I2C slave and scanning (#108)

* added examples

* i2c slave and scanning

* Create README.md

Author: maxint-rd

libraries/Wire/examples/i2cMinimalSlave/i2cMinimalSlave.ino

@@ -0,0 +1,57 @@
+/*
+  I2C Minimal Slave - CH32 I2C Slave example
+
+  Show the minimal code required to implement an I2C slave device with these features:
+     - handle I2C scanning (i.e. acknowledge data-less transaction)
+     - handle receiving data
+     - return data requested by master
+     - blink LED on PA2 according transfered value
+  
+  Compiled for CH32V003J4M6 (SOP8) using Arduino IDE v2.3.2, CH32 core v1.0.4. 
+  Optimize: Smallest (-Os default), Debug symbols: none, no UART: //#define UART_MODULE_ENABLED
+  Note - enable I2C slave functionality in /libraries/Wire/src/utility/twi.h
+    #define OPT_I2C_SLAVE 1
+
+  Using those options this sketch uses 9424 bytes (57%) of program storage space. Maximum is 16384 bytes.
+  Global variables use 580 bytes (28%) of dynamic memory, leaving 1468 bytes for local variables. Maximum is 2048 bytes.
+*/
+
+#include <Wire.h>
+#define MY_I2C_ADDRESS 0x33
+ 
+#undef LED_BUILTIN
+#define LED_BUILTIN PA2
+uint32_t _nBlinkSpeed=500;
+
+void ReceiveEvent(int nNumBytes) {
+  // receive value is stored to set the speed of blinking
+  _nBlinkSpeed=0;
+  while(nNumBytes>0)
+  {
+    _nBlinkSpeed<<=8;
+    _nBlinkSpeed|=Wire.read();
+    nNumBytes--;
+  }
+}
+
+void RequestEvent() {
+  // returned 32-bit value is the current speed of blinking
+  Wire.write((const uint8_t *)&_nBlinkSpeed, sizeof(_nBlinkSpeed));;
+}
+
+void setup() {
+  pinMode(LED_BUILTIN, OUTPUT);  // Initialize digital pin LED_BUILTIN as an output.
+  Wire.begin(MY_I2C_ADDRESS);
+  // Note: enable I2C slave functionality in /libraries/Wire/src/utility/twi.h to prevent error message for next two lines
+  Wire.onReceive(ReceiveEvent);
+  Wire.onRequest(RequestEvent);
+}
+
+void loop() {
+  static uint32_t uStart=millis();
+  if(millis()-uStart > _nBlinkSpeed)
+  { // blink the LED by reversing its state
+    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
+    uStart=millis();
+  }
+}

libraries/Wire/examples/i2c_scanner/README.md

@@ -0,0 +1,12 @@
+# I2C Scanner
+Original I2C Scanner example by Nick Gammon
+I2C Scanner - Written by Nick Gammon - Date: 20th April 2011 [source](http://arduino-info.wikispaces.com/LCD-Blue-I2C).
+
+Demonstrates CH32 Support for I2C scanning using Wire.endTransmission() without sending data. 
+To enable scanning these changes are required in libraries/Wire/src/utility/twi.c : 
+- timeout on an addresses should release the bus
+- allow only sending the address (without actual data)
+- smaller timeout: I2C_TIMEOUT_TICK 25 (was 100ms)
+
+Note: Currently there's no support for [Wire.setWireTimeout(timeout, reset_on_timeout)](https://www.arduino.cc/reference/en/language/functions/communication/wire/setwiretimeout/).
+Inspiration from [i2c_scanner](https://github.com/mockthebear/easy-ch32v003/tree/main/examples/i2c_scanner) by @mockthebear.

