[hpsdr] GPSDO with Propeller chip

[H. Gruchow]

Hi all,
just would like to update you on what I have achieved so far interfacing the M12M GPS 
timing receiver with the Parallax Propeller chip. Unfortunately I have to stop further 
development for the next three weeks because I am leaving for China and India tomorrow.

1. Received the PCB on friday and started soldering.
2. The new M12M can be powered with 3.3 Volts. So there are no power supply isssues to solve.
3. Interfaced my 10 MHz OCXO as the clock to the propeller through an 74AC74 which divides 
the 10 MHz by two.
4. Using the Viewport software checked the propeller. Everything running OK.
5. Interfaced the M12M to the propeller chip. The M12M timing receiver does not have NMEA 
output and only uses binary serial communication.
6. Wrote propeller code to establish output of the 1PPS clock to an external LED. It 
blinks once every second. Success.
7. Extended my code to establish binary serial communication. On start-up the M12M does 
not have any serial output. You have to send a comannd first before it responds.
8. Code works. M12M responding.
9. Integrated the Viewport software into my code and now I am able to see the M12M output 
on the PC. Success.

To do:
1. Convert the M12M output to ASCII and show it on the VGA screen.
2. Most difficult: Synchronize the OCXO with the 1 PPS or alternatively with 100 PPS 
(software switchable on the M12M)

If I am able to make it to there I have a GPSDO with a very simple hardware. Only the 
Propeller and some software.

Will be back on the project in three weeks.

73
Horst
DL6KBF