Custom TwoWire and begin()

[thijstriemstra]

#231 (1.14.0) added the option to use a custom TwoWire instance, which is great.

1.13.0 RTCLib's begin looked like this:

boolean RTC_DS3231::begin() {
  Wire.begin();
  Wire.beginTransmission(DS3231_ADDRESS);
  if (Wire.endTransmission() == 0)
    return true;
  return false;
}

it now looks like this:

boolean RTC_DS3231::begin(TwoWire *wireInstance) {
  RTCWireBus = wireInstance;
  RTCWireBus->begin();
  RTCWireBus->beginTransmission(DS3231_ADDRESS);
  if (RTCWireBus->endTransmission() == 0)
    return true;
  return false;
}

In my application I use custom SDA/SCL so I choose not to use RTC_DS3231::begin() but use my own that uses this begin call:

  // rtc
  Wire.begin(_sdaPin, _sclPin);
  Wire.beginTransmission(DS3231_ADDRESS);
  if (Wire.endTransmission() != 0) {
    Log.warning(F("Initializing DS3231... Error!" CR));
  }

In the latest version (1.14.0) I can't do this because begin now sets a protected var that I can't set from my code:

boolean RTC_DS3231::begin(TwoWire *wireInstance) {
  RTCWireBus = wireInstance;
  // etc..

I can also not use Wire.setPins(x, y) because the code still calls begin on Wire, which I want to do elsewhere.

So I'm stuck with 1.13.0. Any ideas how to work around this pesky situation?

cc @ubidefeo

[edgar-bonet]

Maybe add a parameter to the constructor for instructing it to skip the call to begin(). That parameter would default to false for backward compatibility:

In RTClib.h:

class RTC_DS1307 {
public:
  boolean begin(TwoWire *wireInstance = &Wire,
    boolean skip_begin = false);
  // ...
};

In RTClib.cpp:

boolean RTC_DS1307::begin(TwoWire *wireInstance, boolean skip_begin) {
  RTCWireBus = wireInstance;
  if (!skip_begin)
    RTCWireBus->begin();
  // ...
}

[ladyada]

we would not take either PR, its non-standard. for ESP32, folks can use i2c.setpins() espressif/arduino-esp32#3779