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  1. #1
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    Performance question (N70 / 6680)

    Can anyone tell me why I'm getting very poor performance from a 6680 compared to an N70 running exactly the same code? The application I'm working on is supposed to display and/or record accelerometer readings from a Bluetooth-enabled sensor device, sent over a serial link. It's possible to set the output sample rate of the device from 0-250Hz, so I've been able to experiment with different rates to see how much the phones can cope with. On the N70, it can manage sampling at around 70Hz before things start getting too slow. I was expecting the 6680 to give me similar if not identical performance, since they use the same processor (both have Python 1.3.1 installed). However, on the 6680, running the same application, it can barely reach 10Hz before the delay in displaying the readings becomes apparent. I've tried fiddling with various bits of the code, but it still results in the same situation - on the N70 it's fine, on the 6680 it's very slow. The N70 has significantly more free memory, but the 6680 still has 6 or 7MB left, so I didn't think that was the problem. The N70 does have the latest firmware installed (v5.0609.2.0.1), while the 6680 has an older version (v2.04.15), could that have something to do with it?

  2. #2
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    Re: Performance question (N70 / 6680)

    What does your application do besides read the data? How does it display it?

  3. #3
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    Re: Performance question (N70 / 6680)

    Besides reading the data, it can log it to a file either on the memory card or phone memory. This is controlled through the menu, so you can turn it on/off whenever. It does tend to slow things down slightly, but the 6680 is slow even without this turned on.

    The display is a set of 3 scrolling lines, one for each of the x,y,z accelerometer axes, with a list holding the coordinates of the points (currently the last 20 readings for each axis are stored). Each time the screen is redrawn, it reads the latest value from the device, knocks off the first (ie oldest) coord in the list, appends the newest one, then calls the line() function from the Image class with the updated coordinate list to draw the 3 lines.

    If you can suggest anything that might help I'll be happy to try it, but it's not really a major problem; I added an option to toggle the graphical interface on and off, and with it off, the 6680 can log the readings to file at the same speed as the N70. That's the real purpose of the application, the graphical bit was just nice to have.

  4. #4
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    Question Re: Performance question (N70 / 6680)

    You are using the accelerometer on N70? How? I tried to get one sisx from

    http://www.daimi.au.dk/~jespern

    but it was for 3rd edition.

    N70 is 2nd Ed FP3. Can you please tell me how to use the accelerometer on N70 with python?

  5. #5
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    Re: Performance question (N70 / 6680)

    That code is for the built-in accelerometer on the 5500. The N70 (nor the 6680) does not have a built-in accelerometer, and the original poster is asking about communications with an external Bluetooth accelerometer (which'd presumably be using a Bluetooth serial interface, like with a Bluetooth GPS module, for example).

  6. #6
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    Re: Performance question (N70 / 6680)

    ah, I understand now. although I'd never heard of an external accelerometer! I should try to get one.

    The picture turns when you turn an N70 in camera mode. I wanted to use that functionality somehow - is that a gyroscope inside the phone? Has anyone been able to make an extension for that?

    Thanks for your reply!

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