CY7C65215A holds I2C (SCB0) bus low until USB connected

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BeUh_3903566
Level 2
Level 2

I am using a CY7C65215A as a USB - I2C bridge acting as the I2C master. If I power my system on without USB connected to the 215A, the 215A holds my I2C lines low.

After I connect USB to the 215A, I see some activity on the I2C lines for a few seconds (driven by 215A), and then it lets go of the lines and they are pulled high. After the lines are pulled high, I can disconnect the USB from the system and the I2C lines are still inactive (pulled high).

Any thoughts on why this is happening?

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1 Solution

Hello,

Apologies for the delay in response. If the pull up resistors are powered using 1.8V, then the I2C lines should be held high even before USB is connected. I tried reproducing the issue when the device(CY7C65215) is self powered in our DVK, and configured as an I2C master device and both the SCL and SDA lines are high as soon as external supply is provided and stay high after USB is also connected. Please check if the internal 1.8V regulator is disabled in the USB Serial Configuration Utility since you are providing the same on VDDD.

Best Regards,

Sananya

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Sananya_14
Moderator
Moderator
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750 replies posted 500 replies posted 250 solutions authored

Hello,

Please share your schematic with us. Do you have a I2C slave device connected before the device is powered on and pull up resistors on the I2C lines?

Best Regards,

Sananya

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Sanaya,

See my schematic below. There are 2 I2C slave devices: an FPGA and a TCA9406 I2C level shifter, and has a 10k ohm pullup resistor.

I have built a small evaluation board with the same configuration on the 215A and I2C pullups, but no I2C slave on the bus, and the 215A exhibits the same behavior.

Thank you for the support.

pastedImage_0.png

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I'm posting this question again as a new topic since apparently that's the only way to get a response.

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Hello,

Apologies for the delay in response. If the pull up resistors are powered using 1.8V, then the I2C lines should be held high even before USB is connected. I tried reproducing the issue when the device(CY7C65215) is self powered in our DVK, and configured as an I2C master device and both the SCL and SDA lines are high as soon as external supply is provided and stay high after USB is also connected. Please check if the internal 1.8V regulator is disabled in the USB Serial Configuration Utility since you are providing the same on VDDD.

Best Regards,

Sananya

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