I have 2 questions and that would be: When I use SSH to connect to the ADALM Pluto and see the RSSI value through using the command "cat in_voltage0_rssi", sometimes it displays 115.25dB or 51.75dB but most of the time it displays 51.75dB without any input power. What is the problem behind this? The 2nd question would be, if I want to read the RSSI value in a python script, what code should I write in the python script to read the RSSI value? Is it using " iio_channel_attr_read(iio_device_find_channel(phy, "voltage0",false), "rssi", &rssi)"?
Pluto is very sensitive so unless you have a terminator on the SMA it can pick up things in the environment and RSSI will change. Also, know that DDSs are enabled by default at boot so you may unknowingly transmitting data.
For python, if you base it off this example: https://github.com/analogdevicesinc/plutosdr_scripts/blob/master/pluto.py
The RSSI attribute could be read as:
rx = ctrl.find_channel("voltage0")
So Travis, is there a way to convert the reported RSSI read into dBm? In one of the post I have read in the forum, they did a calibration method in the following way:
Attached is the example. In the first case the delta is 17dB. In the next two cases, the delta is used to calculate the input power in dBm(-67+17=-50; -57+17=-40)
Apparently, this post mentioned that by using the input power(dBm) and the reported RSSI read (dB), I am able to use the Delta(dB) to find the next input power level in dBm.
Just only a question of clarification. Relating to the above example, the problem of using the above mentioned method is that initially a signal is being injected into the receiver of the Pluto with an input power level of -60dBm from a RF Signal Generator. It has no way of knowing the input power level of -60dBm as it is only capable of reporting it in a form of RSSI value which is in terms of Decibels(dB) and there is no way for it to report the read in dBm.
So is there really no solution or if there is, to enable it to report back to the user the power level of the received signal in dBm instead of RSSI? Is there a way to calibrate the Pluto without user intervention?
By the way, I tried terminating the Receive SMA and went to check the RSSI reading. It still displays 51.75dB.
MJohn887 said:So is there really no solution or if there is, to enable it to report back to the user the power level of the received signal in dBm instead of RSSI? Is there a way to calibrate the Pluto without user intervention?
The RSSI measurement is really not meant for this directly. You essentially need a lookup table if you want to get a dBm number. This will require instrumentation and will be specific to each Pluto.
MJohn887 said:By the way, I tried terminating the Receive SMA and went to check the RSSI reading. It still displays 51.75dB.
I cannot repeat this on my end. With a terminator, I get ~-100 dB RSSI. Make sure TX is on a different frequency or powered down.
So the RSSI varies according to different frequencies as well?