
In this case SF value equals to 8-10 is the best trade-off between RF sensitivity and flying time.
Very often in radio control applications, payload is not more than 8-10 bytes and 0,5 sec is a reasonable time
for transmission and feedback (ACK) reception.
Here below the calculation equations of flight times for packet radio with payloads greater than 8Bytes:
EQ1
Tsym: Time symbol
SF: Spreading Factor from 6 to 12
BW: Bandwidth in Hz (S2 Register)
EQ2
PayloadsymbNb: Payload symbol quantity
nBytePL: Payload byte quantity
CR: coding rate from 1 to 4 (register S6)
EQ3
Tpachet: data packet total timing in seconds
12,25: Symbols quantity used on preamble
From Aurel website you can download an Excel spreadsheet that automatically calculates the flight
time radio according to selected parameters.
Data packet frame:
XTR-8LR100 is a radio modem working in packet mode and handling addresses for point-to-multipoint
networks.
Packet has a 255 bytes max length, where 247 bytes are the payload and 7 the addresses.
It's made up of:
•Preamble: it comprises 8 bytes of variable length depending on data rate, used for synchronization
purposes..
•Header: it comprises information related to the payload lengths, Code Rate, and CRC presence of
payload 16 bit
•Network_ID: every module has got a 4 bytes network ID, editable via AT command. (It’s present
only in net modality S10=1)
=BW
Tsym
SF
2
( ) ( )
+×
−× +×−×
+= 4
24
4448
8CR
SF
SFnBytePL
ceilingbNbPayloadsym
TsymbNbPayloadsymTpachet ×+= 25,12
