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Posts: 4
Registered: ‎08-28-2017

CPT112S - I2C not working

Hello,

 

 

I'm trying to work with CPT112S evaluation board and STM32 Nucleo 446RE, tried both the default device address(0xE0) and changed it to other address, i cannot get ACK from the device.

 

Tried to wake-up the device during the I2C still - device does not answer.

 

Am i missing something?

 

 

Is there any way to get RAW data from proximity touch buttons instead of slider/button events?

 

Thanks.

Posts: 562
Registered: ‎09-18-2015

Re: CPT112S - I2C not working

Hi @Itamare,

 

I'm trying to work with CPT112S evaluation board and STM32 Nucleo 446RE, tried both the default device address(0xE0) and changed it to other address, i cannot get ACK from the device.

 

You do know that the CTPS112 is designed only to work with Silicon Labs' I2C and that it will fry any other vendor's connected device Smiley Happy

 

All kidding aside, there are two likely culprits:

 

  1. Don't forget the pull-ups on SDA and SCL.
  2. Is there any chance your STM32 device does some manipulation of the I2C address, e.g. automatically left-shifting it or reversing the bit order?

    Once you know your pull-ups are working, probe SDA to see what address is actually getting shifted out of your STM32.

 

Is there any way to get RAW data from proximity touch buttons instead of slider/button events?

 

No. The whole purpose of our CPT family of devices is to eliminate the need to process raw touch data and recognize events.

 

John

Posts: 4
Registered: ‎08-28-2017

Re: CPT112S - I2C not working

Thanks @JohnB

 

I tried both of the given solutions: with pull-ups on SDA and SCL, checked it with scope address looks good, device still does not response, first i check the INT, than try to read from the device still not ACK.

 

 

Do Silicon labs have a proximity device with access to RAW data? i am looking for a replacement for the good old MPR121.

 

 

 

thanks.

Posts: 562
Registered: ‎09-18-2015

Re: CPT112S - I2C not working

Hi @Itamare,

 

What does your schematic look like? If you see valid signal levels from the master device, then the CPT112S probably isn't responding because it's not running the firmware as expected, meaning you probably have something connected improperly.

 

Do Silicon labs have a proximity device with access to RAW data? i am looking for a replacement for the good old MPR121.

 

No. You buy a CTP112S specifically because it's firmware eliminates the need to mess with the raw data.

 

If you want to process raw data, you can do that with your STM32 MCU, or, better yet look at our Pearl Gecko 12 or Giant Gecko 11 devices, which integrate our patented capacitive touch sensing technology and run our highly accurate cslib firmware.

 

John

Posts: 4
Registered: ‎08-28-2017

Re: CPT112S - I2C not working

 

Appreciate your help, sorry for the late response,

Schematic is pretty easy - SDA/SCL with pull-up resistors to 3.3V, connected to the STM32 MCU.

 

Maybe the firmware i'm using is not the correct one?

 

 

I set the Simplicity Studio as follow:

I2C.png

 

Is it the correct definitions?

 

 

Thank you.

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Posts: 562
Registered: ‎09-18-2015

Re: CPT112S - I2C not working

Hi @Itamare,

 

You are attempting to communicate with the CPT112S when it has asserted the EB_INT pin, right? That's the only time the device will respond, otherwise it will just NAK any transmission it receives.

 

John

Posts: 4
Registered: ‎08-28-2017

Re: CPT112S - I2C not working

Hi @JohnB,

 

Yes. I am trying to run it only when the INT is triggered.