Old NexStar GPS motor control and hand control firmware update info:
Contrary to what's published, supposedly "non-upgradable" old NexStar GPS telescopes are able to be updated to more recent firmware by using external programmers. Early (c. 2001) NexStar GPS Motor Control boards with MC1.0 and MC2.0 do not require an expensive board replacement; rather, they can easily be flash updated with the latest MC4.06 firmware using any compatible PIC programmer (e.g. PICkit). NexStar GPS Hand Controls with the original HC1.2 firmware can also be flashed to either HC1.6 or HC2.2 using a universal programmer (e.g. TL866) with a PLCC32 adapter. Andre Paquette from AstroGeeks used to offer these firmware upgrades as a service but ceased doing so a few years ago.
Because it has been well over a decade since the NexStar GPS was discontinued, I suspect that the actual number of NexStar GPS telescopes that are still out there with the original firmware is rather low. Thus I will not be writing an extensive tutorial on firmware updating for a potentially nonexistent audience. Instead, I will simply outline the basic flashing procedure and offer to provide more detailed assistance if it should be required by someone who is still stuck with old firmware (e.g. MC1.0/MC2.0, HC1.2) and wants to update.
Andre Paquette has graciously provided the required firmware binaries which are available here: https://groups.yahoo...NexStarGPS/info in a directory named 'Andre Stuff'. Note that it is necessary to become a member of the group before the firmware files can be downloaded.
Updating early MC boards with MC versions 1.0 and 2.0 requires flashing with an external PIC programmer via the MC board's program header. The most recent/best MC firmware is mc1_0406.hex (MC4.06), which can be found in the directory shown above. A PICkit or TL866A or any other universal programmer should work, as long as it is capable of flashing PIC16F876 devices. For anyone who still has such an old MC firmware on their NexStar GPS, this procedure potentially saves them the unnecessary expense of buying a new motor control board and provides much more accurate and nearly silent tracking.
Updating a NexStar version 1.2 hand control with HC1.6/2.2 is somewhat more involved as it requires the removal of two AT49F040 PLCC32 EPROMs from the handset using a PLCC extractor and flashing them with a universal programmer via a PLCC32 adapter. However, the procedure is actually quite simple if you have the right tools. The HC firmware required is hc16_even.bin & hc16_odd.bin or hc22_even.bin & hc22_odd.bin (depending on whether the user wants to upgrade to HC1.6 or HC2.2, respectively), which can also found in the Andre Stuff directory noted above. These newer versions add some important features like compass calibration along with bug fixes.
I upgraded my NexStar GPS hand control from HC1.2 to HC2.2 using a TL866A universal programmer, although any similar type of programmer should work as long as it is compatible with AT49F040 devices. Note that no higher upgrade than HC2.2 is possible with the original NexStar GPS hand control and also that HC2.2 is the last NexStar hand control firmware which supports the very user friendly GPS north and level alignment (which was eliminated due to a lawsuit with Meade). I prefer the semi-automated GPS alignment to Celestron's more recent alignment options.
Anyone wanting to update the firmware on their old NexStar GPS is welcome to respond to this thread if they require further assistance.
Edited by 12Bass, 22 April 2018 - 06:01 PM.