There is a global positioning system chip on LimeSDR-XTRX board.
Unfortunately, I did not find any suitable functions in the API to work with this chip.
Please tell me how to work with this chip from C++ code in Linux.
At this moment the GPS chip is not reachable. There is going to be a FPGA gateware update, which will expose GNSS messages through UART.
Will the one pulse per second be tied into the timing logic to allow for real synchronization of the board to real time (what we in the military tactical radio community call System Time)?
Tagging @VytautasB for comment.
Hi @N0YKG,
currently I am planning exposing serial port for software to be able receive/send NMEA messages.
At the moment there are no plans to change current sample synchronization logic at hardware level (which does not use PPS) but you are welcome to express your application needs and we can consider adding such functionality.
Regards,
Vytautas
It’s more just curiosity than anything else - I’ve been involved in the design of high-dollar SDR systems, and in standards for military SDR. All the professional grade devices (e.g. USRP) have the ability to use the 1PPS to sync the hardware. That allows for multiple units to be synchronized to a very high degree, and allows for TDMA and frequency hopping systems to sync based on absolute time rather than trying to sync to a carrier (important in low probability of intercept systems - you don’t want to have to radiate to synchronize, unless you really like eating HARMs).
However, I seriously doubt anybody is going to try to implement any of the military grade waveforms on this hardware, so that really leaves only synchronizing multiple LimeSDR for phase-coherent operation.