I2C...

[EBo]

While taking a break from packing for the trip I started taking a look
at the MBP085. It turns out the BMP085 runs I2C, which means that both
the mini and classic loggers should have I2C already implemented. About
the only thing that probably needs to be done is to break out the I2C
pins so other devices can be chained on the bus. Also, I need to check
that the software is sufficiently abstracted to query and service
multiple devices.

So, I think I am probably good to go with little or now tweaking of the
original design. I will have to verify this, but it is looking hopeful.

EBo --

[Steve Chamberlin]

Cool! Yeah, I think you'd have no trouble adding additional parts to the I2C bus. On the Classic the I2C pins are brought to a header for the BMP085 breakout board. You could build some kind of adapter board that plugs in there, with your extra parts as well as a socket for the BMP085. Or you could design a modified Classic board that brings the I2C pins out to a new header, and maybe some other general I/Os too. If everyone agrees with the new layout, I'd have no problems making it the new "official" version of the Classic, since the current version has an installed base of only 1 (me) and there's no current inventory of Classic PCBs either.

If you're making a custom version of the Mini, it would be harder to squeeze in an I2C header. You might be able to do it with the existing layout, but you might need to eliminate some other parts, eliminate the lanyard tie-hole, or make the board bigger.

I also didn't mean to imply that people aren't allowed to change the Mini hardware design. It's an open-source project, so of course people are free to do whatever they want. If you're making a Mini variant for your own use, then there's certainly no problem in changing the board layout or hardware. My concern is mainly to avoid proliferation of incompatible versions, with some people using the original Mini, some people using variant A, some people using variant B, and all requiring different software or different expansion boards. Already this may become a problem, because the Bluetooth option that Chris is working on is based on a revised Mini board using I/O headers not present on the standard Mini. This may be an issue if other people with the standard Mini want to use the BT design.

Blah blah blah, basically what I mean is that there's value in keeping a standard base design, because any software/hardware add-ons to that base design could be used by everyone. But if some variant proves so useful that it becomes more popular than the official base design, then it should become the new official design, and I'm OK with that too. Or if there's a compelling reason there should be more than 2 official base designs, then that's OK too. But it's probably premature to speculate too much until more people actually have a Logger in their hands to play with. Hurry up, PCBs! :-)

Steve

[EBo]

I had not interpreted your comments on nixing what I was looking at
doing. I do agree that you need to manage the complexity of what to
support and how...

I'm off this week at a conference and it will be at least a week before
I can seriously look into this, and realistically after the end of my
internship (which ends mid Nov).

Thinking WAY ahead, I would suggest rethinking the classic version as
prototype breakout board for other variants. If the Classic was
redesigned with most, if not all, of the pins broken out, then you could
set something up like the Make Microcontroller or the Arduino. Then
people could use that as a proto board and then simplify the design down
to something like the mini. Just a thought...

more later,

EBo --