Re: ProgRock - Serial Update
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Recently I received my new ProgRock chips with updated firmware to allow serial programming. Even with GPS discipline, I couldn't attain the 1 Hz. accuracy I expected from my ProgRock, so easy editing of register 2 became necessary, hence the desire for serial capability. I purchased my ProgRock kit prior to the firmware update 1.01a, which included serial interface ability.
I've had the new chip running for several days now, interfaced to my PC via a FTDI USB to serial adapter https://www.sparkfun.com/products/12731; serial communications with the chip are now easy and reliable.
I've put a value of 2 in register 3 so the GPS derived updates to register 2 occur more frequently. However, regardless of what values I put in register 2, using GPS discipline always results in the output frequency running high by ~182Hz. I *suspect* this has something to do with a value in register 28, but in the manual for ProgRock we're told to "leave that register alone" until further information is made available concerning how to manipulate it.
Before I connected the 1PPS from the GPS receiver, I was able to achieve decent frequency accuracy by thermally connecting the 27MHz. crystal to the heat sink for the 7805 regulator & the cast aluminum housing containing the works. Once the temperature reached equilibrium, the thing worked pretty well, usually within 6-8 Hz, depending on the ambient temperature. The additional info section on frequency stability of the manual was very helpful in this.
As is stands now, the only way I've found to maintain my desired 16,686,666 Hz. output frequency using GPS discipline is to set the desired register (08) to 16,686,484 (182Hz. low). With that setting, my counter registers a very stable 16,686,665 - 16,686,666 Hz. output, which is close enough.
If anyone on the list has suggestions on how to eliminate my seemingly inherent 182Hz. error, I'd like to learn about it.
I thank those of you who've given helpful information concerning the QRP Labs equipment by dedicating your time to documenting your experiences and offering guidance to new comers such as me.
Robin Midgett K4IDC
On Wed, Feb 21, 2018 at 9:44 AM, Robin Midgett <K4IDC@...> wrote: