In transistor logic, no, it wouldn't be. The low is determined by how low the transistors can pull (usually 0.5v to 0.7v) and is not affected by much else as far as circuits go. This limit is determined by the method by which the transistors function, and their materials. (Germanium diodes can pull down to 0.2v, for example, but they're very slow). This value is actually equivalent to the voltage drop across the diode. This means a 100 mv difference would put the "high" value at about 0.8v for standard circuits.

The high side is more arbitrary, but if you go too low (read: <1.7-ish volts for high-end consumer electronics) the circuits become unstable, reporting 0 where it should be 1, and vice versa. They push it as low as they can for speed and power reasons, as you said, but 100 mV difference is less than the thermal fluctuation, even ignoring problems like crosstalk.

My biggest reason doubt this, though, is that the CPU operates at 3.3v. 3.3v USB, while not spec, would make sense, as they would have voltage-adjusting circuitry off-board. (see the RS232 port for an example of exactly this design choice in use) Choosing to lower the voltage any more than the CPU is running, simply for I/O purposes, and taking the protocol even more out of spec? Why? It won't be faster or more efficient, thanks to conversion inefficiencies.

The nspire is not a fancy, cutting-edge piece of electronics. As far as mobile ARM devices go, it's quite ordinary, and an old ordinary device at that. I just don't see TI using such futuristic technology in a device like this.

oke, thanks for explaining, i'm going to built a little regulator like that soon, not sure why they have coils? L01B L02B what are those for? is that for cleaning the signal? can i leave them out of the circuit?

I could finally identify the 2nd USB port pins on the TI-Nspire J01/Dock connector:
pin 21: USB Data+
pin 20: USB Data-

But it seems that we'll need to put some more electronic on those pins before it works:
{Image}


Source with more information:
http://tiplanet.org/forum/viewtopic.php?p=149793 (in french for now)

that means i can go and work on the circuts for the dock.

That would be most likely a voltage regulator (5v to 3.3v TTL). Well that's what I assume at least.

usb should be 100mV for the data cables, so not sure? (hope i'm correct at this one)

I am wondering what you are going to use for the dock connector? I can't seem to find anything that has the right pitch.

how do you mean like how to connect it? what kind of connector?

i also cant find any connection of usb over the dock @ 19,20,21. someone told me the rx tx are 100mV so not 5 and if i don't connect the power it might work. but the nspire software didn't recognise the calc (maybe i already broke it..)

Well thats a really hard question, I think the have no idea what they start.

if people are able to make good guns with 3D printers that can mean the end of 3D printing in a lot of countries

Looking trough the pictures That the new boards contain the RU logo


does that mean something?

I'm going to finish this thing, now we know a little more about the dock and where the usb is, i'm going to design some electronics to get support for: USB, UART, Charging and header pins for all the pins from the dock. is there anything else that should be implemented? a specific kind of chip? or if you have other suggestions. tell me

the Arduino wil reboot with every new contact that is made with it

And Thanks

I have no idea how to compile my own version.. can someone compile a kernel with support for 'screen'? to interact with my arduino.

or teach me how to do it myself.

Thanks