mirror of
https://github.com/xreef/PCF8574_library.git
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128 lines
4.4 KiB
Markdown
128 lines
4.4 KiB
Markdown
<div>
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<a href="https://www.mischianti.org/forums/forum/mischiantis-libraries/pcf8574-i2c-digital-i-o-expander/"><img
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src="https://github.com/xreef/LoRa_E32_Series_Library/raw/master/resources/buttonSupportForumEnglish.png" alt="Support forum pcf8574 English"
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align="right"></a>
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</div>
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<div>
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<a href="https://www.mischianti.org/it/forums/forum/le-librerie-di-mischianti/pcf8574-expander-digitale-i-o-i2c/"><img
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src="https://github.com/xreef/LoRa_E32_Series_Library/raw/master/resources/buttonSupportForumItaliano.png" alt="Forum supporto pcf8574 italiano"
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align="right"></a>
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</div>
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### Additional information and document update here on my site: [pcf8574 Article](https://www.mischianti.org/2019/01/02/pcf8574-i2c-digital-i-o-expander-fast-easy-usage/).
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### If you need more pins [here](https://www.mischianti.org/2019/07/22/pcf8575-i2c-16-bit-digital-i-o-expander/) you can find pcf8575 16bit version of the IC.
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### Version 2.2
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Library to use i2c analog IC with arduino and esp8266. Can read and write digital value with only 2 wire (perfect for ESP-01).
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Tutorial:
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To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder PCF8574. Check that the PCF8574 folder contains `PCF8574\\.cpp` and `PCF8574.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.
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# Reef complete PCF8574 PCF8574AP digital input and output expander with i2c bus.
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I try to simplify the use of this IC, with a minimal set of operation.
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PCF8574P address map 0x20-0x27
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PCF8574AP address map 0x38-0x3f
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Constructor:
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you must pas the address of i2c (to check the adress use this guide [I2cScanner](https://playground.arduino.cc/Main/I2cScanner))
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```cpp
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PCF8574(uint8_t address);
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```
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for esp8266 if you want specify SDA e SCL pin use this:
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```cpp
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PCF8574(uint8_t address, uint8_t sda, uint8_t scl);
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```
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You must set input/output mode:
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```cpp
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pcf8574.pinMode(P0, OUTPUT);
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pcf8574.pinMode(P1, INPUT);
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pcf8574.pinMode(P2, INPUT);
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```
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then IC as you can see in the image have 8 digital input/output:
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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):
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```cpp
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PCF8574::DigitalInput di = PCF8574.digitalReadAll();
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Serial.print(di.p0);
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Serial.print(" - ");
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Serial.print(di.p1);
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Serial.print(" - ");
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Serial.print(di.p2);
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Serial.print(" - ");
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Serial.println(di.p3);
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```
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To follow a request (you can see It on [issue #5](https://github.com/xreef/PCF8574_library/issues/5)) I create a define variable to work with low memori device, if you decomment this line on .h file of the library:
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```cpp
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// #define PCF8574_LOW_MEMORY
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```
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Enable low memory props and gain about 7byte of memory, and you must use the method to read all like so:
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```cpp
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byte di = pcf8574.digitalReadAll();
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Serial.print("READ VALUE FROM PCF: ");
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Serial.println(di, BIN);
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```
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where di is a byte like 1110001, so you must do a bitwise operation to get the data, operation that I already do in the "normal" mode, here an example:
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```cpp
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p0 = ((di & bit(0))>0)?HIGH:LOW;
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p1 = ((di & bit(1))>0)?HIGH:LOW;
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p2 = ((di & bit(2))>0)?HIGH:LOW;
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p3 = ((di & bit(3))>0)?HIGH:LOW;
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p4 = ((di & bit(4))>0)?HIGH:LOW;
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p5 = ((di & bit(5))>0)?HIGH:LOW;
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p6 = ((di & bit(6))>0)?HIGH:LOW;
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p7 = ((di & bit(7))>0)?HIGH:LOW;
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```
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if you want read a single input:
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```cpp
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int p1Digital = PCF8574.digitalRead(P1); // read P1
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```
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If you want write a digital value you must do:
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```cpp
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PCF8574.digitalWrite(P1, HIGH);
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```
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or:
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```cpp
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PCF8574.digitalWrite(P1, LOW);
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```
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You can also use interrupt pin:
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You must initialize the pin and the function to call when interrupt raised from PCF8574
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```cpp
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// Function interrupt
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void keyPressedOnPCF8574();
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// Set i2c address
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PCF8574 pcf8574(0x39, ARDUINO_UNO_INTERRUPT_PIN, keyPressedOnPCF8574);
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```
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Remember you can't use Serial or Wire on interrupt function.
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The better way is to set only a variable to read on loop:
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```cpp
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void keyPressedOnPCF8574(){
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// Interrupt called (No Serial no read no wire in this function, and DEBUG disabled on PCF library)
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keyPressed = true;
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}
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```
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For the examples I use this wire schema on breadboard:
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