ONET4291VA: I2C address select

Izik

Part Number: ONET4291VA

Hello

Can you please advise how do I select the address bits value for the I2C protocol. Usually there are external pins which can be connected to PU or PD.

Thanks

over 2 years ago

0 Nasser Mohammadi over 2 years ago

TI__Guru* 93670 points

Greetings,

This device uses 2-wire interface and SCL and SDA requite PUs. Please note data sheet 2-wire serial interface and control logic section. Additionally note E2E link below with scope shots and more details:

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/703347/onet4291va-serial-interface?tisearch=e2e-sitesearch&keymatch=onet4291va%2520i2c#

Regards,Nasser

0 Clemens Ladisch over 2 years ago

Guru 317250 points

This device does not use I²C. There is no device address, and there are 13 bits between START and STOP, without an ACK bit.

You cannot use the I²C hardware of your microcontroller. The SDA/SCL lines should be connected to two separate GPIOs (and they should not be open drain).

0 Izik over 2 years ago in reply to Nasser Mohammadi

Expert 1585 points

Hello and thank you for the answer

I understand the I2C protocol. But how do I determine the specific device address?

0 Nasser Mohammadi over 2 years ago in reply to Izik

TI__Guru* 93670 points

There is not a device address and this is why it is called 2-wire interface.

After start, first three bits specifies register address and then we have 8 bits for register content. Please note the scope shot in the earlier response.

Regards,Nasser

0 Izik over 2 years ago in reply to Clemens Ladisch

Expert 1585 points

Hello

The data sheet specifically recommends using open drain output for these ports (page 3). Can you please advise.

0 Nasser Mohammadi over 2 years ago in reply to Izik

TI__Guru* 93670 points

Greetings,

Yes these are open drain IOs.

Regards,nasser

+1 Clemens Ladisch over 2 years ago in reply to Izik

Guru 317250 points

The SDA and SCK pins are CMOS inputs (they are not bidirectional). The only way to meet the required CLK_R, DTA_R timings is with a push/pull output.

I do not know why the datasheet mentions open-drain drivers; it would make sense for I²C, but not for this protocol.

0 Nasser Mohammadi over 2 years ago in reply to Clemens Ladisch

TI__Guru* 93670 points

Agreed.

Looking closely at the DC parametric table this is clearly specified. These are 2-levels CMOS IO with internal pull-ups. We should follow parametric table since part is tested against min/max of this table.

Regards,Nasser

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ONET4291VA: I2C address select