AvaLAN Wireless AW900mSPI-10 - Manual (Page 22)

AW900mSPI User’s Manual
PAGE 22 Technical support (650) 384-0000 www.avalanwireless.com
Byte 32 DP15 DP14 DP13 DP12 DP11 DP10 DP9 DP8
DP is the 16-bit integer number of data points in the spectrum scan. The value will
depend upon the frequency step size specified in Byte1. The next 4 data bytes will
be repeated DP times.
b7 b6 b5 b4 b3 b2 b1 b0
Byte 33 OFS7 OFS6 OFS5 OFS4 OFS3 OFS2 OFS1 OFS0
Byte 34 OFS15 OFS14 OFS13 OFS12 OFS11 OFS10 OFS9 OFS8
Byte 35 PEAK7 PEAK6 PEAK5 PEAK4 PEAK3 PEAK2 PEAK1 PEAK0
Byte 36 AVG7 AVG6 AVG5 AVG4 AVG3 AVG2 AVG1 AVG0
... Repeat DP times to read all the spectrum data
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.
XC1220
5 KB Receive FIFO
8 KB Transmit FIFO
Host
Microcontroller
SPI or
UART
Data Commands
The data commands are used to transfer data between the XC1220 and the host
microcontroller that is intended for RF transmission.