|Re: WP 34s and USB - more I/O possible? (edited)|
Message #8 Posted by Marcus von Cube, Germany on 27 June 2011, 4:55 p.m.,
in response to message #7 by Gerry Schultz
All the smart things are integrated into the "cable" made by FTDI. This cable is, in effect, a tiny controller chip built into the USB plug. So you need the "proper" cable which will cost you around $20. A standard USB cable will not do!
I just made a 1:1 connection of the 3V serial I/O pins inside the calculator to the stereo jack. No magic involved on my side.
In my opinion it makes the most sense to have a 34s share info with a PC via USB and use the PC application to move user programs between 34ses. I know it's an extra step to move 'stuff' but it might simplify the initial software implementation.
Both will be possible. I plan to just make the protocols totally symmetric so that it doesn't matter if one of the devices is the emulator running on the PC, making use of the USB or HP's cable, or if it is another 34S.
You will be able to connect:
A/ two 34Ses with a cross over cable,
B/ two 34Ses with two HP cables and a null modem,
C/ a 34S to the emulator via the USB cable as outlined above,
D/ a 34S to the emulator via HP's cable.
Option B works because the HP cable draws its power for the level converter from the calculator, not from the PC serial plug. It's a bad idea to leave the cable connected to the 34S or 20b/30b while not in use because it will drain the battery at a rate of 4mA even with the calculator apparently turned off.
Edited: 28 June 2011, 2:51 a.m.