uint8_t SoftwareWire::i2c_readbit(void)
{
i2c_sda_hi(); // 'hi' is the same as releasing the line
i2c_scl_hi();
// Check if clock stretching by the Slave should be detected.
if( _stretch)
{
// Wait until the clock is high, the Slave could keep it low for clock stretching.
unsigned long prevMillis = millis();
while( i2c_scl_read() == 0)
{
if( millis() - prevMillis >= _timeout)
break;
};
}
// After the clock stretching, this delay has still be done before reading sda.
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
uint8_t c = i2c_sda_read();
i2c_scl_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
return(c);
}
//
// Send a START Condition
//
// The SDA and SCL should already be high.
//
// The SDA and SCL will both be low after this function.
// When writing the address, the Master makes them high.
//
// Return value:
// true : software i2c bus is okay.
// false : failed, some kind of hardware bus error.
//
boolean SoftwareWire::i2c_start(void)
{
i2c_sda_hi(); // can perhaps be removed some day ? if the rest of the code is okay
i2c_scl_hi(); // can perhaps be removed some day ? if the rest of the code is okay
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
// Both the sda and scl should be high.
// If not, there might be a hardware problem with the i2c bus signal lines.
// This check was added to prevent that a shortcut of sda would be seen as a valid ACK
// from a i2c Slave.
uint8_t sda_status = i2c_sda_read();
uint8_t scl_status = i2c_scl_read();
if(sda_status == 0 || scl_status == 0)
{
return(false);
}
else
{
i2c_sda_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_scl_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
}
return(true);
}
// Perform one step of the I2C FSM
static void i2c_step(void)
{
switch(g_i2c_state)
{
// Idle states
case I2C_IDLE: // Idle bus with SCL and SDA high
break;
case I2C_READY: // Bus ready for activity with SCL and SDA low
break;
// Start states
case I2C_START:
i2c_init(); // Sets SDA and SCL to 1
g_i2c_state = I2C_START_2;
break;
case I2C_START_2:
i2c_sda(0); // SDA falling while SCL 1 => Start bit
g_i2c_state = I2C_START_3;
break;
case I2C_START_3:
i2c_scl(0); // Now SDA and SCL are both 0, ready for bus activity
g_i2c_state = I2C_READY;
break;
// Write states
case I2C_WRITE:
i2c_sda(g_i2c_to_write & (1 << g_i2c_bit)); // SDA reflects data bit
g_i2c_state = I2C_WRITE_2;
break;
case I2C_WRITE_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_WRITE_3;
break;
case I2C_WRITE_3:
i2c_scl(0); // Toggle SCL low
if(g_i2c_bit == 0)
g_i2c_state = I2C_WRITE_ACK_1;
else
{
g_i2c_bit--;
g_i2c_state = I2C_WRITE;
}
break;
case I2C_WRITE_ACK_1:
i2c_sda(1); // Release SDA to allow the slave to ACK or NACK
g_i2c_state = I2C_WRITE_ACK_2;
break;
case I2C_WRITE_ACK_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_WRITE_ACK_3;
break;
case I2C_WRITE_ACK_3:
if(i2c_sda_read()) // Read the acknowledgement bit
g_i2c_state = I2C_WRITE_GOT_NACK;
else
g_i2c_state = I2C_WRITE_GOT_ACK;
i2c_scl(0); // Toggle SCL low
break;
case I2C_WRITE_GOT_ACK:
break;
case I2C_WRITE_GOT_NACK:
break;
// Read states
case I2C_READ:
i2c_sda(1); // Release SDA to allow the slave to transmit data
g_i2c_state = I2C_READ_2;
break;
case I2C_READ_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_READ_3;
break;
case I2C_READ_3:
if(i2c_sda_read())
g_i2c_read |= (1 << g_i2c_bit);
i2c_scl(0); // Toggle SCL low
if(g_i2c_bit == 0)
g_i2c_state = I2C_READ_4;
else
{
g_i2c_bit--;
g_i2c_state = I2C_READ_2;
}
break;
case I2C_READ_4:
i2c_sda(0); // Reassert control over SDA again and pull it low for an ACK
g_i2c_state = I2C_READ_ACK_1;
break;
case I2C_READ_ACK_1:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_READ_ACK_2;
break;
case I2C_READ_ACK_2:
i2c_scl(0); // Toggle SCL low
g_i2c_state = I2C_READ_ENDED;
break;
case I2C_READ_ENDED:
break;
// Stop states
case I2C_STOP:
i2c_sda(0);
g_i2c_state = I2C_STOP_2;
break;
case I2C_STOP_2:
i2c_scl(1);
g_i2c_state = I2C_STOP_3;
break;
case I2C_STOP_3:
i2c_sda(1);
g_i2c_state = I2C_IDLE;
break;
// Default state
default:
break;
}
}
//
// printStatus
// -----------
// Print information to the Serial port
// Used during developing and debugging.
