Mindboards

mattallen37 wrote:What pressure sensor are you using?

MPX5700DP

the MPX5700DP looks like the one which Dexter is using for his own pressure sensor.

doc-helmut wrote:the MPX5700DP looks like the one which Dexter is using for his own pressure sensor.

Yeah, I mentioned that way back in the beginning. But, the pics are blurred on the site, so I can't see the part number. I think that this one is different, though. Dexter's is a max of 70 PSI while mine goes up to 101.5 PSI.

1 more:
a QWERTY keyboard, with a looped-through i2c plug (optional disabled pullups )

doc-helmut wrote:1 more:
a QWERTY keyboard, with a looped-through i2c plug (optional disabled pullups )

(BTW
-OT -
is there an understandable reason why the i2c pullups have to be integrated into each single sensor, and not 1 pair of pullups for all into the NXC sensor ports...? )

I'm not sure what you mean by "looped-through I2C plug" but connecting a keyboard to the NXT has already been done: http://extremenxt.com/keyboard.html

correct, I forgot about that, I remember I saw that some time before somewhere.
By "looped through" I meant sort of "chainable" to other i2c sensors.

Over the past several years I have asked mindsensors for it a couple times. Since they didn't seem to have taken an interest in the idea, I added it to my project idea list.

I don't think you really want it to be chain-able, at least not in the way HiTechnic made the Tetrix controllers. Two NXT ports wired in parallel? Now that would be semi-practical, but why not just use a port splitter?

The reason for each sensor using pullups instead of the NXT, is probably that most (non-NXT) I2C devices are setup with pullups (either permanent or optional) on the slaves. I can't think of a technical or even a practical advantage for this practice, but there aren't many dis-advantages either (on an average I2C bus). It could also be due partly to Lego cutting costs; with each NXT kit they sell, they only ship 2 pullups (in the ultrasonic sensor) instead of 8 (if they were in each NXT sensor port).

of course a port splitter works, but the pullups on the custom sensor (keyboard, muxer, what ever) must be possible to be optional disabled.
A second plug on the sensor board (just looped-through or parallelized) would be very convenient though.
Alternatetively, if you have a series of sensors (all without any pullups on-board), you may plug a terminator (2 pullups) to the last one (like at SCSI device cables):

[NXTPORT]==[dev1]==[dev2]==[dev3]==[dev4]==[dev5]==[dev6]==[term]

By this, you may plug 2 different keyboards if one wishs (e.g., to play multiplayer games)^^

I suspect the pullups are not on the NXT so that the sensor lines can be used for other (none i2c) purposes (like analogue input as used by the Lego color sensor)...

I think you should make a LCP (Lego Communications protocol) translator. The messages that are being sent over bluetooth for example (http://www.robotappstore.com/Knowledge- ... ms/92.html) can be pretty cryptic. It might be easier to make a translator device that could plug directly into the NXT.

You could also maybe make a data logger or something. Just some thoughts.

Robotman