1PPS Measurement Procedure

Enhanced PTP User Guide (UG1602)

Document ID
UG1602
Release Date
2022-10-18
Revision
1.0 English

To measure and adjust offsets using 1PPS:

  1. sfptpd should be running between master and slave servers, and should be synchronized before the 1PPS value is measured and applied.
  2. The master 1PPS output should be connected to a single slave 1PPS input.
  3. On the slave server, for a short period such as 5 minutes, observe the 1PPS mean offset value from the pps_off_mean file to identify the mean offset value. Refer to 1PPS Statistical Data for instructions on reading the 1PPS statistical data files.
  4. On all slaves on the same network segment, configure sfptpd with knowledge of the mean 1PPS offset.
    • If the initial observed 1PPS offset is a negative value, then all subsequent offsets should be added as positive values to the ptp_rx_latency option. The ptp_tx_latency option in this case should be zero.
    • If the initial observed 1PPS offset is a positive value, then all subsequent offsets should be added as positive values to the ptp_tx_latency option. The ptp_rx_latency option in this case should be zero.
  5. Continue to observe the 1PPS compensated mean offsets.
  6. Repeat steps 3-5 adding or subtracting the 1PPS mean offset (doubled) value each time to the last applied value until the observed 1PPS mean value is as close to zero as possible.