I2C clock frequency problem

[Manjunath K S]

Hi,

I am using NRF52832 development board , to which i have interfaced LIS3DSH accelerometer sensor(3.3V i2c)

when i  configure it for 1600 sampling rate and all the axis enabled , i am not able to get any data .

could anyone help with this problem.

also the I2c clock frequency, as shown in below image, while i am capturing data when i observe in oscilloscope or logic analyzer , clock frequency is showing 200 all the setting is for 400KHz.

what could be the problem for this or is there any other way i need to follow to set the clock to 400KHz.

help me ASAP...

Thank you

[haakonsh]

"also the I2c clock frequency, as shown in below image, while i am capturing data when i observe in oscilloscope or logic analyzer , clock frequency is showing 200 all the setting is for 400KHz."
That's unlikely, I think you're measuring the clock frequency incorrectly.


Why have you enabled pulldowns on your IO pins?

[Manjunath K S]

actually that's not the part of code , sorry excluding that is the actual code

[awneil]

So take a look at the SES documentation:

https://studio.segger.com/ses_doc_home.htm

https://www.segger.com/downloads/embedded-studio/EmbeddedStudio_Manual

See also, specifically for Nordic:

https://www.youtube.com/watch?v=uP8RYgYGRvI

https://infocenter.nordicsemi.com/topic/ug_gsg_ses/UG/gsg/intro.html

https://infocenter.nordicsemi.com/topic/ug_gsg_ses/UG/gsg/debug.html

[Manjunath K S]

Is this what u said. please  reply asap.

still not able to get the clock.

[awneil]

What do you think?

haakonsh said:

read the TWI/TWIM registers

Are those the TWI or TWIM registers?

Did you watch the video in the link?

At about 5:25 he shows you how to access peripheral registers ...

[Manjunath K S]

with that explanation only i did this and shared,

there was no TWI/TWIM registers it was shown like that.

so i asked is that what he said.

[awneil]

Manjunath K S said:

there was no TWI/TWIM registers

and the video shows you how to reach peripheral registers!

[Manjunath K S]

ok sorry , now i understood , but sill value is updated as u can see in this one.

[haakonsh]

The FREQUENCY register is actually shared between the TWI, TWIM, SPI, and SPIM peripherals, but, they all use different sets of values to represent their settings:

The TWI's FREQUENCY register docs have defined K400 as 0x06680000, whereas the TWIM's FREQUENCY register docs have defined K400 as 0x06400000. 

There's actually a bug in the legacy TWI drivers where it uses 0x06680000 when you use the SPIM peripheral. It's not really critical as you'll just get ~410kHz instead of 400kHz, and slaves are usually okay with a bit higher clock rate than 400kHz. 



The 200kHz clock you see is probably not the sole product of the TWI/M peripheral, I think there's something on your bus that interferes with your signals. 

Are you able to reproduce the issue on the DK, and can you show us a scope of the clock when running on the DK with no devices attached?

[Manjunath K S]

can u explain what exactly i should do now, without any device means

is it generating PWM.

[awneil]

"without any devices" means exactly that - nothing connected to the I2C lines!

Nothing except the pullups, of course!

In that situation, you should see the Master sending the Slave Address.

Because there is no Slave attached, the Master will see that as a NAK - but it will be enough to see the Clock ...

[haakonsh]

Without any TWI slaves attached to the bus.

I want to see the scope of the clock signal.