Home
2010-03-16 Status Update | Print |
Written by Akiba   
Tuesday, 16 March 2010

Greetings everyone. I have some good news and bad news. The bad news is the shop is delayed again. Just when I finished my taxes and thought I was clear to go, I got an email from my antenna supplier that my shipment was delayed due to stock issues. Although its possible to open the shop without antennas, I was hoping to be able to have all the components necessary for a WSN node so that people can order things in one shipment. It's kind of petty, but since its my first shop opening, I wanted it to be fairly complete.

Since the shipment was delayed, I decided that it also gave me a chance to do some last minute product tweaks as well. I had a few people pre-order my boards and got some really good feedback from them. One of the problems was that once people put the MCU and radio boards together, the first thing they do is take it out for a range test. The problem is that the MCU board was originally designed just for development and my assumption was that people would be using it tethered to a power source (ie: USB). Actually, the original concept was for it to be an extensible version of the Atmel Raven USB stick which I found very useful, but horrible to interface circuits to. Because of this design decision, there is no battery holder or circuitry on the MCU boards. 

After I realized that people would be using the boards in this way, I re-designed the MCU boards with a battery case and power conditioning hardware to maintain constant voltage as the battery drains. I was going to introduce that board as a version bump later on. But due to the delay, I decided that I would start off with the battery version of the MCU board instead. This means that I have to scrap the original boards. Actually, I’m going try and salvage as much as I can from them and probably donate the rest to Tokyo Hackerspace for microcontroller classes. In my opinion, the battery-based boards reflect the actual usage much better and allow for both development and real-world testing.

The other tweak I’m making to the product line will be that the RF connectors on all my radio boards will be changed from SMA to RP-SMA. The reason is that RP-SMA connectors are prevalent in antennas for the unlicensed bands. The whole RF connector situation is a complete mess with SMA-P, SMA-J, RP-SMA-P, and RP-SMA-J.Don't even get me started on TNC vs RP-TNC connectors.

Most dev boards ship out with SMA connectors since its easier to connect them to test equipment for evaluation purposes. However I noticed that the people I’m talking to that are interested in my platform or are actually using it are not doing test and evaluation but are using them straight out of the box. To get them to work, they’re either needing to buy SMA to RP-SMA adapters or locating a dwindling supply of antennas with SMA connectors on them. Although I’ll be stocking the adapters, I don’t want to force people to buy them just to use the boards. The adapters themselves are quite expensive and I figure people that will need the SMA connectors will be in the minority. Hence, I decided to change all the connectors on my boards to RP-SMA. People that need SMA can use an RP-SMA-P to SMA-J adapter (see what I mean?). If that sounds like gibberish, I'll be stocking those adapters as well so you can just ask me. It’s really painful because you need to desolder all those connectors and re-tune the matching network since the RF path is changing. However that’s the price of an incorrect assumption in my original design decisions.

Sorry about all the delays and am getting a very quick lesson in the trials and tribulations of starting up a hardware manufacturing operation, even on a scale like mine. There is definitely much more to it than meets the eyes to get a product released and in hardware, things take a lot longer than in software. I've also learned that an extraordinary amount of attention to detail is required for both functional and manufacturability requirements. And of course, I realize that feedback is very important.

For those that bought the pre-sale boards (you know who you are), please contact me and we can work out a trade or heavy discount to upgrade you to the modified boards.

As for everyone else, once I get the shop open, I’m going to write a nice, long article on the hits and misses of my decisions and actions leading up to the shop opening. I made some really good decisions and some really bad ones and hopefully other people won’t need to make the same mistakes :)

Hits: 3269
Trackback(0)
Comments (7)Add Comment
RP-SMA vs SMA
written by Mariano Alvira, March 16, 2010
That's a good point about the RP-SMA. I've been using SMA on my stuff (for testing) but it makes "sense" that RP-SMA would be a better choice from a product point of view.

I like how the FCC mandate for "use something non-standard" has effectively standardized that connector: it's the standard non-standard connector.
report abuse
vote down
vote up
Votes: +0
...
written by Akiba, March 17, 2010
Ha ha ha...I actually agonized over the decision. Its going to be painful to change all those connectors and re-tune the boards. I think its the right decision though.

There just aren't that many SMA antennas anymore to justify having the connector on the boards. The only reason I was using them on my boards was for testing on my network analyzer. But in actual usage, I'm almost always using an SMA-P to RPSMA-J adapter. And yes, that's confusing as hell! I still get the names mangled and I've been doing this for quite a while now.
report abuse
vote down
vote up
Votes: +0
...
written by Conn Clark, March 17, 2010
The reason that a lot of eval boards ship with Regular SMA connectors is they avoid being classified as a product for end use as they cannot comply with fcc rules. As "development tools"/"eval boards" they can be sold without fcc certification. They are allowed to do this because they are intended to be used under controlled situations (in a test lab).

I have a funny story dealing with the fcc's mandate of a non-standard connector. At the company I was working at we were just trying to certify our second 2.4GHz product. We used a RP TNC connector for our first 2.4GHz product and were planning to do the same with our second product. When we sent the prototype off to be certified we were informed by the testing house that it wouldn't pass due to emissions and the connector was not unique enough. They explained to us the fcc was interpreting the rule as "If it can be found in a catalog or is advertised as being for sale it is standard and cannot be used". While we were redesigning the PA section to fit under a shield we had endless grief for 6 months trying to find a new connector. We met with one antenna maker's rep and he said they were working on a new connector to address the issue because a lot of people were asking for new type. He then said he would get us dimensions so we could start designing it into our product. Two weeks later we met with him again and he showed us the connector drawing listed in their new catalog.

Fortunately for us the whole industry was up in arms about this interpretation of the rule. Lots of companies had called their congressmen. Finally the FCC changed their interpretation.
report abuse
vote down
vote up
Votes: +0
...
written by Akiba, March 17, 2010
Ha ha ha...great story. Can't believe the FCC required people to use a connector that couldn't be found...
report abuse
vote down
vote up
Votes: +0
...
written by Akiba, March 17, 2010
I'm now re-thinking the choice of having a default connector. I might make it so that people can choose their antenna option from the webshop. My boards have three possibilities: on-board SMD antenna, SMA, and RP-SMA. It might be better to let people choose their default antenna from the webshop instead. It's more work though since the tuning parameters change based on the option. I'm going to need to think about this one more...

argh...decisions decisions...
report abuse
vote down
vote up
Votes: +0
Batteries
written by aevin (not logged in), March 19, 2010
I noticed you mentioned a redesign of your boards to also include battery holders. What kind of battery/-ies do you plan to use? Will it be regulated og unregulated? I'm just curious.

(I'm sorry if I'm giving you more decisions... hehe)
report abuse
vote down
vote up
Votes: +0
...
written by Akiba, March 19, 2010
I'm including a 2-AA battery holder and a boost converter to maintain constant 3.3V output. It's the same circuit I'm using in the chibi boards. It's quite a handy little circuit...
report abuse
vote down
vote up
Votes: +0

Write comment

busy
  No Comments.

Discuss...
< Prev   Next >

Login






Lost Password?
No account yet? Register

Contact

Feel free to email me:

Contact