3D Robotics

Some details on the iPhone 4's GPS chip

People are starting to look seriously at the iPhone 4 as a robotics controller. It's got a full IMU and otherwise looks appealing. You can get all the hardware chip and sensor specs from this excellent iFixIt teardown, but here's just one example: the GPS chip.

It's a Broadcom chip and the refresh rate is "up to 2Hz". The user-accessible data is provided by the OS so the refresh rate in practice may vary, but the hardware looks pretty promising.

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  • Really? I'm currently developing an iPhone synth and writing to the DAC is incredibly easy... I haven't tried reading audio yet, but it probably isn't all that bad (although I hear you have to use high level recording APIs though, no simple reading of the ADC buffer). Even if you do have to use tricky APIs, the response has to be fairly fast for apps like Ocarina to work via the mic. The max input sample rate for the 3G is 48000 or 96000 hz (rated vs field tested) and I'm sure the output rate can go much higher (a minimum of 44100hz). 9600 baud serial would be easy at those sample rated. The only problem is the older iphones' audio inputs were a lot slower....
  • I would not trust the audio port for serial communication
  • Believe me, I know how much of a necessity going out of the box can be on engineering projects. Also, that site you linked is interesting, I was under the impression that the UART on the iPhone required a complex handshake method to activate properly... I guess not. So that really is a sweet platform for xbee based communication. Keep in mind that you could also probably do the same thing over the audio port (with a voltage converter) if you wanted to do it "apple-friendly".
  • @will y
    You right, engineers are just conforming to Apples development conditions that require code singing and such. If their job is a bit like mine (engineering technician) I often go "out of the box" to get things done. I'll bet Apple Engineers do the same, personal achievement is a great motivator (hence the odd looking patent applications).

    I ran across this for interest sake. Combo with an Xbee setup you could shoot data back and fourth!
  • I only wish the UART was available without jailbreaking...
  • and the iphone has an UART for communication!
    no problem causing USB port
  • @Paul G
    The iPhone navigation works just fine moving 70m/h in a car, and it works on an airplane as well...
    @Ryan Fraser
    Honestly, I think the apple engineers don't really try all that hard to lock it down. I recall a while back when the engineers submitted some diagrams to the patent office, a couple of the icons on the iphone's screen were jailbreak-only apps, which means the engineers were using jailbroken devices.
    I also agree with you when you say that iOS is a pleasure to develop for, xCode is by far my favorite dev environment and it is one of my top reasons to use a mac. Nothing comes close, I can code many times faster in xcode than in just a plaintext environment or even a nice, organized environment like the arduino IDE.
  • I have to say after hacking firmware since the 80's digital Cable boxes are the most locked down.
    My AR drone is waaaaay easier to fly with the iPad than my best 450 heli and a traditional tx. The ballistics are great and using a WIFI repeater I don't get nearly as manny drop-out as the 2.4 ghz tx.
    IOS is a pleasure to develop for, even in an open source environment.
    Might be kind of cool to have one IMU that you could just pair with what-ever machine you happen to be operating.
  • The problem isnt going to be in the sensors but what the software was meant to do. Its meant to "see" you rolling the phone while standing, not a flying vehicle at up to 100+ mph or even constantly moving at ~30 mph. That is a world of difference in the filter. Also the filter is going to be tuned to the expected turn rates, something aircraft are going to easily exceed unless flown very gently. The fact it controls the AR drone is completely irrelevant, its sitting in the persons hand not in the drone.
  • Yes, it has a 3-axis magnetometer for the compass function. I can't recall if the API lets you get raw/uncorrected magnetic readings out - probably not.
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