Pure C Arduino

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 = ...