Download
** To download everything, MinGPSDO.zip **
The design criteria for this GPSDO (GPS disciplined oscillator) were:
● Output 10MHz accurate to better than ±0.01Hz (1 part per billion)
● Use low cost components (cheapest GPS module, etc.)
● Be self monitoring so the accuracy can be guaranteed without reference to a better standard
● Require no tuning by the user
● Give feedback to the user of the current status
● If it can be done in software, do it in software
The initial design consisted of a U-blox NEO-6M GPS receiver with active antenna, a PIC16F1455 microprocessor, a 74HC04 buffer powered by a 5V wall wart. This achieved the criteria.
The current design is the same with a more elaborate power supply. It is more stable than the original, and regularly delivers better than 10MHz±1mHz.
Features
- Will accept most GPS modules. Requires 1 pulse per second and NMEA data at 9600 baud. Accepts 3.3V or 5V input
- A single LED provides status, verifies correct operation or indicate error conditions
- An optional user interface (9600 baud serial) provides second by second status, or can pass through the NMEA data.
- Dithered PWM output has steps of less than 1 microvolt, significantly better than a 16 bit DAC