I2C CURRENT LEAK

[KentOverton]

Hi,

I have a current leak on a new board.

I'm using a nrf52840.

My development environment is nRF Connect SDK v2.6.0.

I am using power management on I2C1.

When I initialize i2c1 i run 

   err = pm_device_action_run(i2c1, PM_DEVICE_ACTION_SUSPEND);                  // after opening and configuring the i2c device, suspend it

I've checked and err is 0 after the SUSPEND

I2c1 is defined in app.overlay as 

&i2c1 {
status = "okay";
pinctrl-0 = <&i2c1_default>;
pinctrl-1 = <&i2c1_sleep>;
pinctrl-names = "default", "sleep";
};

&pinctrl {

i2c1_default: i2c1_default {
group1 {
psels = <NRF_PSEL(TWIM_SDA, 0, 34)>,
<NRF_PSEL(TWIM_SCL, 0, 37)>;
//bias-pull-up;
};
};

i2c1_sleep: i2c1_sleep {
group1 {
psels = <NRF_PSEL(TWIM_SDA, 0, 34)>,
<NRF_PSEL(TWIM_SCL, 0, 37)>;
//low-power-enable;
};
};

In this state - (i2c initialized and suspended) I see around 100 mV on the SDA and SCL lines.

I expected to see no voltage there at all.

Am I incorrect?

};

[Turbo J]

Idle state on the I²C lines is HIGH, i.e. being pulled up by the bus resistors. Why do you expect a low voltage here?

[KentOverton]

I had expected the suspend to fully idle the I2C signals - including removing the pull ups.

[Håkon Alseth]

Hi,

 

When using GPIO Port P1, you should describe it a bit different:

i2c1_default: i2c1_default {
group1 {
psels = <NRF_PSEL(TWIM_SDA, 1, 2)>,
<NRF_PSEL(TWIM_SCL, 1, 5)>;
//bias-pull-up;
};
};

 

In this state - (i2c initialized and suspended) I see around 100 mV on the SDA and SCL lines.

I expected to see no voltage there at all.

In this state the IOs will be floating, as there's no pull applied internally nor externally.

 

Kind regards,

Håkon

[KentOverton]

Håkon,

I solved it in a diffefrent way

I added bias_pull_up and bias_pull_down statemts to the i2c pinctrl statements. They are now

    i2c1_default: i2c1_default {

        group1 {

            psels = <NRF_PSEL(TWIM_SDA, 0, 34)>,

                <NRF_PSEL(TWIM_SCL, 0,  37)>;

            bias-pull-up;

        };

    };

    i2c1_sleep: i2c1_sleep {

        group1 {

            psels = <NRF_PSEL(TWIM_SDA, 0, 34)>,

                <NRF_PSEL(TWIM_SCL, 0, 37)>;

                bias-pull-down;

        };

When the i2c1 port is suspended SDA and SCL are quite low - less than a milli-VOLT.

When the i2c1 port is acrive SDA and SCL are at 3.3 Volts.