Custom F446RE board fails with both reads and writes to I2C

Custom and community boards
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2

Hello,

Most Arduino users just copy&paste an example from internet and then just edit few things. Thanks to that they do not understand basics.

Your i2c address have to be bitshifted;

#define I2C_SHT40_ADDRESS 0x44<<1
//or
int i2caddress = 0x44<<1;

// 0x44h in binary 0010 1100b
// 0x88h in binary 0101 1000b
// 0x44h << 1 = 0x88h

If you do not do it like that then you need to do it in every read/write call.

You also can not use I2C methods like below

void SHT40::sampleLow(){
  i2c.start();
  ThisThread::sleep_for(10ms);
  if(i2c.write(0xE0)==1){        //Set: Read low precision (0xE0)
     i2c.read(i2caddress,SHT_DLC, 6);    // request 6 bytes from slave device #8
  }
  i2c.stop();
}

Overloaded method I2C::write() has two variants, so you can not combinate it like you did.

  • first one is for single byte transactions and Start/Stop have to be handled by you.
  • second one is for complet transaction and everything is managed by that method.

So just simple command should look like this with first method

  i2c.start();
  i2c.write(address); // i2c address bitshifted to left by 1
  i2c.write(0xE0);
  i2c.stop();

But much more better is with second one

void SHT40::sampleLow(){
  if(i2c.write(i2caddress,0xE0,1)==0){        //Set: Read low precision (0xE0)
     i2c.read(i2caddress,SHT_DLC, 6);    // request 6 bytes from slave device #8
  }
}

About the scaner function.
Like above the address have to be bitshifted.

void scanI2C() {
  for(int address=1;address<127;address++) {    
    int ack = i2c.write(address<<1, "0x94", 1); // address should be bitshifted
    if (ack == 0) {
       printf("\tFound at %3d - in 7bit %3x\r\n", address, address <<1);
    }    
    if(ack != 0){
        printf("I2C Error: %d\n", ack);
    }
    ThisThread::sleep_for(5ms);
  } 
}

BR, Jan