Adjustable sampling speed on our arduino oscilloscope (exceloscope part 6) & what is INPUT_PULLUP

Updates to the Arduino Oscilloscope code from prior videos to allow adjustment of sampling speed by plugging a jumper wire to one of the digital input pins.
Also a detailed explanation of the INPUT_PULLUP mode for Arduino digital input pins.
00:00 Introduction
00:53 Code changes
01:08 configure digital input pins
01:20 INPUT_PULLUP mode explanation
02:30 Adjustable Prescaler code
03:05 Sampling code standard and with delay for low frequencies
03:40 Main loop
04:00 Output stage code (handling integer overflow /rollover issues)
05:00 Frequency Range String
05:30 Demonstration in action
06:40 Excel speadsheet updates to display sampling rate frequency range