Wire: implement STOP sequence to recover I2C bus.

Usefull in case of bus stuck after a reset for example
Fixes stm32duino#1661

Signed-off-by: Alexandre Bourdiol <[email protected]>

Author: ABOSTM

libraries/Wire/src/Wire.cpp

@@ -83,6 +83,8 @@ void TwoWire::begin(uint8_t address, bool generalCall)
 
   _i2c.generalCall = (generalCall == true) ? 1 : 0;
 
+  recoverBus(); // in case I2C bus (device) is stuck after a reset for example
+
   i2c_custom_init(&_i2c, 100000, I2C_ADDRESSINGMODE_7BIT, ownAddress);
 
   if (_i2c.isMaster == 0) {
@@ -501,6 +503,27 @@ inline void TwoWire::resetTxBuffer(void)
   }
 }
 
+// Send STOP sequence to recover bus.
+// Usefull in case of bus stuck after a reset for example
+void TwoWire::recoverBus(void)
+{
+  pinMode(pinNametoDigitalPin(_i2c.sda), OUTPUT);
+  pinMode(pinNametoDigitalPin(_i2c.scl), OUTPUT);
+
+  for (int i = 0; i < 10; i++) {
+    digitalWrite(pinNametoDigitalPin(_i2c.sda), LOW);
+    delay(3);
+    digitalWrite(pinNametoDigitalPin(_i2c.scl), HIGH);
+    delay(3);
+    digitalWrite(pinNametoDigitalPin(_i2c.sda), HIGH);
+    delay(3);
+    digitalWrite(pinNametoDigitalPin(_i2c.scl), LOW);
+    delay(3);
+  }
+  pinMode(pinNametoDigitalPin(_i2c.sda), INPUT);
+  pinMode(pinNametoDigitalPin(_i2c.scl), INPUT);
+}
+
 // Preinstantiate Objects //////////////////////////////////////////////////////
 
 TwoWire Wire = TwoWire(); //D14-D15

libraries/Wire/src/Wire.h

@@ -66,6 +66,7 @@ class TwoWire : public Stream {
 
     void resetRxBuffer(void);
     void resetTxBuffer(void);
+    void recoverBus(void);
 
   public:
     TwoWire();