Pull down SDA pin i2c

[Hkhan7861]

Good day

I am developing on the nrf9160dk with a tag reader using i2c and am wanting to know if there is a function to pull down the SDA or SCL pins during operation in order to wake up the slave device.

Thank you in advance.

Kind regards,

Hassan

[Vidar Berg]

Hello,

Sorry, I'm not sure if I understand the question correctly. The timing of when the SDA  and SCL line are pulled low during transactions is defined by the i2c standard and handled by the HW in our TWIM peripheral (Ref. Two Wire Interface Master (TWIM) timing specifications).

Do you mean that your i2c slave device requires a non-standard wake-up sequence? If so, maybe you could provide me a link to the documentation where this sequence is described?

Best regards,

Vidar

[Hkhan7861]

Hi, thank you for the reply. This is the extent of what the documentation states.  Thank you !

6.1.1 Start condition Start is identified by a falling edge of serial data (SDA) while the serial clock (SCL) is stable in the high state. A Start condition must precede any data transfer command. The device continuously monitors (except during a write cycle) the SDA and the SCL for a Start condition, and does not respond unless one is given.

www.st.com/.../st25dv04k.pdf

[Vidar Berg]

OK, this is the standard way to start a transaction with i2c. Our TWIM peripheral will also create the start condition when you start a new transfer.

Have you tried to probe the SDA and SCL line with a logic analyzer to see what the problem is?

[Hkhan7861]

HI, do you mind sending the name or a link to that function so I may see how it works.  I can't seem to find it

Yes, I have used instruments to test and have found that by using an internal pull-up resister, the pin signal level doesnt drop enough.

[Vidar Berg]

The transaction is handled in HW, and not in SW.  Please see the "Master write sequence" section of the TWIM chapter for more details on how this works.

Hkhan7861 said:

Yes, I have used instruments to test and have found that by using an internal pull-up resister, the pin signal level doesnt drop enough.

.

Can you post a picture of this?