[hpsdr] GPSDO with Propeller chip

[H. Gruchow]

Hi all,
have worked yesterday and today on my Propeller GPSDO.
Achievements:
1. 1pps tick of GPS timing receiver makes an LED blink once per second
2. I can talk to the GPS receiver and send commands to it
3. The GPS receiver talks to me sending the binary Ha message full data over USB to 
Hyperterminal on the PC.
4. In Propeller I extract date, time, satellites visible, satellites tracked and the 
receiver status (2D fix, 3D fix) and send it over USB to Hyperterminal
5. Receiver status (2D fix, 3D fix, no fix) shows on external LEDs

No. 1, 2 and 3 work independent of each other in different processors (cogs) of the 
propeller chip.

Now comes the hard part to discipline the OCXO with the GPS 1pps tick.
Has somebody got some algorithms for a digital PLL and would like to share them?

The Propeller has an edge detect feature which could be triggered easily by the 1pps and 
then start to count frequency. I think this could be a way to implement some disciplining.

Who would like to jump in?

73
Horst
DL6KBF