How to read data from device in I2C?

[espruino-discuss]

Posted at 2022-02-01 by user136941

Hello, I'm trying to figure out an error, when I realized that the problem is that I'm using wrong the I2C function. I need to read 8 bits from an address (0x75) in a i2c device (0x68). Following code is an example from libraries and docs:

I2C1.setup( {scl: NodeMCU.D4, sda: NodeMCU.D5} );

I2C1.writeTo(0x68,0x75);
var data = I2C1.readFrom(0x75,8);
console.log(data);

Got the next error:

Uncaught InternalError: I2CRead: No ACK 0
 at line 5 col 33
  var data = I2C1.readFrom(0x75,8);
                                ^
in function called from system

The readFrom function doesn't take as parameter the internal address of the device, that's why the error, is pointing to a device no to the internal address.

My device is an MPU9250, it works on Arduino and Micropython.

[espruino-discuss]

Posted at 2022-02-01 by @fanoush

There are three different device adresses used in your code -0x68,0x75,0x3b so which one is correct for your device?
Typically you first write register address you want to read from i2c.writeTo(0x68,regaddr) and then read (two=16bits) bytes i2c.readFrom(0x68,2)

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Posted at 2022-02-01 by user136941

Thanks, is already edited the device is 0x68 trying to read the register 0x75 or WHO_AM_I.

I didn't know that the second parameters accept Bytes.

Now its works, but the library MPU9250 don't work.