nRF5340-DK operating voltage at 1.8V?

[SteveG128]

Hi,

I'm trying to get my firmware running on a nRF5340-DK before I have my real hardware. I've connected a MAX86171 via I2C to the DK, the MAX86171 has a nominal operating voltage of 1.8V. I've configured the DK to operate off the external supply connector and connected a 1.8V supply to the DK.

The problem is the I2C signals (SDA, SCL, P1.02 and P1.03) don't move at 1.8V. If I remove the MAX86171 and increase the external supply to 3.0V, the I2C signals appear signal properly.

My questions:

1. Can I run the nRF5340-DK at 1.8V and expect the I2C and another GPIO acting as an interrupt input to be fully functional?

2. Should I expect a uBlox NORA-B1 series BLE module to operate properly at 1.8V? The data sheet states an operating voltage of 1.7V to 3.6V

Regards

Steve

[SteveG128]

Jared,

I'm using a bench supply and the current limit is well above any expected current requirements of the DK.

I'm using connector P1 pin 1 of the DK for the MAX86171 1.8V

More importantly, if I remove the MAX86171 and simply watch SCL and SDA with the scope, there is no activity on the signals until I supply 3V (it may be a lower voltage, I just tested 1.8V and 3V). My shield board pulls up both signals with 4K7 resistors to the DK's Vdd.

Steve 

[Jared]

Hi Steve,

Which version of NCS are you using?

SteveG128 said:

More importantly, if I remove the MAX86171 and simply watch SCL and SDA with the scope, there is no activity on the signals until I supply 3V (it may be a lower voltage, I just tested 1.8V and 3V)

Could you share a minimal sample that would reproduce this, so I could recreate this on my DK?

regards
Jared 

[SteveG128]

Hi Jared,

I'm using Version 2.1.0.

I can duplicate the issue using the sample ncs\v2.1.0\zephyr\samples\drivers\i2c_fujitsu_fram

It doesn't matter if there is a I2C device, just the pull-ups on SCL and SDA are required.

Steve

[Jared]

Steve,

I tried to reproduce this with the i2c_fujitsu_fram sample but wasn't able to. I connected a power supply to the P21 external supply connector and saw that there indeed was activity on both SCL and SDA when I lowered the voltage. At 1V8 I would see several resets which I think is brown-out resets but it became stable when I increased it to about 1V9. I did not use external pull ups, instead I modified the dts to activate the internal pullups with pin ctrl like this:

 

[SteveG128]

Jared,

The lowest voltage my DK will activate the I2C bus at is 2.45 volts. The DK runs code at 1.8V, no resets are occurring but the GPIOs are non-functional. I going to assume that my DK is bad, but I'm not going to buy another on the hope that it would work.

My hardware's arrival is imminent so I'll wait for that rather than wasting any more time with the DK. I will update this conversation when and if my HW is working. Most likely next week.

Steve

[Jared]

Hi.

alright, keep me updated.

regards

Jared

[SteveG128]

Jared,

You can close this, my hardware works fine @ 1.8V. The DK does not so it's gone to the recycle bin.

Thanks

Steve