Confusing overload of Wire::begin

[Equidamoid]

Board

Any

Device Description

Not specific to a device.

Hardware Configuration

Any I2C device connected

Version

v2.0.2

IDE Name

CLion + platformio

Operating System

Linux

Flash frequency

N/A

PSRAM enabled

no

Upload speed

N/A

Description

The Wire::begin method has confusing overload:

    bool begin(int sda=-1, int scl=-1, uint32_t frequency=0); // returns true, if successful init of i2c bus
    bool begin(uint8_t slaveAddr, int sda=-1, int scl=-1, uint32_t frequency=0);

The sda and scl arguments are of type int, while the SDA and SCL constants from d32_core.h have type uint8_t. A "naive" user might try to call begin(SDA, SCL) and get mysterious "could not acquire lock" error on first attempt to use the bus.

To make the problem worse, this code worked fine before the "slave" overload was introduced.

As a solution I want to propose renaming the "slave" function to something like begin_slave.

Sketch

int setup(){
    // have to explicitly specify the pins to provide the frequency
    Wire.begin(SDA, SCL, 4000);
    Wire.beginTransmission();
}

Debug Message

[   238][E][Wire.cpp:319] beginTransmission(): could not acquire lock
[   239][E][esp32-hal-i2c.c:142] i2cWrite(): could not acquire lock

### Other Steps to Reproduce

_No response_

### I have checked existing issues, online documentation and the Troubleshooting Guide

- [X] I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[me-no-dev]

You can also:

Wire.begin();
Wire.setClock(frequency);

[StickStackxD]

You can also:

Wire.begin();
Wire.setClock(frequency);

I can confirm that the workaround is working for now.

[Equidamoid]

@me-no-dev
I came up with this (I know, ugly, but at least straightforward):

Wire.begin(static_cast<int>(SDA), static_cast<int>(SCL), static_cast<uint32_t>(4000));

[me-no-dev]

casting also works, but I do see this as a kind of issue :) we will have to "fix" this somehow

[mymy-dot]

This issue ended up taking me several hours to solve, until by chance I came across this post. Granted, I don't know what I'm doing. But I do know that adding:

Wire.begin(static_cast<int>(SDA), static_cast<int>(SCL), static_cast<uint32_t>(4000));

Made the beginTransmission(): could not acquire lock error go away on my ESP-WROOM-32 and I was able to access my I2C device.

[bato3]

This is because SDA and SCL are defined as

static const uint8_t SDA = 21;
static const uint8_t SCL = 22;

and Wire.begin() can be:

    bool begin(int sda=-1, int scl=-1, uint32_t frequency=0); 
    bool begin(uint8_t slaveAddr, int sda=-1, int scl=-1, uint32_t frequency=0);

And some libriares defines it initializations as:

   bool     begin(uint8_t sda = SDA, uint8_t scl = SCL, uint32_t speed = AHTXX_I2C_SPEED_100KHZ, uint32_t stretch = AHTXX_I2C_STRETCH_USEC);

Working solutions

  Wire.begin((int) SDA , (int) SCL);
  Wire.begin(21, 22);
  Wire.begin();

Not working solutions:

Wire.begin(0x38, (int) SDA, (int) SCL);
Wire.begin((uint8_t) -1, (uint8_t) -1); // display error:
//i2cSlaveInit(): invalid pins sda=-1, scl=22

Another affected: esphome/esphome#2978

[SuGlider]

I see some other conflict with overload of Wire::begin():

Wire.begin(SDA, SCL, 40000) will end up in I2C Slave initalization... This is a Regression Issue!

[   102][E][esp32-hal-i2c-slave.c:224] i2cSlaveInit(): invalid pins sda=9, scl=-128
[   109][E][Wire.cpp:168] begin(): Slave Init ERROR

I also noticed that it is necessay to force the right overload by using something like:

Wire.begin(SDA, SCL, (uint32_t)40000);   //  casting forces it to be MASTER

By other hand, a typical Arduino Slave initialization such as
Wirebegin(0x34);
will end up in a I2C MASTER initialization - also confusing because this is the Arduino I2C Slave deafult setup.

In order to force Slave setup, it is necessary to use a type casting again...

Wire.begin((uint8_t)0x34);   //  casting forces it to be SLAVE

@me-no-dev - would you consider changing all of it to the default Arduino way Wire::begin()/Wire::begin(uint8_t) and only expose Wire::setClock() and Wire::setPins() for an Arduino Core 2.1.0, for instance?

I think it may be a good way to "start over" and solve it for good.

[SuGlider]

@me-no-dev - Please evaluate the proposed solution in #7000

[SuGlider]

#7000 makes all those cases to work fine:

  // I2C MASTER Test Cases
  Serial.println("\nUC 1.1 - Master - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin();

  Serial.println("\nUC 1.2 - Master - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin(-1, -1);
  
  Serial.println("\nUC 1.3 - Master - default SDA/SCL pins, 1KHz bus");
  Wire.end(); Wire.begin(-1, -1, 1000);
  
  Serial.println("\nUC 1.4 - Master - default SDA, SCL pin 2, 2KHz bus");
  Wire.end(); Wire.begin(-1, 2, 2000);
  
  Serial.println("\nUC 1.5 - Master - default SDA/SCL pins, 400KHz bus");
  Wire.end(); Wire.begin(SDA, SCL, 400000);
  
  Serial.println("\nUC 1.6 - Master default SDA pin 8, SCL pin 9, 800KHz bus");
  Wire.end(); Wire.begin(8, 9, 800000);
  
  Serial.println("\nUC 1.7 - Master - SDA pin 8, SCL pin 9, default 100KHz bus");
  Wire.end(); Wire.begin(8,9);
  
  Serial.println("\nUC 1.8 - Master - SDA pin 10, SCL pin 11, 200KHz bus");
  Wire.end(); Wire.begin(SDA_1, SCL_1, 200000);
  
  Serial.println("\nUC 1.9 - Master - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin(SDA, SCL);
  
  Serial.println("\nUC 1.10 - Master - default SDA/SCL pins, 4KHz bus");
  Wire.end(); Wire.begin(-1, -1, 4000);
  
  Serial.println("\nUC 1.11 - Master - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin((int) SDA , (int) SCL);

  // I2C SLAVE Test Cases
  Serial.println("\nUC 2.1 - Slave - ADDR 0x28 - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin(0x28);
  
  Serial.println("\nUC 2.2 - Slave - ADDR 0x21 - default SDA/SCL pins, default 100KHz bus");
  Wire.end(); Wire.begin(SLV_ADDR);
  
  Serial.println("\nUC 2.3 - Slave - ADDR 0x21 - default SDA/SCL pins, 4KHz bus");
  Wire.end(); Wire.begin(SLV_ADDR, -1, -1, 4000);
  
  Serial.println("\nUC 2.4 - Slave - ADDR 0x38 - SDA 10, SCL 11, default 100KHz bus");
  Wire.end(); Wire.begin(0x38, SDA_1, SCL_1, 0);
  
  Serial.println("\nUC 2.5 - Slave - ADDR 0x38 - default SDA/SCL pins, 4KHz bus");
  Wire.end(); Wire.begin(0x38, -1, SCL, 4000);