Falling time of I2C of BHI160 and BMM150

[Randomwufan]

Hi Bosch,

We are using BHI160 and BMM150 in our product. There is a I2C Bus between them, which is pin7/21 of BHI160.

I measured the waveform of this I2C and found falling time is too short (8.7ns on SDA;6.2ns on SCL). The I2C standard (UM10204) defines the minimum falling time should be 12ns.

My question is will it cause a problem? Does BHI160 have register to control the driven strength?

Thanks!

[Vincent · Accepted solution]

When using BHI160 + BMM150 combination, the I2C host are working under 400Hz,  and in the spec there is only max falling time defined under 400Hz.

And this timing is working properly with BMM150 on BHI160 I2C host interface

[Randomwufan]

Hi Vincent,

I2C works at 400Khz, not 400Hz from my test. Are you sure it is 400Hz? Please check the waveform I measured as below. Yellow is clock while Pink is data.

Thanks!

cheers

Fan

[o_o]

Hi Fan,

Indeed this looks a bit faster than the i2c spec. I need to confirm if this is expected or not.

For the BMM150 interface, this will not cause an issue. BHI160 does not have configurable pad strenght.