Bob Assistant - Reference Manual
2023-04-04 - Version 1.0
25
2.5.
Frame identification header
Each type of message is identified using the byte 0 of the payload, considered as a header to decode the
rest of the frame.
Example: for the
‘report
message
’
frame, the payload is identified by the byte 0 = 0x72 (decimal = 114).
See §
III Uplink payloads (Device to LoRaWAN server)
2.6.
Peak frequency value
The
peak frequency
value is calculated using the following values.
o
BoB Assistant V2 will make 2 consecutive samplings, with 2 distinct sampling rates
o
FREQ_SAMPLING_ACC_LF = 800Hz
o
FREQ_SAMPLING_ACC_HF = 25600Hz
The FREQ_SAMPLING_ACC_LF sampling is done to observe potential drift in low frequencies with a
relatively high precision, whereas the FREQ_SAMPLING_ACC_HF allows the sampling of a large frequency
window, with less precision.
The
peak frequency
and associated
peak value
are reported using either the FREQ_SAMPLING_ACC_LF
sampling information (for frequency values from 0 to ~350Hz, with a 3,125Hz step), or the
FREQ_SAMPLING_ACC_HF (for frequency values from ~350Hz to 12800Hz, with a 100Hz step)
Note
: Due to frame size limitation implied by the LoRaWAN
TM
protocol, a compromise has been made
for the FFT values sent: 32 values are sent between 0 and 3200Hz, with a 100Hz step. Sending the full
frequency window in the FFT values (0 to 12800Hz) would make the step too wide (400Hz) and not relevant.
