I plugged an STEVAL-MKI224V1 board (basic eval board for baro sensor) on a nucleo F411RE. Communication happens through i2c bus.
I added 4.7k pull-up resistors on SCL and SDA.
- SDO to VDD (set i2c address)
- CS to VDD to activate i2s communication
- VDDIO to VDD to nucleo 3.3V
- GND to nucleo GND.
- SDA and SCL to nucleo.
No internal pull ups are used.
As communication was not successfull on first frames, I plugged a scope on SCL and here's what I get:
On the first bytes, the low level is not +/- 0V as it should be.
I tried a 10k pull-up, the result is the same.
I tried with only pull-ups (without eval board), result is ok.
I tried with another eval board for another sensor (Rohm), the result is far better but there's still a "rounded" 0. On this view, I zoomed a bit, code and i2c configuration is the same:
What did I miss?
Pictures of the setup: