Light sensor calibration problems in NXT-G

[squigish]

I've found what I believe to be a bug in the NXT-G firmware, which I mentioned in a thread on nxtasy.org

There is a problem with the light sensor calibration program in NXT-G.  Calibration works in the software, and (as far as I can tell) correctly maps the 0-100% range to the raw values selected.  I can view these values using the feedback box on the NXT-G software, and if I write a program to display light sensor values, they are correctly mapped.  However, the built-in View command on the NXT does not recognize the calibration, and gives percentage values that correspond to the full range of raw values, like the sensor had never been calibrated.  

At first it seemed that the RCX light sensor was being completely unresponsive to calibration, both in the software and with the view command, but now it seems to behave just like the NXT light sensor.

I haven't experimented with calibrating the sound sensor, as it is not exactly feasible to precisely control the sound level in a classroom full of kids.

[John Field]

Hi squigish,

Thanks for your post. There was quite a bit of debate around this behavior during the development. The central question was:

How do you know if the brick has been calibrated?

To keep the user interface on the NXT simple, we wanted 'View' to either use the calibrated or raw values. The problem was that if you picked up a random NXT, there wasn't a good way to inspect the calibration from the NXT itself. So, the raw value was chosen for the 'View' functionality. However, I can certainly see why you'd want to see the calibrated value.

As a workaround, you can write your own program in NXT-G that allows students to 'View' the calibrated values.

Hope this helps.

- John