I have been trying to upgrade the firmware on my HEQ5 SynScan V3 handset for quite a while now, in the hope of improving the mount's goto accuracy.
Not having an RS232 port on my computer, I first wired up my own cable using an FTDI USB to TTL circuit board that I had lying around from a different project.
It was a total bust - the firmware loader would never recognise the handset.
OK. I assumed TTL voltage wasn't high enough to work with the handset.
So I bought a "real" FTDI RS232 cable from ebay, and wired up the handset.
Another Failure, so I rewired, and rewired and rewired - all failed.
I investigated the RJ45 tp USB adapter that skywatcher sell - "Not able upgrade firmware" said the salesman.
Eventually a salesman from BinTel suggested I could probably use the Celestron RJ11 to DB9 cable cable since no similar cable existed for the HEQ5.
I plugged in all the pieces today and, *sigh*, got another "Handset not Found" error. For some reason, I pressed the Handset button in the firmware loader again - and it found it!!
But when I went to upload the firmware, i discovered V4 firmware was only for V4 hardware -makes sense. I found the V 3 firmware and stated the upgade - looking good...
..until it failed at 1.4% and said I needed to power cycle the hand set
I retried a number of times with a similar result.
In windows device manager (I'm in Win 10) I could see the COM port was defaulting to 9600 bps.
I dropped this to 2400 and tried again.
I got the same error message, but i noticed the handset screen had LO printed on the Right hand side.
without power cycling the handset, i just tried again and VOILA! it loaded - slowly, but it loaded.
Now the weather forecast in Melbourne is for rain for the next 5 days...
If anyone is facing similar problems with their firmware update, drop me a line and we can see if there's a way to share my cable (once all these restrictions are over!).