nRF52840 I2C timing spec.

[Poki Huang]

Hi 

About nRF52840 I2C data read (CLK rate 400KHz)

1. Could you help check below three I2C items(tHD;DAT, tHD;STA, tSU;STO) can follow I2C standard(NXP) spec. or need follow nRF52840 spec.?

Since our measurement can pass standard but fail nRF52840

2. About data fall time(tf), nRF52840 datasheet no define this item, and I2C standard define min. value is 20*(VDD/5.5V), and our measurement fail I2C standard

But I check some other device, they didn’t define min. value, so could you help check if nRF52840 can accept min. value=0 ?

Thank you~~

Poki

[Poki Huang]

Hi Vidar:

I want to let you know again that we are discussing nRF52840 I2C SDA read data spec., not I2C SDA send data to device spec.

1. So you mean about these three I2C items(tHD;DAT, tHD;STA, tSU;STO) that nRF52840 datasheet list spec. is to promise that nRF52840 send data can meet those spec. right?

So for nRF52840 read data spec. we can follow I2C standard(NXP) spec., so our below measurement result is pass right?

 

2. For data fall time(tf), the I2C standard spec. need > 20*(VDD/5.5V) , so for our case VDD=2.1V, the spec. need > 7.63ns

But this data fall time(tf) spec. didn't list at your nRF52840 datasheet, that mean you don't concern this timing right?

If yes, so below our measurement 0.3899 is ok for nRF52840 right?

Thank you~~

Poki

[Vidar Berg]

Hi Poki,

1. Yes, that is what I meant. So the measured timings look good as far as I can tell.

2. Yes, I would not expect this to be a problem for the nR52. But I misread your measured value earlier, I read it without the decimal point so I thought you were above max. and not below Min. So rather than increasing the drive strength as I suggested, you should use the standard drive.

Best regards,

Vidar