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

[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

[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?

[Hkhan7861]

I will post a picture at a later stage thank you.  I am still not able to find this function.  I am not sure you understand my question.  Please refer me to where the start condition is handled.

[Vidar Berg]

Hkhan7861 said:

I am still not able to find this function.  I am not sure you understand my question.  Please refer me to where the start condition is handled.

There is no function for this because it is handled in HW.

[Hkhan7861]

Oh I see okay thank you ! so would I just need to use 

nrf_twim_task_trigger(p_twim, NRF_TWIM_TASK_STARTTX) and the startup condition will be handled?  

Thank you .

 

[Vidar Berg]

The TWIM peripheral must be configured to transmit data before you can trigger the start task. It is easier to just use the driver APIs to start a transaction as it will take care of the configurations for you.