Hypothesis - Direct USB/Bluetooth from Skywatcher Handset

[Ajhayter]

So I'd like to express this is just a theory at the moment. I'd like to try it, but I don't have the funds (to replace the handset in case I screw up) or enough small-scale soldering practice (to reduce chance of screwing up) to try this just yet. To be honest this will likely end up just one of those things that gets thought about but never put into practice as the existing solution (cables) work well enough. I'll certainly update if I get the opportunity to try this though.

We currently know that the Skywatcher handet rj12 aux port runs at RS232 voltages (+-13v). As such the cable from the handet goes to a DB9 connector, and we then use an RS232 to USB connector, or RS232 to Bluetooth adapter to connect to our devices.

However the handset itself does not run on RS232 voltages. It runs on TTL voltages (0-3v). This is then converted to RS232 (-13v,+13v) by a MAX232 chip in the handset.

As such for USB, the signal path is currently TTL 3v(Handset) > RS232 (Handset) > RJ12 > DB9 > RS232 (Adapter) > TTL 5v (Adapter) > USB

And for a bluetooth module (e.g. HC05) it is TTL 3v(Handset) > RS232 (Handset) > RJ12 > DB9 > RS232 (Adapter) > TTL 3v (Adapter) > Bluetooth

That's an awful lot of middle man.

As such I had the following idea - To tap the TTL signal inside the handset and convert that directly to a device, specifically to a HC05 bluetooth module, which runs directly off 3V, which might even fit within the handset casing.

This could potentially also be tapped and used with a TTL to USB cable.

The RX and TX lines can be easily accessed through pins 11 and 12 of the on board MAX232 converter. Then it's simply a matter of finding a suitable point on the PCB to tap for ground and 3v (Max 40mA draw)

Any more experienced electrical hobbyists around with any thoughts on this?