User's Manual

PAGE 21
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MOD090-LP
User’s Manual
OFS is the 16-bit integer Index value for this data point. The range of this index is
0 to (128 − Frequency Step Size). For example, with a step size of 1, the maximum
value of OFS is 127, but with a step size of 8, the maximum value is 120.
PEAK is an 8-bit integer representing the peak power detected at each frequency.
AVG is an 8-bit integer representing the average power detected at each
frequency.
Both the PEAK and AVG readings are a logarithmic scale, with a value of zero cor-
responding to -100 dBm and a value of 255 corresponding to -15 dBm:
Power in dBm = − (100 − ((Sample Value) / 3))
Please be aware that this scale is approximate. Linearity is poor above -20 dBm or
below -90 dBm.
Data Commands
The data commands are used to transfer data between the MOD090-LP and the host
microcontroller that is intended for RF transmission.
The MOD090-LP’s receive FIFO does not have data protection. This means that
when data is received from the RF, the host microcontroller has up to 50ms to re-
move the data from the FIFO before data corruption occurs.
The transmit FIFO does utilize data protection. If the host microcontroller attempts
to send data to the MOD090-LP while the transmit FIFO is full (indicated to the host
microcontroller using the FIFO_Full line) the data will be discarded. Please note
that in UART mode, there is no FIFO_Full line. Because the UART baud rate is much
slower than the radio’s transmit rate, transmit overow should not occur.
Data from the AP can be sent to one specic SU or broadcast to all SUs. Broadcast
MOD090-LP
5 KB Receive FIFO
8 KB Transmit FIFO
Host
Microcontroller
SPI or
UART
data has no retransmissions and is not guaranteed to reach all SUs. Data from an SU
is always sent to the AP with retransmissions. Data is divided up into blocks for RF
transmission. This division of the data allows for better interference immunity and
re-transmission performance.