Thursday, December 27, 2012

Tindie, Wireless Project, Data Bus

Wireless Project

I've been working with Amplitide Shift Keying receiver and transmitter radios for a home sensor project but there are issues.

One problem is that the automatic gain circuit on the receiver puts a lower limit on baud rate (signal changes per second).

If the signal stays the same for long, the AGC sensitivity changes and starts picking up noise instead of the real carrier signal.

I've tried using Manchester code to ensure a minimum baud rate. I've also worked at transmitting square waves of two frequencies.

The latter could improve noise resistance but I haven't worked out the receiver software yet. Frankly, I'd rather just get the project working so I've ordered a pair of JeeNode transceivers from Jee Labs which are Arduino-compatible and based on the RFM12B radio.

Jee Labs has an excellent blog. I've learned a ton of interesting things from that blog in the last couple weeks since I subscribed. Highly recommended.

Christmas for Data Bus

Thanks to my very generous mother in law, I'll be soon purchasing an XBee radio pair from Radio Shack with a gift card. The radios will eventually find their way onto Data Bus for wireless telemetry and configuration.

I am still planning on entering the 2013 AVC. I may switch from the mbed platform (a ton of work but with some significant advantages). More important is improving accuracy of position estimation even at ludicrous speeds.

Assuming the same type of race next year, speed will once again be critical. Next year, 25 mph won't cut it. Will speed double again?  Or just increase significantly? Above 30 all sorts of things start to get really hard.

It's likely that I'll upgrade the chassis for improved handling. I will definitely be upgrading the motor, ESC, and battery for higher speeds.

Duratrax DRX8E (pic from Duratrax website)
I suspect 1/8th scale may be the way to go in the Peloton class, especially with the new budget options available. The Duratrax DRX8E is a 1/8 buggy roller for $200. ECX now has the 1/8 Revenge brushless buggy for $400.

I think (hope?) 1/10 scale still stands a chance, depending on the terrain. I hope so. No one makes a 1/8-scale school busy body. :)

Tindie News

I'm really excited about the Tindie Fundraisers. A couple of them are doing pretty well.

These are all designs I made for myself so I could spend less time dinking around with annoying, fiddly things, and more time getting to firmware. And, they're also as budget-friendly as I can make 'em.

Instead of just another microSD breakout board, the eeZee microSD plugs right in next to an Arduino/ATmega328P so I don't have to remember which line is MISO, MOSI, SCK, and CS. I've designed it to plug into the breadboard power strip too. And, it's designed to be 5V safe.

The eeZee Propeller is much cheaper than the PropStick but breadboardable unlike the QuickStart and I can reuse my FTDI breakout board or prop plug without taking up yet another (virtual) COM port.

The eeZee crystal means I never have to fiddle with crystals and caps on the breadboard again. just plug it in and get busy making stuff.

I figured others would benefit too while at the same time helping to supplement my meager "allowance" from "the boss" for hobby electronics. :)


  1. Thank you for doing the Tindie projects! I'm excited about them also, especially the Propeller board.

    As far as the XBees go, I'm a big proponent of the Synapse Wireless RF266 module. It is so much more powerful and programmable than the XBee, it is just amazing. They are pin compatible with XBees, but the programming is completely different (python scripting vs configuration setting only). Highly recommended.

  2. Received my Tiny breakout board this weekend--thanks!

    And I'm looking forward to reading your impressions on the JeeNode wireless boards.

  3. @Brian: Glad to hear it! Any and all input welcome.

    Meanwhile I just put up an ATtiny2313 target / breakout design on Tindie as a fundraiser.

    I'm still waiting for my RF12B's to ship from Sparkfun. Why oh why didn't I just order JeeNodes with the stock radios?! :)


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