Gpsdo

Matt's 4th Year Project

GPSDO

This contains the design files and firmware for a GPS disciplined oscillator. It combines the frequency reference from a Ublox MAX-M8Q GPS module with a low jitter timing reference to create a very stable and accurate user defined frequency reference. There are two identical buffered clock outputs as well as a 1Hz PPS. The PPS output is used as a timing reference for synchronizing the output streams of multiple independent SDRs. There is also a command line application to view the status of the GPS and PLL live.

Lime-SDR

This folder contains various resources such as the modified gateware running on the Lime Mini's MAX10 FPGA, the design files for a small PCB to break the 0.1" header on the Lime Mini out to an SMA connector, and a setup guide.

Software

This folder contains some prototype applications written in C++ that make use of the LimeSuite LMS API.

pps_rx_sync

This program produces an output file each second that contains a header followed by a buffer of interleaved IQ samples in int16_t format. The header specifies the index of the first sample in the buffer and the index of the sample corresponding to the PPS trigger event as well as a unix timestamp for the file.

pps_tx_sync

This program transmitts a buffer of samples once per second, with the transmission occuring a predefined number of samples after the PPS event. Assuming there is some external loopback path the program also records the TX event and writes this out to file, along with the relevant metadata.

tx_testing

This program demonstrates how to succesfully specify at what sample the transmission of a buffer should occur, and how to the record the transmission in order to verify when it occured, which initially proved problematic!