I2C SCL no clock

[VThan.2]

Hello,

I am trying to get my I2C code Master working. I don't have the slave device connected and I am trying to see the output on a logic analyzer. I have connected the SCL and SDA pins to breadboard to a 2k pull up of 3.3V and the board is running at 3.3V. For some reason I cannot see the SCL toggling. It goes low and it stays low throughout the entire data address transmission period. Typically the scl and sda should have the address data and a NACK as there is no slave, but in this case the SCL is not toggling. Any suggestion how I can fix it? Thank you

 

[TDK]

Show an analog trace. I would guess the pullup is insufficient.

[VThan.2]

Thank you. Do you mean on a scope?

[TDK]

Yes. It looks like you're using a Saleae logic analyzer which can take analog captures as well as digital ones.

[VThan.2]

Yes looks bad

[VThan.2 · Accepted solution]

@TDK​ I tried increasing the resistance to 1K and my analog sampling to 50MS on logic analyzer and I seem to be getting the scl lines. I am not sure why the logic analyzer still does not see it. I still think there might be something to do with my settings on I2C line. Any thoughts?

[VThan.2]

Never mind, got it working the glitch filter was enabled on the logic analyzer. Fixed it. Thank you

[waclawek.jan]

Thanks for coming back with the solution. Please select your post as Best so that thread is marked as solved.

JW