ARDUINO UNOThe digital pin port is unstable after power on.
in use4*4When the matrix keyboard is encountered, the input level can not be stable and has been recognized as high level.
After discovering this problem, first check whether the program is wrong. After checking, there was no problem with the program.
So check the voltage value of the port during the period, this is a more intuitive method, you can clearly know the level of the output port. The result is that the voltage figure is only a few points below zero when the button is not pressed, which obviously belongs to low level. When pressed, the voltage is high. But no matter how high or low level it is,The program is highly programmed.
After the above two steps, we have not detected any problems.
Later, through enquiries and enquiries. not have understood until thenThe pin acts as a digital input, but does not connect any pull resistance, is in suspension state, is susceptible to electronic noise interference and changes its level state randomly.
Reference resourcesMCUData Handbook >A103J5V” causes the whole row of pins to be pulled up, and the operation is exactly the same as before the resistance. At first, I was rather muddled. I don’t know why.
>, it can run normally.
