The internal Bluetooth modules behave really well. No ugly cards sticking out, very low power consumption and adequate speed. Some improvements would be automatic reception of items in the Inbox, which should not affect battery life at all. Also, there are some sporadic restarts which are probably due to a buffer overflow in the NewtonScript adaption layer. Otherwise, I'd say that this was definitely a very successful hardware and software hack!
My Newton's case that is. It seems that the current wiring is more or less ok so I screwed everything back together. The Bluetooth module is powered when the Newton is on, and it's off otherwise. I still needed to figure out a reset method for the module since the two power lines are independent. There is this practical serial channel 3 select signal on the internal J6 connector which works nicely as a reset line. Now whenever the Newton reboots or is powered up, I reset the module. Power consumption is great, when active, the total is always under 100mA.
An alternative to this would be to power the module all the time and use a voltage regulator to get the 1.8V out of the permantently on 3.3V line. Maybe another day :)
But there is still a Heisenbug in the whole setup. I'm not exactly sure if the channel 3 is up to speed or if I really should get the RTS/CTS handshake working, for now I have to use a Wait(1) after each HCI packet. That's a minimal overhead. Would be nice though to know what's going wrong.
The switched 3.3V line works. I hope it doesn't cause any long term problems. Now the module is powered whenever the Newton is switched on. It takes under 10ms for the module to get into stable state, so switching it on and off is not really a problem.
Somebody with the skills to solder the dongle killer should be able to wire the BT module as well. Of course, a ready made module like the SER-001 would be much nicer!
The problem of the module sucking too much power when the Newton is switched off turned out to be quite interesting. The 1.8V power used for the module core is turned off when the Newton is off. But the 3.3V for the I/O lines and the memory is still on. This causes the module to go into some weird state where it drains about 40-50mA. Now I've got to either find a 3.3V source which is also switched off, or a 1.8V source which is constantly on. There is already a candidate for the switched 3.3V source: The power supply for the PCMCIA slots...
... a bit too much power. The Bluetooth module is supposed to draw only 12mW, but it drained my (admittedly very worn out) rechargable battery pack in 10 hours. And this while the Newton is off. Frank Gruendel has measured that the Newton draws about 1mA when off, which probably comes to around 5mW. Clearly, something is wrong. But after Reading The Fine Manual - which always seems to be a good idea, if you find it in the packing material -, I noticed that the RX and CTS lines need a 1k resistor. I'm now letting one Newton run down it's battery while switched on, and another one switched off but with the module sans RX and CTS lines installed. This should give me an idea how much energy my battery packs still holds and how much the module will draw.
In the worst case, I'd have to add a switch. Ideally however, this problem (if it still exists after adding the resistors) should be solved by controlling the power to the module via the DTR line. Unfortunately, I don't have neither the tools nor the skill to build something myself - it's already quite astonishing that I got this far!
The final setup I'm planning to use also requires a bit of Newton case modding. The antenna should stick out of the case a bit because the case is shielded from the inside with some sort of metal layer. I scratched some of that off in an area where the module sits, and the range is actually quite good. The antenna is now there where the plastic cover for the SER-001 (or modem or audio-in or ...) was. Not too attractive, but hidden behind the port door all the time. A bit epoxy modelling might take care of this later. For now I'm enjoying the first Newton with a built-in Bluetooth module, surfing the web wirelessly!