Curious what your thoughts are on this vs one of the official SteamVR tracking modules[1] which use the TS3633[2]? For $10 this is an awesome hack for off the shelf components. However, for $70 + Shipping you can pick up 10 of the tracking modules which filter out noise and do accurate envelope calculation.
I'm not familiar with the SteamVR tracking modules that you linked, however from the link:
> The CM1 contains all the circuitry necessary to convert SteamVR Tracking base station infrared light into a digital output that encodes the angle of the sensor from the base station.
That implies that it's not a full location tracking solution by itself (angle only). The data sheet[0] doesn't seem to shed any further (ahem) light. Maybe I'm wrong. And I'm certainly interested in learning more. Do you have more details on the SteamVR tracking system?
Correct, it's only going to give you a signal "upon incident light from an IR source once the threshold level for light intensity has been exceeded"[0].
What you are getting in this chip is all of the work Valve and Triad have done in improving the accuracy of that envelope signal. Essentially, the accuracy in the timing of that signal == the accuracy of the position. There's a really good talk from Steam Dev Days[1] (that I was fortunate enough to attend) that gives a good overview of all the work that has gone into SteamVR tracking.
Apparently the math is complex (and proprietary). They claim they saturate a single core of an i5 processor with all of the math converting the timing signals for all of the devices to position. With the official kit, you don't do anything on the hardware side on your own with regards to figuring out position.
I was previously under the impression that the photodiodes figured out their own angular position and you received a library to convert those values into a single rectilinear position and orientation on the device. This is not the case. The photodiode ASICs basically just convert photons to voltage and clean up the signal. The official kit includes an FPGA to pack up all the sensor data and an MCU to give you an SPI interface to that data. The system is pretty much end-to-end, you mostly just get a chance to inject your own data about button clicks or what have you into the data stream from the device. SteamVR on the PC does the work of making sense of the data.
There is a huge amount of design that has to go into the sensor layout. Bad sensor layout will cause significant problems in tracking. It's extremely constraining in what you can do.
The system is designed to work with one base station. The second is only for redundancy, covering areas of the play area that are occluded for the master base station by your own body.
In contrast, Oculus uses cameras to detect IR LEDs on the device. It's kind of inside out from SteamVR. They have to them do image processing on the PC to get the angular position with regards to the camera of each LED. SteamVR just has to convert timing values into laser emitter motor positions. Once you get to that point, they are pretty much the same, having to compute position and orientation from that data. It's just a lot cheaper for SteamVR to acquire that data.
It also means that adding more cameras to Oculus adds to the workload, whereas adding base stations to SteamVR does nothing to the PC. Both will increase workload to add more devices, but it's negligible compared to the image processing Oculus has to do. Oculus' system is fundamentally unscalable. SteamVR is fundamentally scalable.
We've officially been told that the SteamVR information is not confidential. There is a lot, so if you have any questions, find my email in my profile and just send me a message.
Thanks! I actually haven't seen those, they look pretty good, basically replace the custom schematics I needed to build.
The timing calculation still needs to be done somewhere though, I wish there was a module that would do it internally and just publish the timing numbers - that would be more scalable and then even Arduino would be able to handle several sensors.
From what I understand, the official kit includes software for calibrating a specific configuration of sensors in fixed relation to each other and figuring out the timing parameters. Guess I find out for sure tomorrow!
Yeah, you've basically done all the hard work. I just ordered a batch of these to see if I can get it working. I've been wanting to hack on this since they came out. Thanks for the inspiration!
> The CM1 contains all the circuitry necessary to convert SteamVR Tracking base station infrared light into a digital output that encodes the angle of the sensor from the base station.
That implies that it's not a full location tracking solution by itself (angle only). The data sheet[0] doesn't seem to shed any further (ahem) light. Maybe I'm wrong. And I'm certainly interested in learning more. Do you have more details on the SteamVR tracking system?
[0] https://www.triadsemi.com/download/16501/