xreef/PCF8574_library

The digitalRead() does not work

kotakomputer opened this issue · 3 comments

kotakomputer commented

I try digitalRead(P1) but does not work, result always LOW.
Using digitalReadAll(); the P1 result is HIGH (this is correct because I put 5V to P1).

kotakomputer commented

SOLVED. Must using digitalRead(P1, true).

xreef commented

Hi kotakomputer,
I think that It's usefully to undestand the problem.
How do you initialize the pin, like so
pcf8574.pinMode(P1, INPUT_PULLUP)
?

true in digital read bypass the debounce function that try to find a state change, so if you define P1 as INPUT_PULLUP and put HIGH the pin the state change not finded, but if you put only INPUT I think there is a problem in the library.

Please give me a feedback.
Thanks Renzo

alirezaimi commented

I have this problem, and using true parameter in digitalRead method not work for me ,
result is always LOW .

pcf8574.pinMode(P1, OUTPUT, LOW);
pcf8574.pinMode(P2, OUTPUT, HIGH);

pcf8574.digitalWrite(P1, HIGH);
pcf8574.digitalWrite(P2, HIGH);
int relay_1_state = pcf8574.digitalRead(P1, true); // LOW
int relay_2_state = pcf8574.digitalRead(P2, true); // LOW

or

pcf8574.digitalWrite(P1, HIGH);
pcf8574.digitalWrite(P2, HIGH);
int relay_1_state = pcf8574.digitalRead(P1); // LOW
int relay_2_state = pcf8574.digitalRead(P2); // LOW