Categories: all aviation Building a Biplane bicycle gadgets misc motorcycle theater
I got some interest in the Air Data Instrument over the holiday break, so I updated a few things. In looking further into the project, I've discovered that the altitude sensor part I was using is more or less unsupported -- there's only one US distributor that carries it, and it's not one of the major ones. I noticed that when I was putting the bill of materials together the first time, but didn't think much of it.
When I checked with Digi-Key (which used to carry the part, a Bosch Sensortec BMP085), they said they completely dropped Bosch as a supplier. So... that's not encouraging. Mouser and Newark don't appear to carry anything Bosch except other people's breakout boards.
The ADI uses the BMP085 to sense altitude, and thus vertical speed. The BMP085 was discontinued some time ago, but I wasn't paying attention. Then they brought out the BMP180, which appears to be a current product, but no one (ie, not Mouser nor Digi-Key nor Newark) carries it. So although the BMP180 is available and is a drop-in replacement (possibly except for its footprint on the board, that's not obvious yet), it doesn't appear to be in a strong position.
This is, of course, not a disaster. There is a perfectly fine looking Freescale sensor (the MPL3115A2) which is available at all the major suppliers, and is a quarter the price of the BMP085, at $2.50 or so instead of $8-10. It's about the same size, and about the same power consumption, and uses a similar communication protocol.
But, it's a different part. That means a new board design, and a new code update to support it. If you've been paying attention here for a long time, you'll know that I was last actively working on the ADI in 2011. That's a bit of a gap, and I have a new embedded project I'm working on (details when it gets closer to being a real thing, but I'm currently geeking out on watchdog timers). I don't really want to switch gears and go back to the ADI to redesign it for a new part. On the other hand, it would be an excellent exercise in the kind of work I suspect embedded engineers have to deal with pretty much all the time, as old products are phased out, and new ones come in.
This was all spurred because I just ordered three ADI boards from OSH Park, which bought and consolidated BatchPCB among a few other board fab houses, and I started looking into the resources available to build the ADI. They are acceptable, but kind of minimal. (Side note to interested parties: the shared board design on OSH Park suddenly became unavailable after I ordered it and cleaned up some old projects; it'll become available again some time soon, I suspect.)
So, in the extremely limited free time I see in my immediate future, I may be spending a little bit of it playing with the MPL3115A2 to see if I can integrate it easily into the ADI design. It would be nice to have the whole bill of materials in one place.
Posted at 17:05 permanent link category: /gadgets
Categories: all aviation Building a Biplane bicycle gadgets misc motorcycle theater