Additional information and document update here on my site: pcf8575 Article.
Library to use i2c analog IC with arduino and esp8266. Can read and write digital value with only 2 wire (perfect for ESP-01).
Tutorial:
To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder PCF8575. Check that the PCF8575 folder contains PCF8575\\.cpp
and PCF8575.h
. Place the DHT library folder your <arduinosketchfolder>/libraries/
folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.
I try to simplify the use of this IC, with a minimal set of operation.
PCF8575 address map 0x20 default
Constructor: you must pas the address of i2c (to check the adress use this guide I2cScanner)
PCF8575(uint8_t address);
for esp8266 if you want specify SDA e SCL pin use this:
PCF8575(uint8_t address, uint8_t sda, uint8_t scl);
You must set input/output mode:
pcf8575.pinMode(P0, OUTPUT);
pcf8575.pinMode(P1, INPUT);
pcf8575.pinMode(P2, INPUT);
then IC as you can see in the image have 8 digital input/output:
So to read all analog input in one trasmission you can do (even if I use a 10millis debounce time to prevent too much read from i2c):
PCF8575::DigitalInput di = PCF8575.digitalReadAll();
Serial.print(di.p0);
Serial.print(" - ");
Serial.print(di.p1);
Serial.print(" - ");
Serial.print(di.p2);
Serial.print(" - ");
Serial.println(di.p3);
To follow a request (you can see It on issue #5) I create a define variable to work with low memori device, if you decomment this line on .h file of the library:
// #define PCF8575_LOW_MEMORY
Enable low memory props and gain about 7byte of memory, and you must use the method to read all like so:
byte di = pcf8575.digitalReadAll();
Serial.print("READ VALUE FROM PCF: ");
Serial.println(di, BIN);
where di is a byte like 11100011110001, so you must do a bitwise operation to get the data, operation that I already do in the "normal" mode, here an example:
p0 = ((di & bit(0))>0)?HIGH:LOW;
p1 = ((di & bit(1))>0)?HIGH:LOW;
p2 = ((di & bit(2))>0)?HIGH:LOW;
p3 = ((di & bit(3))>0)?HIGH:LOW;
p4 = ((di & bit(4))>0)?HIGH:LOW;
p5 = ((di & bit(5))>0)?HIGH:LOW;
p6 = ((di & bit(6))>0)?HIGH:LOW;
p7 = ((di & bit(7))>0)?HIGH:LOW;
if you want read a single input:
int p1Digital = PCF8575.digitalRead(P1); // read P1
If you want write a digital value you must do:
PCF8575.digitalWrite(P1, HIGH);
or:
PCF8575.digitalWrite(P1, LOW);
You can also use interrupt pin: You must initialize the pin and the function to call when interrupt raised from PCF8575
// Function interrupt
void keyPressedOnPCF8575();
// Set i2c address
PCF8575 pcf8575(0x39, ARDUINO_UNO_INTERRUPT_PIN, keyPressedOnPCF8575);
Remember you can't use Serial or Wire on interrupt function.
The better way is to set only a variable to read on loop:
void keyPressedOnPCF8575(){
// Interrupt called (No Serial no read no wire in this function, and DEBUG disabled on PCF library)
keyPressed = true;
}