Well I can confirm it is an issue with the FX firmware.
Again I went back and tested between LimeSuite 7.12 and 7.06.
I’m using a fairly long (3m) quality (expensive) USB3 cable and an external power supply.
When I flash FW 1.3 / GW 2.8 all is fine.
Estimated reference clock 30.7196 MHz
Reference clock 30.720 MHz
Device name: LimeSDR-USB
Expansion name: UNSUPPORTED
Firmware version: 3
Hardware version: 4
Protocol version: 1
Gateware version: 2
Gateware revision: 8
Gateware target: LimeSDR-USB
Serial number: 0x9060b00543114
Free connection... OK
Then I just reflash FW 1.4 from the 7.12:
LimeUtil --fw=/usr/share/LimeSuite/images/17.12/LimeSDR-USB_HW_1.4_r4.0.img
Then I loose the data from the gateware:
Device name: LimeSDR-USB
Expansion name: UNSUPPORTED
Firmware version: 4
Hardware version: 4
Protocol version: 1
Gateware version: 0
Gateware revision: 0
Gateware target: UNKNOWN
Serial number: 0x9060b00543114
Free connection... OK
When I flash FW1.3 again with
LimeUtil --fw=/usr/share/LimeSuite/images/17.12/LimeSDR-USB_HW_1.3_r3.0.img
Everything is back to normal! So the Gateware was fine all the time. It is just the FX3 that is unable to communicate apparently.
I also noticed that apparently FW1.4 brings speed improvements as this is what the LimeUtil --timing shows:
FW1.3:
Timing basic operations:
>>> SPI write register: 127.813 us
>>> SPI read register: 128.391 us
>>> TSP NCO setting: 899.124 us
>>> RFE gain setting: 127.471 us
>>> TRF gain setting: 255.421 us
Timing tuning operations:
>>> CGEN PLL tuning: 9.16322 ms
>>> RF PLL tuning: 16.8677 ms
And FW1.4:
Timing basic operations:
>>> SPI write register: 80.0478 us
>>> SPI read register: 79.9844 us
>>> TSP NCO setting: 401.31 us
>>> RFE gain setting: 80.1003 us
>>> TRF gain setting: 159.992 us
Timing tuning operations:
>>> CGEN PLL tuning: 1.21116 ms
>>> RF PLL tuning: 3.89895 ms
Can someone from LimeSDR confirm there are possible issues here?
As still this used to work with FW1.4 and now it fails permanently.
Can something have degraded?