// Call it with the Serial port as parameter:
// myWire.printStatus(Serial);
// This function is not compatible with the Wire library.
// When this function is not called, it does not use any memory.
//
void SoftwareWire::printStatus( HardwareSerial& Ser)
{
Ser.println(F("-------------------"));
Ser.println(F("SoftwareWire Status"));
Ser.println(F("-------------------"));
Ser.print(F(" F_CPU = "));
Ser.println(F_CPU);
Ser.print(F(" sizeof(SoftwareWire) = "));
Ser.println(sizeof(SoftwareWire));
Ser.print(F(" _transmission status = "));
Ser.println(_transmission);
Ser.print(F(" _i2cdelay = "));
Ser.print(_i2cdelay);
if( _i2cdelay == 0)
Ser.print(F(" (free running)"));
Ser.println();
Ser.print(F(" _pullups = "));
Ser.print(_pullups);
if( _pullups)
Ser.print(F(" (enabled)"));
Ser.println();
Ser.print(F(" _timeout = "));
Ser.print(_timeout);
Ser.println(F(" ms"));
Ser.print(F(" SOFTWAREWIRE_BUFSIZE = "));
Ser.println(SOFTWAREWIRE_BUFSIZE);
Ser.print(F(" rxBufPut = "));
Ser.println(rxBufPut);
Ser.print(F(" rxBufGet = "));
Ser.println(rxBufGet);
Ser.print(F(" available() = "));
Ser.println(available());
Ser.print(F(" rxBuf (hex) = "));
for(int ii=0; ii<SOFTWAREWIRE_BUFSIZE; ii++)
{
if(rxBuf[ii] < 16)
Ser.print(F("0"));
Ser.print(rxBuf[ii],HEX);
Ser.print(F(" "));
}
Ser.println();
Ser.print(F(" _sdaPin = "));
Ser.println(_sdaPin);
Ser.print(F(" _sclPin = "));
Ser.println(_sclPin);
Ser.print(F(" _sdaBitMast = 0x"));
Ser.println(_sdaBitMask, HEX);
Ser.print(F(" _sclBitMast = 0x"));
Ser.println(_sclBitMask, HEX);
Ser.print(F(" _sdaPortReg = "));
Ser.println( (uint16_t) _sdaPortReg, HEX);
Ser.print(F(" _sclPortReg = "));
Ser.println( (uint16_t) _sclPortReg, HEX);
Ser.print(F(" _sdaDirReg = "));
Ser.println( (uint16_t) _sdaDirReg, HEX);
Ser.print(F(" _sclDirReg = "));
Ser.println( (uint16_t) _sclDirReg, HEX);
Ser.print(F(" _sdaPinReg = "));
Ser.println( (uint16_t) _sdaPinReg, HEX);
Ser.print(F(" _sclPinReg = "));
Ser.println( (uint16_t) _sclPinReg, HEX);
Ser.print(F(" line state sda = "));
Ser.println(i2c_sda_read());
Ser.print(F(" line state scl = "));
Ser.println(i2c_scl_read());
#ifdef ENABLE_I2C_SCANNER
// i2c_scanner
// Taken from : http://playground.arduino.cc/Main/I2cScanner
// At April 2015, it was version 5
Ser.println("\n I2C Scanner");
byte error, address;
int nDevices;
Ser.println(" Scanning...");
nDevices = 0;
for(address=1; address<127; address++ )
{
// The i2c_scanner uses the return value of
// the Write.endTransmisstion to see if
// a device did acknowledge to the address.
beginTransmission(address);
error = endTransmission();
if (error == 0)
{
Ser.print(" I2C device found at address 0x");
if (address<16)
Ser.print("0");
Ser.print(address,HEX);
Ser.println(" !");
nDevices++;
}
else if (error==4)
{
Ser.print(" Unknow error at address 0x");
if (address<16)
Ser.print("0");
Ser.println(address,HEX);
}
}
if (nDevices == 0)
Ser.println(" No I2C devices found\n");
else
Ser.println(" done\n");
#endif
}
