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I'm trying to connect my energy measurement IC with Raspberry Pi 3B using the I2C protocol. I'm using sudo i2cdetect -y 1 to detect the connected devices and it is correctly showing the address(7-bits) of the connected IC. The IC contains a various registers of 8,16,24 and 32-bits. The register addresses are 16-bits long and I'm using the following code to access a register 0x021C(24-bits) and write registers 0xFE(8-bit) and 0x0120(16-bit)

Python Code

from smbus2 import SMBus

bus = SMBus(1)

address = 0x38

bus.write_byte_data(address,0xFE,0xAD)  #Writing single byte of data
bus.write_i2c_block_data(address,0x120,[0x00,0x30])  #Writing multiple bytes of data to the register
block = bus.read_i2c_block_data(address,0x21C,3)  #Reading multiple bytes of data from the register
print(block)

bus.close()

The output should be [0x8D,0xXX,0xXX] but the code is producing output as [0,0,0]

  • Question-1: Is giving 16-bit address allowed in this Library or not?
  • Question-2: If allowed then why the code is not working?

Any help would be much appreciated

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  • You seem to be using "read block". I vaguely remember that requires "bus stretching".
    – tlfong01
    Jul 8, 2022 at 2:46

1 Answer 1

Reset to default
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All I2C parameters are 8-bit.

To send a 16-bit value you must send two 8-bit values.

To send a 24-bit value you must send three 8-bit values.

You must also send the values in the order expected by the device. This may be least significant value first or most significant value first.

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3
  • I've tried what you are mentioning but the functions only accept only integer values for the register address. read_block_data(i2c_addr, register, force=None) Read a block of up to 32-bytes from a given register. Parameters: i2c_addr (int) – i2c address register (int) – Start register force (Boolean) – Returns: List of bytes Return type: list
    – Satya Prakash Singh
    Jul 7, 2022 at 20:09
  • I suggest you experiment with pigs. Only use i2co, i2crd, and i2cwd.
    – joan
    Jul 7, 2022 at 20:21
  • Take a look at adafruit blink library, similar to smbus but less protocol specific: in particular look at something like writeto_then_readfrom(address, buffer_out, buffer_in, *, out_start=0, out_end=None, in_start=0, in_end=None, stop=False), it might enable you to do what you are attempting
    – SEWTGIYWTKHNTDS
    Dec 4, 2022 at 19:09

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