Pibrella i2c connector


#1

There is a breakout location on the Pibrella board for a connector for I2C which I am assuming is a pass through for the I2C connectors on the GPIO along with the appropriate ground and 3V3 source.

  1. Am I correct in this assumption?
  2. Is the 3V3 coming from pin 1 or 17?
  3. what is the connector that this breakout was intended for, it is not for standard pin outs, if you have a model number or a link to a page to purchase it would be very helpful.

I am trying to use the Pibrella along with an I2C sensor. I think the addition of a I2C port would really increase the utility of the pibrella.


#2

It seems to me, my dearest sir, you’ve stumbled on a mystery.
To figure out what this is for, a brief lesson in history.

I’d say it was just a few years hence.
When Flotilla specs were on the fence.
And Pibrella it was on the brink.
Of hitting shops, we had a think.
And tossed upon its boarded edge.
The connector choice t’was in our heads.

But it turned out Flotilla was delayed.
As perfections, changes and decisions made.
So never did it find a use.
And now you’ve found an end that’s loose.
This is a pretty poor excuse.
For a poem, it’s quite obtuse.
But if you’ll read just one more verse.
I’ll give you a TLDR, far more terse.

The 3V3 comes from the Pi. It doesn’t really matter where, but I could look it up if you’re curious. The connector is, in fact, a very early choice of Flotilla connector, with the idea that a Flotilla module could be connected to the Pibrella to extend it with extra sensors. So that’s why it’s an unconventional pinout and landing choice.

Unfortunately we updated Flotilla to use 5V for technical reasons, so you wont be able to hack Flotilla modules onto it, but you can use it for I2C devices that run at 3v3. The Pi has onboard pull-ups, so it should be simple enough.

I think it’s a 0.1inch pitch landing, so any 4-pin connector with 0.1inch pitch should work. I’m not sure where the best place for you to pick one up might be, though!

Alternatively, you could just solder wires right on, maybe the female end of a group of 4 female->male jumper jerky wires.

Okay… even the TLDR was long!


#3

:-) thank you! That makes a lot of sense to me. And I liked the poem!

As for the curiosity on the pin source of the 3v3 (please keep in mind I am very new to circuits) there is a small note on http://pi.gadgetoid.com/pinout if you click on Pin 1 there is a mention about a max current draw of 50mA. This “note” is not in the 17 pin.

What got me to that site in the first place was that I was having difficulty getting a HTU21D temp/humidity sensor working using pin 1 (IOError 5 for the smbus). When I switched the (+) lead from pin 1 to pin 17 everything worked fine. Now it is very possible that something else was to blame as I am a still pretty new to this.

p.s. Had not heard of the Flotilla before, and it looks really cool. The only thing you are missing is a range finding accessory!


#4

That’s a curious finding! I’d hazard a guess that something else was wrong, since Pin 1 and Pin 17 are both driven by the Pi’s internal 3V3 regulator and basically connected internally- so they’re identical in function and supply the same current.

I wonder if your Pin 1 is simply dead… it’s not likely, but it’s not impossible.

I think we have a range finder planned, and many, many other things to boot!


#5

Very off topic, sorry, but I really liked the poem too!
(and, as a backer, the nugget of Flotilla history)