mirror of
https://github.com/xreef/PCF8574_library.git
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140 lines
4.6 KiB
Markdown
140 lines
4.6 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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#
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#
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#
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#
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#
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#
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### Additional information and documentation 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 the 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 wires (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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## Changelog
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06/04/2022: v2.3.0 Fix package size
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30/12/2021: v2.2.4 Minor fix and remove deprecated declaration
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23/11/2020: v2.2.2 Add multiple implementation for encoder management (you can enable by uncomment relative define)
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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 operations.
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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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Pass the address of I2C (to check the address 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 to specify SDA and SCL pins 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 has 8 digital input/output ports:
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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 memory devices, if you uncomment this line in the .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 7 bytes 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. For 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 to 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 to write a digital value:
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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 an 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 an interrupt function.
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It's better to only set 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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