TCA9548A: NACK When Trying to Address Device

Ali

Part Number: TCA9548A

Tool/software:

Hello,

I am attempting to talk to the TCA9548A and can't seem to get an ACK after sending the device address.

The image below shows the SCL and SDA traces. The address of the device is 0x70 (0xE0).

This is the setup. I have confirmed that the 3 devices do not share the same address and the Ax lines match what is expected for the given addresses.

5 months ago

0 Clemens Ladisch 5 months ago

Guru 318700 points

Why are the two signals low at the beginning? The idle state of both I²C lines must be high, and they should not have a rising edge at the same time.

0 Ali 5 months ago in reply to Clemens Ladisch

Prodigy 10 points

Hey Clemens,

I changed my code so that the I2C lines are high and have confirmed they do not have a rising edge at the same time, but the result is the same.

Thanks.

0 Clemens Ladisch 5 months ago in reply to Ali

Guru 318700 points

Please show the schematic.

Why is the first rising edge of SDA so fast? Are you not using an open-drain output?

0 Ali 5 months ago in reply to Clemens Ladisch

Prodigy 10 points

The issue was an inadvertent pulling low of the reset line. Once I fixed that the part worked fine.

Thanks for your help.

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TCA9548A: NACK When Trying to Address Device