LP5024EVM: I2C NAKing

Hi Evan,

It looks like there are 4 wires here. I think the blue and purple is for SDA and SCL. I wonder that what the white one and green one are for?

BR, Jared

Hi Jared,

Yes, the purple is SCL and blue is SDA. There are three others: The green is 5V coming from the microcontroller board, there is a wire underneath it connected to ground, and the white wire is the EN pin which is connected to a GPIO pin on the microcontroller board and is being set to high (shown in my code above). I was trying different setups with powering and changing J6 to try to get the EVM board to ACK, but I haven't found the setup that works for me yet.

Hope this helps!

Thanks,

Evan

Hi Evan,

I have tried 0x3C as the slave address to control LP5024 in broadcast mode. it can work on my EVM. So, I think it's not the hardware problem. So I suggest you to try the actions below:

1. Please try to check the power of device, such as VCC, VCAP, VMCU, VLED.

2. Please refer my hardware connection below first and try to send your command.

3. Please try to change your slave address to 0x28 by controlling board in standalone mode to check if there is any ACK from board.

BR, Jared

Hi Jared,

I matched your jumpers you sent above and checked the voltages VCC, VMCU, and VLED and they are all at 5V. I tried both 0x3C and 0x28 as the slave address and I am still not getting an ACK. I double checked that the device was still working by using the USB2ANY setup and it does indeed work. Any other ideas I could try to get this working?

Thanks,

Evan

Hi Evan,

Can you please measure the duration period of CLK high level?

BR, Jared

Hi Jared,

The high duration on SCL is 750ns

Thanks,

Evan

Here is a screenshot of the waveform with some measurements.

Hi Evan,

I think it doesn't make sense. Please give me some days to simulate your signal in my office.

BR, Jared

Hi Jared,

Would you mine sending me a picture of what the waveform should look like? Is there something wrong with the waveform I sent? Should I see an ACK?

Thanks,

Evan

Hi Evan,

Here is the waveform I captured, the T1, T2, T3 are just like your P0, P1, P2. Hope it can help you.

Thanks and BR,

Jared

Hi Jared,

Does my I2C waveform look correct? Should I be getting an ACK?

Thanks,

Evan

Hi Evan,

I think your I2C signal is correct and you should get the ACK. Can you please tell me the I2C waveform is from your software or from the board? If it's only from your MCU, please capture the I2C waveform from the board.

BR, Jared

Hi Jared,

I believe I discovered the issue. Here is a screenshot comparing the I2C coming from the USB2ANY (in white) versus the I2C from my microcontroller board (in color)

As you can see, it looks like the I2C data is shifted by one bit when comparing the SDA lines. I'm wondering why this is the case? It looks like the USB2ANY is transferring 0x50 as a slave address instead of 0x28. This is not what is specified in the LP5024 datasheet. Any ideas on this?

Thanks,

Evan

Both of these were monitored on R1 and R2 on the EVM board by the way.

Hi Evan,

I think it doesn't make sense. If the I2C data is shifted by one bit, I think the SDA falling edge will be shifted one bit too.

1. I want to make sure the white signals are from the board side and the color signals are from the MCU, am I right?

2. Could you please tell me how you connect your MCU to the board? Is there something between them?

BR, Jared

Hi Jared,

1. ALL of the signals shown were measured by probing the EVM board at resistors R1 and R2. The white signals were what was measured with the USB2ANY connected and the colored signals were what was measured with the micro board connected.

2. I have wires connecting the micro board and the EVM board directly, there is nothing between them.

Hope this helps, let me know if you have more questions.

Thanks,

Evan

Hi Jared,

This fixed my issue. Thanks for the help!

Best,

Evan

Hi Evan,

Glad to help you!

BR, Jared