I2C ACK Question

giwonKIM · ‎2025-06-11

Hi, I bought the Nucleo-411RE board a few days ago, and try to test i2c protocol.

In this MCU's reference manual(RM0383) page 492,493, about I2C register CR1, Bit 10 ACK, It explains me that acknowledge returned after a byte is received(matched address or data).

Is it automatic? If my mcu received correct address, the mcu automatically returned ack by hardware?

I saw that HAL_I2C_Receive function but there is only bit setting about ack. No ack output instruction.

How return the mcu ack ? by hardware or software?

Thank you.

If you have any questions, please ask me.

Karl Yamashita · ‎2025-06-11

The slave returns the ACK. The HAL driver will return a status. If it returns HAL_ERROR, you'll have to get the error to figure what caused the error as it could be one of several things..

I was told that if a devices starts to smoke, put the smoke back in. I guess I never got all the smoke because the device never worked afterwards.
Don't worry, I won't byte.
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Saket_Om · ‎2025-06-12

Hello @giwonKIM

@giwonKIM wrote:
How return the mcu ack ? by hardware or software?

The ACK is sent by the hardware when a byte is received or an address match occurs.

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