Closed stolk closed 2 years ago
Hi @stolk
Thank you for reaching out to us. Did you consider the details mentioned in the datasheet regarding single shot measurements?
Here's the section from https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9.5_CO2/Sensirion_CO2_Sensors_SCD4x_Datasheet.pdf The relevant part is marked in bold, but please read the whole thing.
3.10 Low power single shot (SCD41) In addition to periodic measurement modes, the SCD41 features a single shot measurement mode, i.e. allows for on-demand measurements. The typical communication sequence is as follows:
I suspect an unstable power supply has caused this issue.
I have moved to automatic sample mode, and a different microcontroller, and the measurement values are more stable now.
I am getting highly suspect values from single shot measurements. As low as 217 ppm, with wild swings to 700, indoors. I don't think they are correct.
I feed ambient pressure (991 currently, in my location) and wait for the data ready signal.
But I am getting nonsense back.
Is my sensor broken? Is single-shot function broken?
In the main loop:
Note: for some single shot measurements, the data rdy signal is never shown.