Are you planning on removing the GPS handset's original flash memory IC and replacing it with SST39SF040, then using the serial port for firmware upgrading? Even if this proves unsuccessful, as mentioned above, the inability to program via the serial port may not be an issue because it seems unlikely that Celestron will be providing future firmware updates for v4 hand controls.
Please update the thread with your results.
Yes, the 39SF040 (of the newer hc) is pin compatible with the 49F040 (of the original hc).
The Reading protocol of the contents of the memory is the same for the two devices, but erasing/writing is not. The in-circuit programming part (boot block with software for upgrading) of the newer V4 software uses the 39SF040 erasing/writing protocol. The 49F040 gets fully erased with this code, including this boot block, bricking thus the hc.
When I get the parts I will program them with the programmer and then I will check in-circuit programming.
The files needed for programming the flash-eproms are the exactly 1Mbyte large bin files provided by Celestron (NXS4.22.bin, NXS 98.22.bin etc). These files have to be split to even and odd (high and low) byte files.
With WinHEX (Menu Tools -> File Tools -> Dissect -> Bytewise) its a simple procedure. WinHex asks for the source file and then outputs two files (the even is the first one). These two files are programmed into the two Flash-eprom chips. After that the chips must be inserted into the sockets on the pcb.
Edited by fmav, 07 July 2019 - 07:30 AM.