Thanks for those traces. In spite of the fact that they just show the escape sequences at the start of the dialogue they're oddly helpful.
Basically they confirm that Celestron hasn't modified too much of the WiFly dialogue. I suspect their custom firmware is mainly in aid of the special handling needed for the aux bus.
I wouldn't mind on of NexStar configurator or SkyPortal actually trying to set up a SkyQ, since I can't figure out how to coerce SkyPortal into accepting arbitraryTCP/IP configuration. I guess that's specifically to stop people like me from using it without buying a SkyQ, since it's effectively just a free rebranded SkySafari plus with the mount and alignment model for Celestron scopes built in. As I already own a copy of SkySafari I don't feel particularly guilty about trying to fake it out.
My cable is basically this:
PC Cable for NexRemote on Aux Port
but with the MAX232 replaced with one of these:
FTDI USB TTL Serial Module
. I put a SO14 74HC125 on a little breakout board and wired everything with soldered jumpers. Instead of making the cable an integral part of this assembly, I just used an RJ11 socket with trailing wires. I then shoved the whole thing in a large (1.5") adhesive-coated heatshrink tube with the RJ11 at one end and the FTDI board at the other.
This is only useful for connecting to the aux port directly. For any scope with a 'PC' port (NexStar GPS or CPC for instance) you need one of these (they are commercially available from both Celestron and a number of third parties):
PC Port Serial Cable
.
It looks like a simpler cable without the HC125 buffer will work on the NexStar 'i' series telescopes:
NexStar i Series Cable
It appears these use pin 1 on the RJ11 connector as CTS. This pin is apparently unused on the AS-GT and other equatorial mounts.
The HC125 acts as a buffer/line isolator. It disconnects the TXD line from the aux bus when RTS is deasserted. You have to set RTS high during every command and then immediately lower it to get the response from the motor control board, like controlling an RS485 half-duplex bus. It also messes with pin 6, which is labeled 'drop'. This is grounded whenever RTS is high and pulled up to 5v otherwise.
Note that TTL logic levels are reversed for serial signals: RTS is asserted at 0v and deasserted at 5v.
Unfortunately i don't think you can use the TXDEN signal from the FT232R (normally used for controlling an RS485 transceiver) as that will twiddle the bus isolator on every byte sent. If the motor control board doesn't implement the bus arbitration in hardware (and from what I've seen of the control board it's all done in a Kinetis MCU on the AVX) this might generate enough interrupts to crash or confuse it. You might be able to use it if you build in a monostable of some sort, but that's even more complicated than the cable I built.
