Dear list members, Im making measurements of received radio signal strength of micaz motes. My setup contains a transmitter and a receiver. The receiver is connected to a MIB520 board and im changing the distance between the transmitter and the receiver to get a rssi-range characteristic. I have the following "problem": i have programmed the transmitter's radio to 0dBm and -25dBm transmit power and the none the characteristic nor the values were changed significantly. I have checked that they are really programmed to different transmit power leves by checking the maximum transmit range, but the RSSI values were nearly the same in both cases. Is it possible that the RSSI calculates with the transmitter's power? I have only found this in the Chipcon CC2420 datasheet:
"CC2420 has a built-in RSSI (Received Signal Strength Indicator) giving a digital value that can be read form the 8 bit, signed 2's complement RSSI.RSSI_VAL register. The RSSI value is always averaged over 8 symbol periods (128 μs), in accordance with [1]. The RSSI_VALID status bit (Table 5) indicates when the RSSI value is valid, meaning that the receiver has been enabled for at least 8 symbol periods. The RSSI register value RSSI.RSSI_VAL can be referred to the power P at the RF pins by using the following equations: P = RSSI_VAL + RSSI_OFFSET [dBm] where the RSSI_OFFSET is found empirically during system development from the front end gain. RSSI_OFFSET is approximately �C45. E.g. if reading a value of �C20 from the RSSI register, the RF input power is approximately �C65 dBm." Thanks for your help in advance Adam Scheuring _______________________________________________ Tinyos-help mailing list [email protected] https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
