We are trying to develop a low-cost ultrasound device that can be used by inexperienced operators for health care in developing countries. We have created a low-profile optical tracking system that connects to the ultrasound probe. It outputs positional data from both the binocular camera and an on-board 9-axis IMU. The ultrasound pictures are collected on an iPhone at a frame rate of 60 per second and are time stamped to the millisecond based on the iPhone system time. The optical tracker collects positional data onto a Windows 10 laptop. We need to exactly synchronize the system time of the 2 devices (iPhone, laptop) at least to 1/10 sec and preferably to the millisecond.
Is there a way to access the precise system time on the iPhone and synchronize this with the laptop?
Full disclosure: I am an obstetrician and not an engineer. But I’m not satisfied with the story I’m getting from the developers about this. It must be possible.
We've tried pointing the laptop to the same internet clock as the iPhone, but the sync is not good enough. Maybe because of wifi latency?
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In dealing with Android devices, I've observed plenty of inaccurate - and sometimes downright
wrong - system times.
I do not have access to many iPhones, but those I have seen have accurate times.
Is the time GMT on iPhones always accurate? (E.g. speculate you could use network time or build-in ntp or use the time in GPS fixes to adjust drift; all this could occur in the platform so that applications are insulated from trying to determine the time themselves)
If the iPhone time functions do not represent a reasonable real-world time, how would you determine the real-world time?
Many phones are able to get the local time from the network provider - although I've seen that be a few seconds off here and there.
If you really need to be accurate - you can get your time from an NTP server and correct for local time using the phone's locale.
I am trying to build an internet connected touch based device using which users can do minor editing and upload photographs to web. The device will capture photographs using a USB based camera.
The question i have is where to find hardware for this custom requirement, i am looking for a touch screen around 24 inches in size.
Can any one recommend a reliable hardware vendor who supplies LCD/Capacitive based touchscreen.
I also thought to wait till launch of Windows 8, because it is built to support multi touch. I believe during launch of Win8 lot of hardware vendors will sell multi touch lcd monitors, which i can use.
If anyone can provide directions on this it will be a great help.
P.S > I am open to develop on any platform.
Look at 3M monitors and infrared frames which support 4+ touches. The old ones which come with Dell monitors suck so much. Your OS of choice is Windows 7. Also consider Flash/AIR for fast development.
How many bogomips (or any other relevant unit) can an iPhone or iPod touch deliver?
Is performance in larger applications, as on normal PCs, more limited to cache thrashing than to number of CPU instruction? Or is there some other limit?
What is a recommended total polybudget for a state-of-the-art game in a plain iPod touch (i.e. not iPhone 3GS)?
Does the ARM-11 in the iPod touch and the Samsung ARM in the iPhone have an FPU with the same performance as that of a normal PC, scaled to the core clock frequency?
The reason I'm asking is that I want to port a game with a physics engine (i'm using ODE). If you know anything else I should look out for, don't hesitate to mention it!
GLBenchmark has published a series of benchmarks for various mobile devices, including the iPhone, iPhone 3G, and iPhone 3GS. For example, the iPhone 3G appears to be capable of rendering 687,000 smooth shaded triangles per second (the best I've actually been able to get in my application is 460,000).
In regards to the CPU, the ARM processor on the iPhone has native floating point support, and even has a vector floating point unit. In comparison to a desktop, I ran a computationally intensive operation (NSDecimal addition) on both my desktop (in the iPhone simulator) and on the device (non-3G iPhone). The desktop (MacBook, white, 2.0 GHz Core 2 Duo) did 3344593 operations per second, where the iPhone did 281555. The desktop, which scored 2.64 Gflops on Xbench, was 11.88 times faster than the iPhone. Whether this means that the non-3G iPhone is capable of more than 220 Mflops would require more testing.
I was wondering what amount of time is required to convey information regarding the tilt and position (not gps) of one particular iphone to another. Could 2 iphones send and receive this information simultaneously? What about 3 iphones? I'm interested in an application that is able to simultaneously send and receive and make conditional decisions based on this information received all within a half a second-ish.
Any shot this is possible? If so, is bluetooth or wifi better?
Thanks a ton,
Jake
This is currently not possible without an intermediate server. (Without a jailbreak, which would make it possible, but extremely difficult)
I'm assuming your purpose is gaming, in which case, the latency associated with a trip to a server and back over a cellular data network, is likely to take too long for any satisfactory gaming experience. I don't believe it would be within half a second.
This will be possible via Bluetooth in the upcoming 3.0 iPhone software, but that is still under NDA, so you are not likely to be able to get any reliable performance numbers until it is released. If I were guessing, I would certainly guess that the latency associated with a direct Bluetooth connection would be FAR under half a second.
