I’ve been working on a little side project. I originally wanted a case and / or a stand for my Xbee and Xbee Explorer module, so I ordered a couple from Polycase and strapped it together. It looked nice enough and attached to the back of my laptop with Velcro so it was an OK solution. Then I started getting lazy and didn’t want to lug out my laptop and everything every time I wanted to log a flight, so I went to a couple of the different on-board loggers, but never really found a solution I liked (picky, I know.) So that brings me to my little project. I have just finished the schematic, layout and specs and I have a few boards on the way.
Here’s what it is: It functions in four possible modes; logger only (you can use it as an onboard data logger without the case and additional modules,) logger plus data pass-through on the USB port (with an Xbee module attached - for when you want to log data to the microSD card AND pass it through to a PC,) stand-alone receiver / logger (with an Xbee module onboard – utilizing the onboard battery, no PC required.) So if you took the best attributes of an XBee Explorer module and combined it with a really good data logger with a battery and charger…this would be the love child.
I actually have two versions: one for those of us who like elegant solutions, and another for those who believe in extreme simplicity, but require fewer features. I call them LinqLogger, basically because they were designed to log downlinked data.
The first design consists of the following components and features:
It uses an ARM7 LPC2148 (512K user flash and a ton of GPIO pins,) includes both a USB and Barrel plug LiPO charger (MAX1555,) On/Off switch, RTC (facilitates date / time stamping of logs,) Xbee socket (pick your own or use one you already have,) external reset, and start / stop recording buttons, USB link and logging status LEDs, microSD card slot (up to 2 GB FAT 16 formatted for PILES of data)
Not only does it do a nice job of data logging, but it also has a USB mass storage device profile built in - so when you attach USB, you get a mounted drive on your PC where you can see the actual files on the SD card; nice because you don’t need a separate microSD card reader / writer.
The external battery connector makes the board a very independent data logger; you don’t need another microcontroller. It comes with SD+USB boot loader that allows the end user to tweak firmware to their project specifications. Configuration is done through an on-board configuration file, so there is no need to type in initialization commands. When the module is switched on and logging is initiated, everything received by the Xbee module is recorded.
The second (simpler) design consists of the the following components and features:
It uses an ATMega 328 (16MHz, 3.3v), USB LiPo Charger (No barrel plug – MAX1555, charging LED,) microSD card slot (up to 2 GB FAT 16 formatted for PILES of data,) no RTC, On/Off switch, simple FTDI to USB (just like Xbee Explorer,) Program / Log Switch (used only when programming the ATMega328 via an FTDI – this is done so that the USB used for charging and data pass-through is NOT used for programming.)
This model uses the basic serial STK500 boot loader which comes pre-installed so that you can tweak the firmware, but has very few additional features. The system is the equivalent of combining an OpenLog logger interfaced to an Xbee Explorer with an on-board power source and charger.
If either of these sound interesting to you feel free to drop me a line. I will be posting pictures, schematics etc., and of course it will all be available as Open Source. I have breadboarded these and they both work well. The boards and the cool little cases will both be here in the coming weeks...if anyone else wants one, I'd be willing to sell them at cost as kits or something. Any ideas you guys have for additional development are obviously welcome too!