libraries/Wire/examples/i2c_scanner/i2c_scanner.ino

@@ -0,0 +1,60 @@
+
+// I2C Scanner
+// Written by Nick Gammon
+// Date: 20th April 2011
+
+// source: http://arduino-info.wikispaces.com/LCD-Blue-I2C
+
+// MMOLE: CH32 Support I2C scanning using Wire.endTransmission() without sending data
+// CH32 changes required in libraries/Wire/src/utility/twi.c
+//  - timeout on an addresses should release the bus
+//  - allow only sending the address (without actual data)
+//  - smaller timeout: I2C_TIMEOUT_TICK 25 (was 100ms)
+// Note: Currently there's no support for Wire.setWireTimeout(timeout, reset_on_timeout)
+// https://www.arduino.cc/reference/en/language/functions/communication/wire/setwiretimeout/
+// Inspiration from https://github.com/mockthebear/easy-ch32v003/tree/main/examples/i2c_scanner
+
+
+
+#include <Wire.h>
+
+void setup() {
+  Serial.begin (115200);
+
+  // Leonardo: wait for serial port to connect
+  while (!Serial) 
+    {
+    }
+
+  Serial.println ();
+  Serial.println ("I2C scanner. Scanning ...");
+  
+  Wire.begin();
+  while(true)
+  {
+
+  byte count = 0;
+  for (byte i = 8; i < 120; i++)
+  {
+    Wire.beginTransmission (i);
+    if (Wire.endTransmission () == 0)
+      {
+      Serial.print ("Found address: ");
+      Serial.print (i, DEC);
+      Serial.print (" (0x");
+      Serial.print (i, HEX);
+      Serial.println (")");
+      count++;
+      delay (1);  // maybe unneeded?
+      } // end of good response
+  } // end of for loop
+  Serial.println ("Done.");
+  Serial.print ("Found ");
+  Serial.print (count, DEC);
+  Serial.println (" device(s).");
+  delay(1000);
+  Serial.println ("Scanning again...");
+  }
+}  // end of setup
+
+void loop() {}

libraries/Wire/src/Wire.cpp

@@ -93,10 +93,13 @@ void TwoWire::begin(uint8_t address, bool generalCall, bool NoStretchMode)
 
   if (_i2c.isMaster == 0) 
   {
+#if OPT_I2C_SLAVE
+	// MMOLE: these four lines were all commented
     // i2c_attachSlaveTxEvent(&_i2c, reinterpret_cast<void(*)(i2c_t*)>(&TwoWire::onRequestService));
     // i2c_attachSlaveRxEvent(&_i2c, reinterpret_cast<void(*)(i2c_t*, uint8_t*, int)>(&TwoWire::onReceiveService));
-    // i2c_attachSlaveTxEvent(&_i2c, onRequestService);
-    // i2c_attachSlaveRxEvent(&_i2c, onReceiveService); 
+    i2c_attachSlaveTxEvent(&_i2c, onRequestService);
+    i2c_attachSlaveRxEvent(&_i2c, onReceiveService); 
+#endif
   }
 }
 
@@ -277,11 +280,13 @@ size_t TwoWire::write(uint8_t data)
       txDataSize++;
     }
   } else {
+#if OPT_I2C_SLAVE
     // in slave send mode
     // reply to master
     if (i2c_slave_write(&_i2c, &data, 1) != I2C_OK) {
       ret = 0;
     }
+#endif // #if OPT_I2C_SLAVE
   }
   return ret;
 }
@@ -309,11 +314,13 @@ size_t TwoWire::write(const uint8_t *data, size_t quantity)
       txDataSize += quantity;
     }
   } else {
+#if OPT_I2C_SLAVE
     // in slave send mode
     // reply to master
     if (i2c_slave_write(&_i2c, (uint8_t *)data, quantity) != I2C_OK) {
       ret = 0;
     }
+  #endif // #if OPT_I2C_SLAVE
   }
   return ret;
 }
@@ -372,6 +379,7 @@ void TwoWire::flush(void)
 
 
 // behind the scenes function that is called when data is received
+#if OPT_I2C_SLAVE
 void TwoWire::onReceiveService(i2c_t *obj)
 {
   uint8_t *inBytes = (uint8_t *) obj->i2cTxRxBuffer;
@@ -413,7 +421,9 @@ void TwoWire::onRequestService(i2c_t *obj)
     TW->user_onRequest();
   }
 }
+#endif // #if OPT_I2C_SLAVE
 
+#if OPT_I2C_SLAVE
 // sets function called on slave write
 void TwoWire::onReceive(cb_function_receive_t function)
 {
@@ -425,6 +435,7 @@ void TwoWire::onRequest(cb_function_request_t function)
 {
   user_onRequest = function;
 }
+#endif // #if OPT_I2C_SLAVE