TWI and 28/29 pin issue

[Legath]

I am try to make twi communication and i got strange issue.

When i use twi scanner example with unconnected pins on my board , i am not see any requests

Great oddity that pin 29 (sda) in low always.

 const nrf_drv_twi_config_t twi_config = {
       .scl                = 28,
       .sda                = 29,
       .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };

If i change pins to 30 and 31 , all work as i expect.

I did not seen any additional descriptions about 28-29 pins and twi.

Where is my mistake about these pins and twi?

Also, this is my board scheme

[Kenneth]

It is common to place pull-up resistors (example 10kohm) on the TWI pins (SDA and SCL). Have you done so? Else I recommend to check if you may have anything else in your code that may be using pins 28 or 29. Or can it be a short somewhere?

Best regards,
Kenneth

[Legath]

Module have Pull-up. As i say , it work on other pins, I have checked reuse pins , and nothing. I disabled buttons and leds, and all other tasks. Even twi_scanner example does not work on this pins.

So, do you think that is hw issue? not software limitation?

[Kenneth]

All pins can be configured to use TWI, there is no hardware limitation.

Best regards,
Kenneth