MCT8316A: I2C bus communication cannot work

Tachibana Masanori

Part Number: MCT8316A
Other Parts Discussed in Thread: MCF8316AEVM, , MCF8316A

Hello support team,

We are trying to evaluate MCT8316AV in a motor drive circuit.
We configured the circuit shown below, but I2C bus communication can not work.

Even if MCU send start bit and target ID (00b) + R/W bit, MCT8316AV do not return ACK signal.
Is there any problem in the peripheral circuit of MCT8316AV?

I would appreciate any advice.

Best regards,
M. Tachibana

over 3 years ago

0 Vishnu Balaraj over 3 years ago

TI__Mastermind 24415 points

Hi Tachibana-san,

We reviewed the schematic and the external circuits over email and didn't find any issues. Are you able to communicate tot he MCT8316AEVM?

Regards,

Vishnu

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Balaraj-san

Thank you for your prompt response.

Yes, MCT8316AEVM can communicate with our MCU by I2C.
We've tried various ways, but we are in trouble because we don't understand the cause.

Best regards,
M. Tachibana

0 Aaron Barrera over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 26046 points

Hi Tachibana-san,

Vishnu will get you a reply tomorrow.

Thanks,
Aaron

0 Vishnu Balaraj over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 24415 points

Hi Tachibana-san,

We noticed that the FG (pin 29) is pulled to GND. This could cause the I2C not to work. Can you pull FG to 3.3V via 5k resistor and try again?

Regards,

Vishnu

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Vishnu-san,

Thank you for your reply.

Does FG (pin 29) related to the I2C communication function?
We have not tried pulling up FG on our board yet.
But we have already confirmed that the I2C bus can communicate normally even if the FG pin of MCT8316AEVM is pulled down to GND.

Best regards,
M. Tachibana

0 Tachibana Masanori over 3 years ago in reply to Tachibana Masanori

Prodigy 100 points

Hi Vishnu-san,

Let me ask you additional questions.

Do we have to pull up FG pin to 3.3V (or 5V)?
Does I2C communication work stably even if FG pin is left open without pulling up to high level?

Please give us your advice.

Best regards,
M. Tachibana

+1 Vishnu Balaraj over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 24415 points

Did you follow the below steps?

1. Connect FGOUT to AGND as shown in below figure

2. Turn ON the power supply

3. Wait for the GUI to connect to the MSP430. You should see “Hardware connected” at the bottom left of the GUI.

4. Click “View all tuning settings” and click “Read all registers”. You will see a window pop up showing “Connectivity issue”

This confirms that there will be I2C communication issue when FG is pulled to GND.

Regards,

Vishnu

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Vishnu-san,

Thank you for your advice.

We understood the procedure to check, and confirmed again using MCT8316AEVM.
And we confirmed that I2C communication stopped when FG pin is connected to GND.

Our current development board has no wiring pattern for connecting external components to FG pin, so it difficult to pull up FG pin. If there is no problem, we would like to evaluate the board with FG pin left open.
So we want to know FG pin has to be pulled up.
Also, we would like to know whether the pull-up voltage should be only 3.3V, or it is ok with 5V.

Best regards,
M. Tachibana

+1 Vishnu Balaraj over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 24415 points

Tachibana-san,

No, we recommend not to leave the FG pin floating as we might still see I2C communication issue. It should be pulled to 3.3V or 5V.

Regards,

Vishnu

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Vishnu-san,

Ok, we will pull up FG to Vcc.
We also understood that I2C communication stops when FG is pulled down to 'L' level.

By the way, FG pin outputs 'H' / 'L' pulse according to the speed of the motor.
When FG outputs 'L' level, doesn't I2C communication stops by the signal of FG itself?

Best regards,
M. Tachibana

+1 Vishnu Balaraj over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 24415 points

Tachibana-san,

FG is an open drain pin and the logic is controlled by the internal FET based on the motor speed. We will not see I2C communication issue when the Internal FET pulls this pin to GND.

Regards,

Vishnu

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Vishnu-san,

Sorry to late reply.

I understood that internal FET would not be bad influence on I2C communications.

Our EVM we confirmed at the first was MCF8316AEVM, and PMCF8316 was mounted on it. And it's target ID was 0x60 not 0x01.
I2C communication worked well even if FG pulled to GND externally on our MCF8316AEVM.

Regarding the I2C communication issue, is there any difference between MCT8316A and (P)MCF8316A?

Thanks and best regards,
M. Tachibana

+1 Vishnu Balaraj over 3 years ago in reply to Tachibana Masanori

TI__Mastermind 24415 points

There is no difference in I2C (except I2C target address) between MCT8316A and (P)MCF8316A. Since the I2C communication issue is now resolved, can we close this thread?

0 Tachibana Masanori over 3 years ago in reply to Vishnu Balaraj

Prodigy 100 points

Hi Vishnu-san,

I understand.
Thank you for your support.

Best regards,
M, Tachibana

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MCT8316A: I2C bus communication cannot work