Added README, example and cache feature

Centipede.cpp

@@ -10,6 +10,9 @@
 #include <Wire.h>
 
 uint8_t CSDataArray[2] = {0};
+#ifdef CS_CACHE
+uint8_t CSDataCacheArray[16] = {0};
+#endif
 
 #define CSAddress 0b0100000
 
@@ -41,6 +44,13 @@ void Centipede::initialize()
 }
 
 
+#ifdef CS_CACHE
+void Centipede::StoreCache(int port) {
+    CSDataCacheArray[port] = CSDataArray[0];
+    CSDataCacheArray[port+1] = CSDataArray[1];
+}
+#endif
+
 void Centipede::WriteRegisters(int port, int startregister, int quantity) {
 
   Wire.beginTransmission(CSAddress + port);
@@ -131,14 +141,24 @@ void Centipede::digitalWrite(int pin, int level) {
 
 }
 
-int Centipede::digitalRead(int pin) {
+// While the cache parameter is always taken in input, it will be effective only once CS_CACHE is defined in Centipede.h file
+int Centipede::digitalRead(int pin, int cache) {
 
   int port = pin >> 4;
   int subregister = (pin & 8) >> 3;
 
+#ifdef CS_CACHE
+  if ( !cache ) {
+    ReadRegisters(port, 0x12 + subregister, 1);
+    StoreCache(port);
+  }
+
+  int returnval = (CSDataCacheArray[port] >> (pin - ((port << 1) + subregister)*8)) & 1;
+#else
   ReadRegisters(port, 0x12 + subregister, 1);
 
   int returnval = (CSDataArray[0] >> (pin - ((port << 1) + subregister)*8)) & 1;
+#endif
 
   return returnval;
 
@@ -217,6 +237,10 @@ int Centipede::portRead(int port) {
 
   ReadRegisters(port, 0x12, 2);
 
+#ifdef CS_CACHE
+  StoreCache(port);
+#endif
+
   int receivedval = CSDataArray[0];
   receivedval |= CSDataArray[1] << 8;
 

Centipede.h

@@ -4,13 +4,18 @@
 #ifndef Centipede_h
 #define Centipede_h
 
+#define CS_CACHE
+
 #if defined(ARDUINO) && ARDUINO >= 100
 #include "Arduino.h"
 #else
 #include "WProgram.h"
 #endif
 
 extern uint8_t CSDataArray[2];
+#ifdef CS_CACHE
+extern uint8_t CSDataCacheArray[16];
+#endif
 
 class Centipede
 {
@@ -19,7 +24,7 @@ class Centipede
     void pinMode(int pin, int mode);
     void pinPullup(int pin, int mode);
     void digitalWrite(int pin, int level);
-    int digitalRead(int pin);
+    int digitalRead(int pin, int cache = false);
     void portMode(int port, int value);
     void portPullup(int port, int value);
     void portWrite(int port, int value);
@@ -33,6 +38,9 @@ class Centipede
     void WriteRegisters(int port, int startregister, int quantity);
     void ReadRegisters(int port, int startregister, int quantity);
     void WriteRegisterPin(int port, int regpin, int subregister, int level);
+#ifdef CS_CACHE
+    void StoreCache(int port);
+#endif
 };
 
