add rotaryEncoder example

Author: RobTillaart

libraries/PCF8574/examples/PCF8574_rotaryEncoder/PCF8574_rotaryEncoder.ino

@@ -0,0 +1,131 @@
+//
+// FILE: PCF8574_rotaryEncoder.ino
+// AUTHOR: Rob Tillaart
+// DATE: 2021-05-08
+//
+// PUPROSE: demo PCF8574 as rotary encoder reader.
+
+//
+// RotaryEncoder PCF8574 UNO
+// --------------------------------------
+// pin A pin 0 (add pull ups, also for not connected lines)
+// pin B pin 1
+// .... .... (up to 4 RE)
+//
+// SDA A4
+// SCL A5
+// INT 2
+//
+// note: a dedicated rotary decoder class is created 
+// - https://github.com/RobTillaart/rotaryDecoder -
+
+
+#include "PCF8574.h"
+
+PCF8574 decoder(0x20);
+
+
+// hold position of 4 RE + last position
+uint8_t lastpos[4] = {0, 0, 0, 0};
+int32_t encoder[4] = {0, 0, 0, 0};
+volatile bool flag = false;
+
+void moved()
+{
+ flag = true;
+}
+
+
+void setup()
+{
+ Serial.begin(115200);
+ Serial.println(__FILE__);
+ Serial.print("PCF8574_LIB_VERSION:\t");
+ Serial.println(PCF8574_LIB_VERSION);
+
+ pinMode(2, INPUT_PULLUP);
+ attachInterrupt(0, moved, FALLING);
+ flag = false;
+
+ Wire.begin();
+ if (decoder.begin() == false)
+ {
+ Serial.println("\nERROR: cannot communicate to keypad.\nPlease reboot / adjust address.\n");
+ while (1);
+ }
+ Wire.setClock(600000);
+ 
+ initRotaryDecoder();
+
+ uint32_t start = micros();
+ for (int i = 0; i < 10; i++)
+ {
+ updateRotaryDecoder();
+ }
+ uint32_t stop = micros();
+ Serial.println((stop - start) * 0.1);
+}
+
+
+void loop()
+{
+ if (flag)
+ {
+ updateRotaryDecoder();
+ flag = false;
+ for (int i = 0; i < 4; i++)
+ {
+ Serial.print("\t");
+ Serial.print(encoder[i]);
+ }
+ Serial.println();
+ }
+}
+
+
+void initRotaryDecoder()
+{
+ uint8_t val = decoder.read8();
+ for (uint8_t i = 0; i < 4; i++)
+ {
+ lastpos[i] = val & 0x03;
+ val >>= 2;
+ }
+}
+
+
+// assumes 4 rotary encoders connected to one PCF8574
+void updateRotaryDecoder()
+{
+ uint8_t val = decoder.read8();
+
+ // check which of 4 has changed
+ for (uint8_t i = 0; i < 4; i++)
+ {
+ uint8_t currentpos = (val & 0x03);
+ if (lastpos[i] != currentpos) // moved!
+ {
+ uint8_t change = (lastpos[i] << 2) | currentpos;
+ switch (change)
+ {
+ case 0b0001: // fall through..
+ case 0b0111:
+ case 0b1110:
+ case 0b1000:
+ encoder[i]++;
+ break;
+ case 0b0010:
+ case 0b0100:
+ case 0b1101:
+ case 0b1011:
+ encoder[i]--;
+ break;
+ }
+ lastpos[i] = currentpos;
+ val >>= 2;
+ }
+ }
+}
+
+
+// -- END OF FILE --