Since the line length does not change, this delay is always the same and included in the resulting time (until the signal arrives). No debounce is used for the contacts, therefore it is necessary to use a reduced external pullup resistor for longer contact to the contacts.ĭepending on the length of the cable used to the switches, a delay must also be taken into account. This change is registered in the program immediately, the order of each input is tested several times per millisecond. By switching the button, the value 0V (GND) is applied to the given terminal. The switching contacts used in this stopwatch connection use an internal PULLUP resistor of 50kohm Arduino, by which these digital inputs are connected in parallel to a 5V power supply. Since the stopwatch is mainly used to calculate attack time, which lasts up to about one minute, these differences are negligible and accuracy is sufficient for indicative measurements. However, since the differences in the frequency of the crystals are very small, the deviation will only become apparent when compared over a longer period of time. For this reason, the timing is also more accurate. The original Arduino boards have a more accurate 16MHz crystal than the Chinese. The accuracy of the stopwatch depends on the crystal (oscillator) used. The result is a stopwatch that allows you to measure and display time in hundreds of seconds. When the stopwatch is running in such a configuration, the stopwatch would be misaligned by 3 hundred per display display.įor this reason, it was necessary to change the logic of the display (update only a specific position on the display when changing it, not the entire line), increase the speed of the I2C bus (from the original 400 kHz). The problem with implementing hundreds of hundreds was that the system logic is executed every 10 milliseconds. Thus, once every 100 milliseconds, one tenth is added (if the time is active) and the display is updated (both times are displayed). The decimal stopwatch logic is executed every 100 milliseconds.
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