 #endif

README.md

@@ -1 +1,28 @@
 # Centipede Shield Library
+
+## Reference
+
+The main documentation is reported in [macetech wiki](https://docs.macetech.com/doku.php/centipede_shield)
+
+Nevertheless this could be outdated (eg .getIntF is missing in the wiki currently).
+
+## Methods
+
+* .digitalWrite([0...127], [LOW...HIGH]) - Acts like normal digitalWrite
+* .digitalRead([0...127]) - Acts like normal digitalRead
+* .pinMode([0...127], [INPUT...OUTPUT]) - Acts like normal pinMode
+* .pinPullup([0...127], [LOW...HIGH]) - Activates internal 100K pullups on inputs when HIGH.
+* .portWrite([0...7], [0...65535]) - Writes 16-bit value to one port (chip). Useful for writing 16 outputs at the same time.
+* .portRead([0...7]) - Reads 16-bit value from one port (chip)
+* .portMode([0...7], [0...65535]) - Write I/O mask to one port (chip). In binary, a 0 means output and a 1 means input. Easier to use than a long list of pinMode() commands.
+* .portPullup([0...7], [0...65535]) - Sets pullups on one port (chip). In binary, a 0 means no pullup and a 1 means pullup is active.
+* .portInterrupts([0...7],[0...65535],[0...65535],[0...65535]) - Configure interrupts
+*                 [device number],[use interrupt on pin],[default value],[interrupt when != default]
+* .portCaptureRead(0...7) - Reads 16-bit value registers as they were when interrupt occurred
+* .getIntF(0..7) - These return an interrupt flag state that allows you to determine which port (device) produced an interrupt (and it could be more than one device).
+* .init() - Sets all registers to initial values
+
+## Compile Options
+
+if `CS_CACHE` is defined, the library will use sightly more memory, but will allow `.digitalRead([0-127, [TRUE|FALSE])` where the latter parametet will define if to return the value cached or if has to be taken fresh from the port.
+If you read all the 127 input from i2c, this should br faster, at the price of 512 byte of memory.

examples/sample.ino

@@ -0,0 +1,63 @@
+// Example code for Centipede Library
+// Works with Centipede Shield or MCP23017 on Arduino I2C port
+
+#include <Wire.h>
+#include <Centipede.h>
+
+
+/* Available commands
+  .digitalWrite([0...127], [LOW...HIGH]) - Acts like normal digitalWrite
+  .digitalRead([0...127]) - Acts like normal digitalRead
+  .pinMode([0...127], [INPUT...OUTPUT]) - Acts like normal pinMode
+  .portWrite([0...7], [0...65535]) - Writes 16-bit value to one port (chip)
+  .portRead([0...7]) - Reads 16-bit value from one port (chip)
+  .portMode([0...7], [0...65535]) - Write I/O mask to one port (chip)
+  .pinPullup([0...127], [LOW...HIGH]) - Sets pullup on input pin
+  .portPullup([0...7], [0...65535]) - Sets pullups on one port (chip)
+  .portInterrupts([0...7],[0...65535],[0...65535],[0...65535]) - Configure interrupts
+                  [device number],[use interrupt on pin],[default value],[interrupt when != default]
+  .portCaptureRead(0...7) - Reads 16-bit value registers as they were when interrupt occurred
+  .init() - Sets all registers to initial values
+
+  Examples
+  CS.init();
+  CS.pinMode(0,OUTPUT);
+  CS.digitalWrite(0, HIGH);
+  int recpin = CS.digitalRead(0);
+  CS.portMode(0, 0b0111111001111110); // 0 = output, 1 = input
+  CS.portWrite(0, 0b1000000110000001); // 0 = LOW, 1 = HIGH
+  int recport = CS.portRead(0);
+  CS.pinPullup(1,HIGH);
+  CS.portPullup(0, 0b0111111001111110); // 0 = no pullup, 1 = pullup
+  CS.portInterrupts(0,0b0000000000000001,0b0000000000000000,0b0000000000000001);
+*/
+
+Centipede CS; // create Centipede object
+
+
+void setup()
+{
+  Wire.begin(); // start I2C
+
+  CS.initialize(); // set all registers to default
+
+  CS.portMode(0, 0b0000000000000000); // set all pins on chip 0 to output (0 to 15)
+  //CS.portMode(1, 0b0000000000000000); // set all pins on chip 1 to output (16 to 31)
+
+  //TWBR = 12; // uncomment for 400KHz I2C (on 16MHz Arduinos)
+
+}
+
+
+void loop()
+{  
+  for (int i = 0; i < 16; i++) {
+    CS.digitalWrite(i, HIGH);
+    delay(10);
+  }
+
+  for (int i = 0; i < 16; i++) {
+    CS.digitalWrite(i, LOW);
+    delay(10);
+  } 
+}