RSSI is not changing regardless of distance

Hello everyone,

SetUp:
I am using an AX5243. I used AX-Radio Lab to get my configurations.
I read the RSSI from the FIFO as described in the programming manual. Everything works fine - I am able to receive and send data - . I set the AX_PKT_STORE_RSSI bit, and read out the correct “chunk”. Thus I receive a RSSI. The TMGRXRSSI is 0x03.

But:
The received RSSI does not change and is allways either 0x93 or 0x92. No mather how far away from it’s communication partner the modem is? It stays 0x93 until the connection is lost.
Everything else works perfectly.

Is there something other than the PKTSTOREFLAG I have to consider?

Br

1 Like

@nikolas.zeitler

Would you share your RadioLab project ?
+
What are the code change and steps to replicate ?

Hi thank you very much for responding!

Here I am forwarding you my ax5243.h file with all the used define. And the ax5243.c with all the used algorithms. I don’t see a issue with the .c file. Since i am able to send and transceive messages.

ax5243.h (57,2 KB)
ax5243.c (31,7 KB)

e.G PktStoreFlags is used:
COMAPP_SpiWriteByte(AX5243_REG_PKTSTOREFLAGS, AX5x43_CFG_232_PKTSTOREFLAGS);

edit:
Maybe why i did not responde directly with the RadioLab + Code Changes Steps to replicate. This was done a couple of months ago. Furthermore we have to use a different development environment and hat do copy the relevant parts from the RadioLab project into our project.

Br,
Nikolas Zeitler

Hi Nikolas, I have never tried retrieving the RSSI from the FIFO. What I did, and it works, was to directly read the RSSI register (0x40) when needed. Cheers!

Hi AdAstra,

thanks for your input. Sadly this makes no difference. I performed a test comparing the RSSI from the Fifo and the RSSI from the RSSI Register (0x40). They are different. Butt still wrong (See Picture below).

image

The distance between the devices makes no difference.
Br.

@nikolas.zeitler

Can you put an Antenna IN and then remove it , to make sure that boards are working?
If the boards are close to one another then the RSSI is not gonna vary much.

See run a Tx and Rx example on 2 boards with 2 x F343. Disconnected the Antenna and we can see the RSSI going from -54 dBm to -97 dBm and at times to even -106 dBm. It is varying as expected, I dont see any problem as can be seen on the screenshot below. Can you try if you can run a similar test and display the RSSI on the LCD or via onsemi IDE?

Hi Martin,

Sorry for the delayed response.
I was quite ill and hat to get dev boards first ( we are already working with a custom pcb using your modem )

But I still got two dev-boards and testet everything. The behaviour is VERRY different. Without the antenna the RSSI still changes quite a lot or doesn’t work at all ( I can only remove the Master Antenna, without the Slave Antenna my configurations do not work )
From earlier experiences I can say, this happens also if I remove the antenna from my PCB.
But using the devboards the RSSI is quite dynamic.

I did some more digging the last couple of days trying to use the ANTRSSI2 and ANTRSSI3, sadly with no results. Since I was not able to get those results without breaking my FiFo.

But then I saw that it might be possible to compute the RSSI myself using “AGCCOUNTER " and TRK_AMPLITUDE” and then i noticed something: the AGCCOUNTER does not change at all it is allways locked at 0x68.
The TRK_AMPLITUDE does change but I did not take a deeper look into those values, since i am unsure how to work with “AX5243_REG_TRKAMPLITUDE0” and “AX5243_REG_TRKAMPLITUDE1”

The PCB looks fine. I checked the circuit board and everything looks fine. Only thing I noticed is, that we are not using the SYSCLK, but this shouldn’t be an issue.

Br
Nikolas

@nikolas.zeitler

Without the antenna the RSSI still changes quite a lot or doesn’t work at all ( I can only remove the Master Antenna, without the Slave Antenna my configurations do not work )
From earlier experiences I can say, this happens also if I remove the antenna from my PCB.
But using the devboards the RSSI is quite dynamic.

I have run simple MASTER TX ->SLAVE RX @ 915MHz GFSK 4.8kbps form our example and removed antenna on the TX side. You can see RSSI
w/o Antenna connected on RX side . Packets are still received as I you can see and LED indicator confirms that packet received as well.

and w/ Antenna connected on RX side.

But then I saw that it might be possible to compute the RSSI myself using “AGCCOUNTER " and TRK_AMPLITUDE” and then i noticed something: the AGCCOUNTER does not change at all it is allways locked at 0x68.

I have check also register AGCCOUNTER and its value changes as it should :

image

image