[srsran-users] Questions about using gpsdo

[董宝鳞]

Dear team


When using the GPS signal as a synchronization signal, I found that the judgment of the sensor reading in the code may be wrong. The specific problem is that the sensor can actually be read successfully and stored, but the code judgment result is that the sensor reading is unsuccessful. The output of the console :
```
Lower PHY in quad executor mode.


--== srsRAN gNB (commit 374200dee) ==--


Connecting to AMF on 192.168.1.20:38412
Available radio types: uhd.
[INFO] [UHD] linux; GNU C++ version 10.5.0; Boost_107400; UHD_4.4.0.HEAD-0-g5fac246b
[INFO] [LOGGING] Fastpath logging disabled at runtime.
Making USRP object with args 'type=b200,num_recv_frames=64,num_send_frames=64'
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Detecting internal GPSDO.... 
[INFO] [GPS] Found an internal GPSDO: LC_XO, Firmware Rev 0.929b
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Setting master clock rate selection to 'automatic'.
[INFO] [B200] Asking for clock rate 16.000000 MHz... 
[INFO] [B200] Actually got clock rate 16.000000 MHz.
[INFO] [MULTI_USRP] Setting master clock rate selection to 'manual'.
[INFO] [B200] Asking for clock rate 23.040000 MHz... 
[INFO] [B200] Actually got clock rate 23.040000 MHz.
Error: failed to read sensors.
external clock is ready!
Cell pci=1, bw=20 MHz, dl_arfcn=647000 (n78), dl_freq=3705.0 MHz, dl_ssb_arfcn=646944, ul_freq=3705.0 MHz


==== gNodeB started ===
Type <t> to view trace
Late: 0; Underflow: 2; Overflow: 0;
Late: 0; Underflow: 2; Overflow: 0;
Late: 0; Underflow: 1; Overflow: 0;
Late: 0; Underflow: 1; Overflow: 0;



```
I tried to modify the code. USRP can be successfully set to GPS time, but after setting it to GPS time, there will be a serious delay problem.
```
Lower PHY in quad executor mode.


--== srsRAN gNB (commit 374200dee) ==--


Connecting to AMF on 192.168.1.20:38412
Available radio types: uhd.
Making USRP object with args 'type=b200,num_recv_frames=64,num_send_frames=64'
[INFO] [UHD] linux; GNU C++ version 10.5.0; Boost_107400; UHD_4.4.0.HEAD-0-g5fac246b
[INFO] [LOGGING] Fastpath logging disabled at runtime.
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Detecting internal GPSDO.... 
[INFO] [GPS] Found an internal GPSDO: LC_XO, Firmware Rev 0.929b
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Performing register loopback test... 
[INFO] [B200] Register loopback test passed
[INFO] [B200] Setting master clock rate selection to 'automatic'.
[INFO] [B200] Asking for clock rate 16.000000 MHz... 
[INFO] [B200] Actually got clock rate 16.000000 MHz.
[INFO] [MULTI_USRP] Setting master clock rate selection to 'manual'.
[INFO] [B200] Asking for clock rate 23.040000 MHz... 
[INFO] [B200] Actually got clock rate 23.040000 MHz.
gps_gpgga 
gps_gprmc 
gps_time 
gps_locked 
gps_servo 
ref_locked 
Setting USRP time to 1712542143.0s
[INFO] [MULTI_USRP]     1) catch time transition at pps edge
[INFO] [MULTI_USRP]     2) set times next pps (synchronously)
external clock is ready!
Cell pci=1, bw=20 MHz, dl_arfcn=647000 (n78), dl_freq=3705.0 MHz, dl_ssb_arfcn=646944, ul_freq=3705.0 MHz


==== gNodeB started ===
Type <t> to view trace
Error: exceeded maximum number of timed out transmissions.
Late: 4981; Underflow: 1; Overflow: 0;
```

Radio head: USRP B210OS: Ubuntu  22.04.4 LTSuhd version：4.4.0 The configuration file and my modified code have been placed in the attachment (Only the "set_time_to_gps_time()" function in the "radio_uhd_impl.cpp" file has been modified).Thank you!









董宝鳞

北京邮电大学/研究生/信息与通信工程学院



北京




 
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