Hi, thank you for using our product. I see a few issues from your description and the developer documentation, I hope you can troubleshoot from there and if it is determined to be a problem with the sensor, we will take care of it for you.
1、This sensor needs to be connected to the pin with ADC function, do you have Arduino on hand, can you change the platform and try again?
2、I learned from the developer’s documentation that it takes 20~30 minutes for the sensor to warm up.
3、You said in the description that you adjusted the baud rate, here I suggest you keep the original code 9600 for use.
Developer documentation: Grove_Gas_Sensor_O2/Grove-Gas_Sensor-O2.md at master · SeeedDocument/Grove_Gas_Sensor_O2 · GitHub