I want to use a GPS module (with a PPS output) to ultimately generate a 5kHz timing signal that is phase-aligned with the PPS positive edge.
PPS-------MSP430-----DAC-------10MHz VCO-------Divider--------5kHz /\ | |(count pulses in | |between PPS edges | |inside MCU) | -------------------------------
Thus far, I can generate a stable 10MHz signal (10MHz VCO connected to an MSP430 Launchpad for control), and then I divide this 10MHz signal down to 5kHz using several 74LS90 chips.
This generates a very stable 5kHz timing signal, but the positive edge of the 5kHz signal, in the pulse of the period, is NOT aligned with the positive edge of the PPS.
How can I adjust the phase, so that the 5kHz and PPS edges are aligned?
----EDIT Thank you for your comments! Our timing error budget is 1 microsecond, so 100nanosec would be great.
I was under the impression that, IF we use a 10MHz oscillator, and control that to 10MHz with the loop, and THEN divide the result down to 5kHz, then "by default" the 5kHz would be very precise (controlling a 10MHz oscillator to within 1Hz, is 100 nanosec of timing accuracy). If I controlled the 5kHz output, and I'm off by 1Hz, then I'm off by 200 microsec (much bigger timing error). Am I correct in my thinking?