Linux/SN65DSI86EVM: 3.3 V I2C bus perturbated by 1.8 V I2C bus

Jean Sannac

Part Number: SN65DSI86EVM
Other Parts Discussed in Thread: SN65DSI86

Tool/software: Linux

Hello,

I am currently working on SN65DSI86 EVM and I try to configure this board with a 3.3 V I2C bus. When I connect this bus trough J10 connector without I2C_3V3EN I am able to read the state of the component TSL2561T so my bus works.

But by default, the 1.8 V I2C bus is in low state, so when I enable I2C_3V3EN, my SDA and SCL lines are in undefined state (~1V) and my bus doesn't work anymore. I want the SN65DSI86 to be slave in the bus but I got the feeling that this component forced the bus level. Is that normal that the 1.8 V I2C bus affects my 3.3 V I2C bus with it low state? Do we require specific configuration to put the SN65DSI86 in slave mode?

I must miss some configurations but I didn't find anything on the datasheet that could help me understand.

Thanks for your help.

over 6 years ago

0 David (ASIC) Liu over 6 years ago

TI__Guru**** 179171 points

Jean

What is the state of ADDR and EN? Can you also please check to make sure BOARD_1P8V is 1.8V?

Thanks
David

0 Jean Sannac over 6 years ago in reply to David (ASIC) Liu

Prodigy 45 points

Hello David,

Thanks for your quich response.

BOARD_1P8V is almost 1,8V (1.786 V), ADDR is HIGH (1.786 V) so the address must be 0x2D and EN is HIGH but with lower voltage 1,54 V. I tried to change ADDR state and EN but my problem remain, when I enable I2C_3V3EN, SCL_3P3V fall to 1,4 V and SDA_3P3V to 1 V.

Jean

0 David (ASIC) Liu over 6 years ago in reply to Jean Sannac

TI__Guru**** 179171 points

Jean

Please give me couple days and let me see if I can duplicate the issue on the EVM in the lab.

Thanks
David

0 Jean Sannac over 6 years ago in reply to David (ASIC) Liu

Prodigy 45 points

Hello David,

Any update from your side? Even when I just powered the EVM with nothing plugged in and I2C_3V3EN disable, I have the same behaviour, I2C_SDA and I2C_SCL (1,8 V) are around 0,4 V. Is that normal? I suspect that something goes wrong with my component.

Thanks.

Jean

0 David (ASIC) Liu over 6 years ago in reply to Jean Sannac

TI__Guru**** 179171 points

Jean

Sorry for the delay, I verified on my EVM for both the I2C_3V3EN disabled or enabled case, the I2C_SDA and I2C_SCL are 1.8V. You probably have faulty board that needs to be replaced.

Thanks

David

0 Jean Sannac over 6 years ago in reply to David (ASIC) Liu

Prodigy 45 points

Hello David,

Thanks for your support, I also think that my board is faulty, I will see what I can do.

Regards.

Jean

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Linux/SN65DSI86EVM: 3.3 V I2C bus perturbated by 1.8 V I2C bus