2014-05-25

PI4 + CW Reverse DDS Code

Online tool to make mixed mode (PI4 + CW + carrier) beacon assembler and hex files for John's, G8ACE, microwave Reverse DDS AD9851 based upon modifications of Andy's, G4JNT, original assempler file version Apr 2010. Modifications made by Steen, OZ2TG.
This webtool makes a .hex file and one single .asm file, that includes specific beacon hardware settings, the encoded PI4 message and the CW message. The .asm and .hex files are zipped for downloading. Then unzip and program the .hex file to the 16F628A in the RDDS unit. You can also use the files for a single frequency reference locked LO for a microwave transverter.

New features - version 2014-03-02
Parameter Value Notes
PI4 message     Valid characters A-Z, 0-9, <space> and /
PI4 mode PI4 is the normal mode
CW message Valid characters A-Z, 0-9, <space> and /
CW speed Letters per minute [LPM] Recommendation: 60 LPM = 12 WPM
Nominal beacon frequency GHz MHz kHz  Or LO end frequency if Pin 7 to ground
Frequency multiplier Value must be greater than zero, e.g. typically 96 for 10 GHz
DDS reference frequency MHz kHz Hz Typically 10 MHz from a GPSDO, Cs standard or Rb standard
GPS NMEA polarity 5 V logic (H)   RS-232 (L) Use RS-232 if logic level is inverted (0=high and 1=low)
GPS data type Motorola: @@Ea, NMEA: $GPRMC
GPS 1 PPS Ignore ( )   Use (H) If used the 1 PPS must be low-to-high/positive edge
GPS output time delay ms Varies with GPS receiver model and protocol
16F628A Xtal frequency 11,2896 MHz   12,288 MHz 12,288 MHz improves the S/N by 0,2 dB
  Please set all parameter values!  
       

GPS data and output time delay

If the voltage level of the GPS data is above 5 V, e.g. RS-232 using +/- 12 V, then mount a 4,7 kΩ resistor in series with the data signal.

Most GPS receivers have less than 1 s delay. But many have more than 1 s delay and some even more than 2 s delay!
Please note that the polarity of the 1 PPS, if used, is designed to use a low-to-high transition/positive edge/active high.

Bo, OZ2M, www.rudius.net/oz2m