BME280 + Differential I2C Bus Extender breakout pins offset

[OzFalcon]

I am surprised the BME280 Qwiic sensor module does not match the pins/mounting holes
on the Differential I2C Bus Extender. While the BME280+ENS160 Qwiic sensor module does.
Was this just an oversight or was there some other reason for not lining up?

ie. So the module can be piggybacked onto the extender.

[OzFalcon]

[SparkFro]

The Qwiic standard specifies a few things:

• 1x1 inch board (if possible, obviously the Qwiic Bus needs to be bigger)
• Mounting holes in the corners
• 2x Qwiic connectors, on opposite sides of the board
• At least 4x PTH pads on an adjacent side, in the order GND → 3V3 → SDA → SCL
• A few other details that I’m not remembering right now

It does not specify the position of the PTH pads, other than being on an edge adjacent to the Qwiic connectors and the pad order for the I2C and power connections. Other pads are often broken out, like additional data pins if using SPI, address selection, interrupts, etc. An effort is commonly made to make the pads centered on the board, so if one board has an even number of pads, and another has an odd number, the I2C pads won’t align.

I agree it would be nice if the I2C pads always aligned with each other, but the current Qwiic standard doesn’t specify a standard location for those pads. I believe the recommendation is to use the mounting holes and standoffs, then a short Qwiic cable to connect the boards.

Hope this helps!

[OzFalcon]

Thanks for the Qwiic standard. Yes the short Qwiic cable is what I was thinking.
Given that Adr/Sdo is not part of the Qwiic standard it seems to be an oversight when
Adr/Sdo could have been placed at the other end and everything lined up to piggyback.
(ie. centered the 4 Qwiic standard pins). Alot of the existing sensor modules line up.

Perhaps the layout of this module could be aligned for future production runs.
Especially given that one mounting hole was omitted (For the LED placement?)

[TS-Russell]

It just a fairly trivial situation…if we line the holes up for one specific pairing they will not be lined up for different sensors that have different pins broken-out

If it matters to you a bunch you could easily use our open-source design and board files to re-arrange/route things however you’d like; click ‘documentation’ and then ‘eagle files’ for any product on our site

But in general the engineers are focused on mission-critical aspects of board design and work on niceties if time allows

[OzFalcon]

TS-Russell
No it doesn’t matter that much, As you say it’s a fairly trivial situation.
Just a suggestion as this is probably a common entry point sensor module given it’s lower price.
I see also that there are modules with only two mounting holes. So this module could have
omitted the two holes on the PTH side and simply shifted the PTH down to line up.
Piggybacking appears more a coincidence that some things line up. Which is nice.