All you've got as an option right now is Wi-Fi or the Cell Network. If you use Bonjour over Wi-Fi, you'd have latencies in the milliseconds, but all the phones would have to be connected to the same access point. Take a look at the WiTap example.
It is definitely possible, you'd want to connect your peers over WiFi for best performance and reliability, but Bluetooth would be ok as long as your data packets were constrained to small sizes (< 1k). Check out this documentation and sample code to see how to access UIAccelerometer:
http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIAccelerometer_Class/Reference/UIAccelerometer.html
http://developer.apple.com/iphone/library/samplecode/AccelerometerGraph/index.html#//apple_ref/doc/uid/DTS40007410
The trick is that the update frequency is controlled in part by the systems needs, so there may be a window (while the system is attempting to update device orientation) wherein your application receives no updates.
Does anyone know what kind of range can you get from the iPhone
bluetooth? Also, would the connection be strictly one to one? I know you
can choose from a number of peers to connect to but once the connection
is established, it seems you can only transfer data between one peer? So
basically, is it possible to create some kind of "multiplayer" experience?
Just answering the range part of your question...
The 10 meter figure for class 2 devices (of which the iPhone is an example) is very much a guideline.
The range of a Bluetooth device is limited by many real world factors. The 2.4 GHz radio frequency used by Bluetooth is strongly absorbed by water. For example, consider an iPhone connected to a Bluetooth mono headset. If the headset is in one ear and the iPhone is in your trouser pocket on the opposite side of your body, then there's a lot of water between the two devices. This will often cause a significant amount of packet loss in practice (you can hear this in the audio being carried). So, in this case, the range is about one meter.
At the opposite extreme, two class 2 devices separated by nothing more than clear air can get ranges of hundreds of meters.
Other factors that influence things are:
Interference - Lots of things use 2.4 GHz. WiFi, for example can cause problems.
Antenna design - Space and cost constraints often mean that the antenna design is sub-optimal. I don't know how good the iPhone is in this respect.
Walls - Generally walls attenuate Bluetooth signals. However, sometimes they are useful reflectors.
Quality of hardware - Some chips work better than others. Even different firmware revisions of the same chip may perform differently. Different versions of the iPhone probably have (or will have) different chips in them.
Protocol - It is possible to work around poor signal quality with error correction and retransmission. Even if the iPhone SDK forces you to use a particular protocol, careful design of your application can make a difference.
So, in summary, you should probably do some real world tests.
The connection is one-to-one, but you can create an adhoc network with one of the phones acting as the master/coordinator. The other phones would route all their communication through the master/coordinator.
One device can theoretically connect to 7 devices. according to the master-slave role, the device can multiplex between each of them giving the user an impression that you are connected to all of them simultaneously. Bluetooth specification does not stop you from doing that.This is theory.
Now for the iphone, whether it can connect to to more than one device can only be answered by apple or someone who knows the iphone bluetooth API. But I am pretty sure the bluetooth chip inside iphone should be able to connect to more than one device.
Range is essentially going to be good enough for a normal sized room to be covered. It can be longer or shorter depending on environmental circumstances, but remember that bluetooth was created to implement short range connections.
A bluetooth device can be part of a piconet of eight devices, one master and up to seven slaves. The slaves cannot communicate with each other, they must talk through the master, think of a star topology with the master in the center. The iPhone SDK has a GameKit framework that can be used to create the network for multiplayer games. Go to developer.apple.com at look at the GKTank and GKRocket sample code to see how it's used. These games only support two players, but the GameKit framework supports more. Look at the app store and you will see games that have four or more players.
Hope this helps to get started.
Apple iPhone 3G has a Class 2 bluetooth module. Class 2 Bluetooth devices have a communication range of 10 meters.
At a given instance a device can connect to just one device because it follows a master/slave communication model. But still we can perform a multiplexing. So we can virtually connect to more than 1 device and by rapidly changing the connected device.
I found a good article here. It explains bluetooth very well.
According to the my knowledge, multicasting is not impossible with bluetooth. So gaining a multiplayer experience is NOT impossible.
The bluetooth in the iPhone is Class-2, with a 10-meter range, approximately.
Unfortunately I can't answer the other parts of your question.
One device can be connected up to 8 others. It all depends on the iPhone bluetooth API (which I don't know anything about), but with Bluetooth itself you could then send data to multiple devices.
I tether my iPhone to my laptop over bluetooth every day, and I seem to remember having done that at the same time as using a bluetooth headset. YMMV.
It’s the latest incarnation of Bluetooth, the wireless device-to-device technology that allows your phone to talk to headsets, car stereos, keyboards and other devices directly, without the need for a router or shared wireless network.