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Sunday, 20 July 2014

Nokia 3310 scope experiments part 1

Continuing with the nokia 3310 display experiments, I wanted to try out if visualizing signals with this display could be any useful. For that purpose I wanted to build a simple scope with Arduino. I simply configured the ADC, used the internal 1.1 V reference voltage, configured the analog comparator as a trigger and tried to visualize the incoming samples. All of this has been done using the libpca and the following simple sketch. 



So far, with enough accuracy I did some experiments with signals up to 8 kHz. I don't want to go into details at the moment especially that I consider this project as a work in progress. The ADC has been fed with a sine signal generated using Audacity. The quality of the measurement strictly depends on the ADC frequency. A couple of pictures bellow:


1kHz, sampled with prescaler = 4

2 kHz, prescaler = 4, visible trigger jitter

... same signal, bigger amplitude
 
4 kHz, prescaler = 4
 
6 kHz, prescaler = 4, very distorted

800 Hz, prescaler = 4, visible distortions

800 Hz, prescaler = 32, a lot better quality