M5Dial external i2C (port A) with Arduino Wire

minieigi

I want to use a I2C CAN Bus Module https://docs.longan-labs.cc/1030017/ connected to the port A on the M5Dial.
The Longan_I2C_CAN_Arduino lib uses the Arduino Wire lib.
I get the following error probably because It uses the internal I2C.

Guru Meditation Error: Core  1 panic'ed (IllegalInstruction). Exception was unhandled.
Memory dump at 0x4200f55c: e2e502ad 000000ff fd004136
...

in the main.ino file I declare a second Wire instance and initialize it with the pins used on the M5Dial.

TwoWire i2Ctwo(2);
I2C_CAN CAN(0x25, &i2Ctwo); // Set I2C address and Wire instance 

void setup() {
  int8_t SDA_2 = M5.Ex_I2C.getSDA(); // 2 (G13)
  int8_t SCL_2 = M5.Ex_I2C.getSCL(); // 3 (G15)
  i2Ctwo.begin(SDA_2, SCL_2);
...

But the M5Dial class uses already the I2C_Class instead of the TwoWire class.

// for external I2C device (Port.A)
   I2C_Class &Ex_I2C = m5::Ex_I2C;

I modified the I2C_CAN lib to be able to pass a TwoWire * pointer.

I2C_CAN::I2C_CAN(unsigned char __addr, TwoWire *__i2c = &Wire)
{
    IIC_ADDR = __addr;
    i2C = __i2c;
}

void I2C_CAN::begin()
{
    i2C->begin();
}

void I2C_CAN::IIC_CAN_SetReg(unsigned char __reg, unsigned char __len, unsigned char *__dta)
{
    i2C->beginTransmission(IIC_ADDR);
    i2C->write(__reg);
    for(int i=0; i<__len; i++)
    {
        i2C->write(__dta[i]);
    }
    i2C->endTransmission();
}
...

Has anyone tried to use a I2C extension on port A with a standard Arduino lib? Any help would be appreciated.

felmue

Hello @minieigi

have you tried to simply use Wire? E.g.

//  i2Ctwo.begin(SDA_2, SCL_2);
  Wire.begin(SDA_2, SCL_2);

In addition you could also try to first release/end the predefined Wire:

  M5.Ex_I2C.release();

Thanks
Felix

minieigi

If I leave the Longan_I2C_CAN_Arduino lib unchanged I get one CAN message before the device reboots and I see the error I posted above.
It seems the standard Wire pins are configured properly.
If I add Wire.begin(2, 3) the device is not even starting Serial debug.
M5.Ex_I2C.release(); is not making any difference.

felmue

Hello @minieigi

you are correct, the standard Wire pins are configured correctly for port A, but in your case you don't want the I2C_Class wrapper from M5Unified. So the idea is to release/end Wire as it has been initialized in M5.begin() and then restart Wire by calling Wire.begin(13, 15).

And yes, I think the release() is done automatically when Wire is re-initialize.

Note: I don't have this particular sensor so I cannot fully test this myself.

Thanks
Felix