Problem with UART reading (MH-Z19B sensor)

[fdufnews]

Is this garbage only occuring during the first exchange or for every other ones?

If it is only on the first one, it is surely a problem linked to the setup of the sensor. In that case, maybe you can add a few seconds delay before entering the flush loop I suggested. The delay shall be longer than the time it takes for the sensor to make its internal calibration and end its setup.

[KUMO]

Is this garbage only occuring during the first exchange or for every other ones?

If it is only on the first one, it is surely a problem linked to the setup of the sensor. In that case, maybe you can add a few seconds delay before entering the flush loop I suggested. The delay shall be longer than the time it takes for the sensor to make its internal calibration and end its setup.

The garbage comes with each reading no matter how long I waited. Really strange.

[Roberthh]

If I look at your screen copies, the garbage comes at the first read, causing an offset of 3 bytes. That offset continues through the following reads of 9 bytes each and results in bad results. Again: every time before sending out a command to the sensor you have to ensure that nothing is already in the receive buffer.

[KUMO]

If I look at your screen copies, the garbage comes at the first read, causing an offset of 3 bytes. That offset continues through the following reads of 9 bytes each and results in bad results. Again: every time before sending out a command to the sensor you have to ensure that nothing is already in the receive buffer.

Thanks again for your advice, Robert!
I connected the sensor now to Arduino. Quite interesting, there is no such problem, the reading for the first two minutes shows zero, after correct value was displayed.