| ??? 09/14/07 14:23 Modified: 09/14/07 14:25 Read: times |
#144622 - That is all?? Responding to: ???'s previous message |
Chico said:
Sometimes, in example: it keep sending values 38 39 38 39 38 39....... Congratulation, if this is your biggest noise!! Chico, what you observe is LSB-noise, which cannot be avoided at all in digital systems! Assume, your input voltage is exactly at the edge between "38" and "39", then the least amount of noise will make the ADC reading toggle. You cannot stop this. It's like the reading of a DVM (digital voltmeter), sometimes you can see the last digit flickering even if the input signal is absolutely clean. The best way to remove this "noise" is the use of a moving average filter: Don't convert every single ADC reading into a MIDI signal, but first take 8, 16 or even more ADC readings in a row, calculate the average (some addings and a shifting) and convert this value to a MIDI signal. The averaging methode also helps to avoid too fast changes of MIDI signals, which make physically no sense. This deadzone methode, on the other hand, shows the disadvantage that you loose resolution if you make the deadzone too broad. Kai |
