Zeroplus Arduino starter kit with Logic Analyzer Manual page 41

REMARKS
1. As a rule of thum b, sam ple a digital signal at a frequency at least 4
tim es the signal's frequency. When the frequency of the target signal
is unknow n, choose a sam ple rate so that there are a minim um of four
sam ples points per cycle (2 when High, 2 when Low). You can display
the number of sam ples on the waveform in the menu option m> customize
waveform area m> waveform information. How often you record (sam ple)
the voltage value on each channel is called the sam ple speed. A higher
sam ple speed ensures that you are not missing anything. Too high and
you'll fill the memory with unnecessary sam ples. Too low and you'll miss
a lot of information, resulting in a waveform w hich is not a correct
representation of the real signal.
2. How to determine whether a certain voltage should be read as a 0 or a
1? By comparing it to a reference value, also called the trigger level.
Anything below that value is a 0. Anything above it is a 1.
3. Adjust the trigger position to capture more data before (pre-trigger)
or after (post-trigger) the trigger event.
4. It happens because the channels are not updated at the same tim e.
Look at the code, you can see that in the first counter function it is
w ritten PORTB = bus_counter whereas the other counter updates each pin
with digitalWrite(). digitalWrite() updates the pins one after another .
PORTB updates all pins at once.
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