I've been using a few WT-4 transmitters in the past years, for event coverage mostly, and was never really satisfied with it.
Despite the RP-SMA connector and a bunch of high gain antennas, it's damn slow and has a really weak TX power. It's also missing some interesting features i'd like to implement.
I took one of the WT-4 appart and did some preliminary search to find out what it's made of :
- A Marvell 400MHz VoIP oriented SoC (ARM based)
- 4MB flash (firmware)
- 16MB ram (nanya DDR sd-ram)
- 1GB buffer flash (from sandisk)
- An Atheros (AR5414 based) mini-PCI industrial WiFi module
As the SoC wasn't supported by the Linux kernel when the WT-4 was announced, I guess it's running some VXWorks crap, and will therefore be quite difficult to crack. It's just a guess yet, as I didn't find the serial I/O on the board to see its bootlog.
My first clue is about the wireless coverage. As the module is atheros based, it should be able to drive some ubiquiti networks XR card (up to 1W TX power). Still, it needs a slight hack to enable such high power, and some wirering to feed enough juice in the card (3.3v, 900mA peak) instead of 500mA on the Silex module' spec).
What I'm looking for is anyone who may already have reversed either the WT-4 itself, or the PtP USB protocol used to drive it from the DSLR.
My plan is to use some embedded boards (Marvell Kirkwood at up to 1.2GHz for instance) to enable the folowing features :
- More buffer space (8-16GB) on a fast CF or SATA SSD
- Higher offloading rate
- Higher wireless tx rate (using 802.11n adapter) OR less sensitive frequency (some ubiquiti XR cards can use alternative frequencies, very usefull on events when hundreds of wireless networks are at large on the same narrow frequency band). 180-280MHz for instance is more efficient through walls and may cover up to 500 meters indoor with no line-of-sight
- Ability to automatically resize image and apply basic batch processing to allow straight-to-www upload
- Drive an USB HSPA (3G) or CDMA modem to upload straight to the Net without a local internet access
- Optionally, forward a NMEA compliant GPS feed to the DSLR or add the location tag in the EXIF while post-processing the files (could be faster and simplier)
- Multiple USB ports to hook 2-3 DSLR to the same transmitter
- Configuration made through a web interface rather than the camera's menu (I.E. use you iPod/iPhone or any smartphone hoocked via WiFi)
- Control of the camera from the web interface or via pre-programmed scripts (e.g. take and upload 1 high res picture every minute)
- The post-processing and uploading could be done by a secondary (and fixed) module instead of an embedded one, allowing several transmitters to be hooked to it
- At last, the solution could also be purelly software and run off a netbook rather than using a specificaly designed hardware. Some sub-notebooks have a quite impressive battery life, it could be enough for our intended use.
Optionnal question, how many of you guys could be interested by such device, either to contribute to the project or eventually buy one once ready ? (I make no promises here, I'm not yet sure I will be able to make it work).
For those who may be interested, take a look at the D700 dev kit for the USB-PtP command set, and to the OpenRD client board (http://www.einfochips.com/marvell/) for the marvell kirkwood specs and potential power. Also, ubiquiti network cards (http://www.ubnt.com/products/xr1.php) are interesting for alternative frequencies and higher power in some countries allowing it.
So, who's in ?