TMP117: How to read ALERT pin output on Raspberry Pi

Christopher Galea

Part Number: TMP117

Hello,

I am planning to use I2C communication protocol between a TMP117 sensor and a Raspberry Pi 4B. To which pin on the Raspberry Pi should the ALERT pin of the TMP117 sensor be connected? It seems to be a separate line from the SDA and SCL lines.

Thanks in advance,

Chris

over 2 years ago

+1 Ren Schackmann over 2 years ago

TI__Mastermind 43805 points

Hi Chris,

You don't need to connect the ALERT pin. If you want to connect it to a GPIO pin, you can poll the pin to detect ALERT status.

thanks,

ren

0 Christopher Galea over 2 years ago in reply to Ren Schackmann

Prodigy 40 points

Hi Ren,

Thanks! Yes, I understand I don't need to connect the ALERT pin, but I wanted to monitor its output for testing purposes. Can it be connected to any GPIO pin on the Raspberry Pi?

Regards,

Chris

0 Christopher Galea over 2 years ago in reply to Christopher Galea

Prodigy 40 points

One follow-up question: If I have two TMP117 sensors, can I send both ALERTs to the same GPIO pin, or would they need to go to separate GPIO pins?

+1 Ren Schackmann over 2 years ago in reply to Christopher Galea

TI__Mastermind 43805 points

Yes, you can connect multiple TMP117 ALERT pins together. This is how SMBus Alert feature is intended to work. See 7.5.3.1.5 SMBus Alert Function in the datasheet.

ALERT is useful when you can configure a software interrupt. I don't recommend using ALERT if you can't configure an interrupt event for your GPIO. Otherwise, you will be querying the state of your GPIO in a loop that would be simpler if you were just querying the sensor using I2C.

ren

0 Christopher Galea over 2 years ago in reply to Ren Schackmann

Prodigy 40 points

Thanks again, Ren!

Regards,

Chris

0 Josh Wyatt over 2 years ago in reply to Christopher Galea

TI__Guru* 91206 points

Thanks for thanking Ren, Chris - closing this post. Please do feel free to post again if anything else comes up!

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TMP117: How to read ALERT pin output on Raspberry Pi