topic Re: I2C (smbus) level transceiver problem in Digital Signal Controllers

I2C (smbus) level transceiver problem

Gyosun — Tue, 20 Apr 2021 06:39:40 GMT

Hello,

I am using the AR8035 phy connected to the LS1046A custom board.

I am using PCA9517 for level conversion between cpu(1.8v) and phy(3.3v).

After applying the power and after a certain period of time, ifconfig fm1-mac3 down/up, there was a phenomenon that the up did not work, and when I checked it, I found that there is a problem with the level converter between the cpu and the phy.

There was no problem after testing after replacing PCA9617 as a pin compatible replacement.

When I take the waveform, there seems to be no difference as follows, but PCA9517 is fail and PCA9617 is pass, but I cannot find a clear cause, so I ask a question.

Can I use PCA9517, which was reviewed as a replacement from a long-term perspective,
If so, I would like to know the answer for what reason was solved.

Please understand that the translation is not smooth.

Thank you,

Best Regards,

Gyosun.

Re: I2C (smbus) level transceiver problem

ufedor — Tue, 20 Apr 2021 07:30:33 GMT

Provided traces are not clear enough.

Please provide them in full resolution.

Re: I2C (smbus) level transceiver problem

Gyosun — Tue, 20 Apr 2021 07:40:56 GMT

Re: I2C (smbus) level transceiver problem

ufedor — Tue, 20 Apr 2021 07:59:54 GMT

PCA9617 has significantly higher operation frequency - refer to the presentation:

https://www.nxp.com/video/nxp-semiconductors-i2c-pca9517-to-pca9617:NXP-I2C-PCA9517-TO-PCA9617

It is required to lower MDC frequency to 400 kHz for PCA9517.

Re: I2C (smbus) level transceiver problem

Gyosun — Tue, 20 Apr 2021 08:52:35 GMT

Hi ufedor,

Thank you for quick response.

When using 9517, I had symptoms even if I lowered the A/B side pull-up resistance to 1.5k and the MDC clock to 245khz.

Can't I use 9517 for smbus? Which part is the problem in terms of the waveform above?

The decision to replace is being delayed because the cause is unknown.

Any suggestion of a clear solution would be appreciated.

Thank you.

Best Regards,

Gyosun.

Re: I2C (smbus) level transceiver problem

ufedor — Tue, 20 Apr 2021 10:47:45 GMT

Please point on provided traces which exactly problem happens with PCA9517.

Re: I2C (smbus) level transceiver problem

Gyosun — Thu, 22 Apr 2021 02:54:55 GMT

Even if I lower the MDC to 245khz, problems arise.

AR8035 low input is 0.8v max and PCA9517 vol max is 0.6v.

It comes out up to 0.8v. Could the VOL level be an issue?

Re: I2C (smbus) level transceiver problem

ufedor — Thu, 22 Apr 2021 06:30:01 GMT

Please provide the PCA9517 connection schematics.

Re: I2C (smbus) level transceiver problem

Gyosun — Thu, 22 Apr 2021 08:03:38 GMT

I attach a schematic diagram.

Re: I2C (smbus) level transceiver problem

ufedor — Thu, 22 Apr 2021 08:33:12 GMT

Use 3kOhm resistors for R169 and R170.

Re: I2C (smbus) level transceiver problem

Gyosun — Thu, 22 Apr 2021 10:15:37 GMT

I changed it to 3kOhm, but nothing improved.

We will send you the measured waveform and test details.

Is vol a problem? Is there any way to lower it with a combination of resistance?

MDC is also set to 400khz or less so there should be no problems, but I don't know why?

Re: I2C (smbus) level transceiver problem

ufedor — Thu, 22 Apr 2021 10:33:47 GMT

Please disconnect EMI1_MDIO_3V3 from AR8035 and capture a trace.

Re: I2C (smbus) level transceiver problem

Gyosun — Thu, 22 Apr 2021 10:56:00 GMT

The MDIO was separated and captured from the AR8035.

Re: I2C (smbus) level transceiver problem

ufedor — Thu, 22 Apr 2021 16:53:57 GMT

Where exactly on the schematics the signal was probed?

Re: I2C (smbus) level transceiver problem

Gyosun — Fri, 23 Apr 2021 00:13:47 GMT

EMI1_MDIO_3V3 was separated from AR8035 and measured in 3kOhm pull-up state.

Re: I2C (smbus) level transceiver problem

ufedor — Fri, 23 Apr 2021 04:16:51 GMT

1) In the PCA9517 datasheet pull-up resistors are 10kOhm.

2) Have you compared traces at the AR8035 for proper and failing cases?

Re: I2C (smbus) level transceiver problem

Gyosun — Tue, 27 Apr 2021 11:22:04 GMT

1) In the PCA9517 datasheet pull-up resistors are 10kOhm.

I've tried it with 10kOhm, but it's the same symptom.

2) Have you compared traces at the AR8035 for proper and failing cases?

As a substitute, PCA9306 of other company was assembled and tested, and it worked normally.

However, since the board has already been built, we want the PCA9517 to work.

Re: I2C (smbus) level transceiver problem

ufedor — Tue, 27 Apr 2021 13:17:10 GMT

Have you tried to replace the PCA9517 by another PCA9517?

Re: I2C (smbus) level transceiver problem

Gyosun — Tue, 27 Apr 2021 23:57:33 GMT

I tried to replace it many times.

Re: I2C (smbus) level transceiver problem

ufedor — Wed, 28 Apr 2021 03:22:44 GMT

From the provided traces it is not clear where the problem moment is - i.e. data is identical.