SN65DSI84: I2C address for Read/Write using Aardvark

Rangarajan Krishnamachari

Part Number: SN65DSI84
Other Parts Discussed in Thread: SN65DSI85

Hello,

I was able to communicate with the SN65DSI85 EVM using I2C address 0x2D and now I am trying to communicate using the I2C from a microcontroller. I get an io bus address failure when I use 0x2D as the I2C address. Can you confirm?The datasheet (sec 7.5.1 Local I2C interface overview) mentions that the Addr = 1, the address cycle is 0x5A (write) and 0x5B (read) but I dont set these address with Aardvark and I am able to read correctly from the EVM. Can you confirm if I'm missing something?

Thanks

Ranga

over 7 years ago

0 Ikechukwu Anyiam over 7 years ago

TI__Mastermind 35130 points

Hi Rangarajan,

We will look into your issue and get back to you by tomorrow.

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hi I.K.,

Do you have any suggestions?

Thanks

Ranga

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

Sorry for the delay, I was tied up yesterday.

It looks like your microcontroller may be ignoring bit 0, the W/R bit. Can you try shifting the i2c address to the left by 1 bit with your microcontroller? You didn't need to do that with the Aardvark since it does it by itself.

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hi I.K.,

I checked the waveform with the micro-controller and it does shift the address to the left but I still get IO address failure, I am trying if there is any other timing violation that might be causing this issue? I have included a scope plot with the NAK.

0 Rangarajan Krishnamachari over 7 years ago in reply to Rangarajan Krishnamachari

Intellectual 280 points

Hello I.K.,

I capture the plot with Aardvark and I find that the data with the micro-controller is about 1/4 cycle delayed compared to the plot captured with Aardvark. Can you confirm if the data from my micro controller is violating any timing spec requirement?

Thanks

Ranga

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

What microcontroller are you using? Can you try selecting the other target address?

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hi I.K.,

We have an internal tool where I can use send commands from PC through USB and the ARM micro controller (TI LM3S9B96_BGA108) would send the commands through I2C to the EVM.

Thanks

Ranga

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

Have you tried the other target address (0x2C, or 0x58 with the shift)?

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hi I.K.,

Same issue with other I2C address as well. You do not see any timing violations with the previous I2C transactions that I had posted? Any other suggestions that I can try or test?

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

From the first provided waveform it looks like there actually may be a rise/fall time violation. The maximum is 300ns. You can reference the fast-mode timing parameters in the table below:

Regards,

I.K.

0 Ikechukwu Anyiam over 7 years ago in reply to Ikechukwu Anyiam

TI__Mastermind 35130 points

Hi Ranga,

Has this been resolved? Are you still having issues?

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hello I.K.,

I measured the rise/fall time again @ 400kHz and it does not seem to violate the timing spec, I'm still debugging the issue to find what might be causeing the "IO address failure".

0 Rangarajan Krishnamachari over 7 years ago in reply to Rangarajan Krishnamachari

Intellectual 280 points

Hello I.K.,

Do you have any local support in the bay area who can help us debug the root cause? We plan to build 50boards with the SB65DSI85 ICs on and want to make sure that we can use our micro-controller to talk to the device rather than Aardvark.

Thanks
Ranga

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

I would suggest posting this issue to the microcontroller section of this forum instead since the issue seems to be related to the MCU configuration: e2e.ti.com/.../

Regards,
I.K.

0 Rangarajan Krishnamachari over 7 years ago in reply to Ikechukwu Anyiam

Intellectual 280 points

Hi I.K.,

It looks like the level shifter on the EVM was messing up the communications with the micro-controller. I bypassed the level shifter and was able to talk to the device directly with my setup @ 1.8V.

Thanks for your help.
Ranga

0 Ikechukwu Anyiam over 7 years ago in reply to Rangarajan Krishnamachari

TI__Mastermind 35130 points

Hi Ranga,

I'm glad you were able to resolve the issue, and thanks for posting what the solution was for potential future cases.

Regards,
I.K.

Interface

Interface forum

SN65DSI84: I2C address for Read/Write using Aardvark