We are using the X-CTU software to try evaluate the performance of the XBEE Pro 900 OEM.
During range testing, we notice that the RSSI indicated in the X-CTU is always stuck in -81 even if we place the modules very close to each other.
However when we place the modules further apart then we start seeing the RSSI decrease in value (i.e. from -81 to -86)
does this mean that the RSSI will only indicate a value from -81 to -104?
we hope to get a feedback soon as we are in the process of deciding what module to use in our project and may drop XBEE because of this limitation.
I noticed this in my radio testing, also. After flipping thru the manual, I found this information:
“It is possible to measure the received signal strength on a device using the DB command. DB
returns the RSSI value (measured in –dBm) of the last received packet. However, this number can
be misleading. XBee-PRO 900 modules have the limitation that only RSSI values near the
sensitivity level of the radio are accurately reported. Signals received which are stronger than
approximately -85 dBm will be reported as approximately -85dBm.
The DB value can be determined in hardware using the RSSI/PWM module pin (pin 6). If the RSSI
PWM functionality is enabled (P0 command), when the module receives data, the RSSI PWM is set
to a value based on the RSSI of the received packet. This pin could potentially be connected to an
LED to indicate if the link is stable or not.”
Hope that helps!