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    BME688 -- Bad Gas Resist Results

    BME688 -- Bad Gas Resist Results

    New Poster

    I am using 4 BME688 on a board we designed for the ESP32. The sensors are read using SPI.

    My software is based on the Bosch Parallel-mode example -- measuring 10 steps with a wait time of 6 seconds per each step.

    2 of my sensors perform well. The remaining 2 return a fixed Gas-resist value of 5684.8 for ALL of the steps. One of those sensors also returns a bad pressure result.

    I have this similar phenomemnon on several of these boards. I also have boards where all 4 sensors perform well -- so this is not a board-design issue.

    I also had a phenomemnon were a specific sensor seemed to perform well and then in some instances, sporadically (no rule to it), also gave me this same 5684.8 Gas-resist value in one or more steps.

    I couldn't find anything about this in the data sheet.

    Has anybody else seen this phenomenon?

    Can anyone provide an explanation -- or suggestion what can be done to fix this?

    I attach a sample measurement of the 4 sensors, labeled BME0 - BME3:

    First 2 sensors are good:

            BME:0,ADP:4:    Step:0  Target-Temp:75 for:6[secs]    Measured Temp:30.0 Pressure:1006.3 Humidity:50.2 GasResist:1718120.8 Stat:b0 Idx:0
            BME:0,ADP:4:    Step:1  Target-Temp:200 for:6[secs]   Measured Temp:31.1 Pressure:1006.3 Humidity:47.9 GasResist:100549.9 Stat:b0 Idx:1
            BME:0,ADP:4:    Step:2  Target-Temp:100 for:6[secs]   Measured Temp:30.1 Pressure:1006.3 Humidity:48.1 GasResist:645039.4 Stat:b0 Idx:2
            BME:0,ADP:4:    Step:3  Target-Temp:225 for:6[secs]   Measured Temp:30.9 Pressure:1006.3 Humidity:47.5 GasResist:76646.7 Stat:b0 Idx:3
            BME:0,ADP:4:    Step:4  Target-Temp:125 for:6[secs]   Measured Temp:30.1 Pressure:1006.3 Humidity:48.1 GasResist:364932.3 Stat:b0 Idx:4
            BME:0,ADP:4:    Step:5  Target-Temp:275 for:6[secs]   Measured Temp:30.9 Pressure:1006.3 Humidity:47.6 GasResist:88581.3 Stat:b0 Idx:5
            BME:0,ADP:4:    Step:6  Target-Temp:150 for:6[secs]   Measured Temp:30.1 Pressure:1006.3 Humidity:48.3 GasResist:458678.6 Stat:b0 Idx:6
            BME:0,ADP:4:    Step:7  Target-Temp:325 for:6[secs]   Measured Temp:30.9 Pressure:1006.3 Humidity:47.8 GasResist:141241.4 Stat:b0 Idx:7
            BME:0,ADP:4:    Step:8  Target-Temp:175 for:6[secs]   Measured Temp:30.2 Pressure:1006.3 Humidity:48.1 GasResist:558494.7 Stat:b0 Idx:8
            BME:0,ADP:4:    Step:9  Target-Temp:375 for:6[secs]   Measured Temp:31.0 Pressure:1006.3 Humidity:47.6 GasResist:175703.5 Stat:b0 Idx:9

            BME:1,ADP:4:    Step:0  Target-Temp:75 for:6[secs]    Measured Temp:29.0 Pressure:1006.3 Humidity:52.7 GasResist:2684141.5 Stat:b0 Idx:0
            BME:1,ADP:4:    Step:1  Target-Temp:200 for:6[secs]   Measured Temp:30.2 Pressure:1006.3 Humidity:49.9 GasResist:103664.7 Stat:b0 Idx:1
            BME:1,ADP:4:    Step:2  Target-Temp:100 for:6[secs]   Measured Temp:29.4 Pressure:1006.4 Humidity:49.6 GasResist:769057.4 Stat:b0 Idx:2
            BME:1,ADP:4:    Step:3  Target-Temp:225 for:6[secs]   Measured Temp:30.4 Pressure:1006.3 Humidity:48.7 GasResist:98918.1 Stat:b0 Idx:3
            BME:1,ADP:4:    Step:4  Target-Temp:125 for:6[secs]   Measured Temp:29.7 Pressure:1006.3 Humidity:48.7 GasResist:601291.8 Stat:b0 Idx:4
            BME:1,ADP:4:    Step:5  Target-Temp:275 for:6[secs]   Measured Temp:30.7 Pressure:1006.4 Humidity:48.0 GasResist:123195.4 Stat:b0 Idx:5
            BME:1,ADP:4:    Step:6  Target-Temp:150 for:6[secs]   Measured Temp:30.0 Pressure:1006.3 Humidity:48.1 GasResist:762614.1 Stat:b0 Idx:6
            BME:1,ADP:4:    Step:7  Target-Temp:325 for:6[secs]   Measured Temp:30.9 Pressure:1006.4 Humidity:47.4 GasResist:192048.0 Stat:b0 Idx:7
            BME:1,ADP:4:    Step:8  Target-Temp:175 for:6[secs]   Measured Temp:30.3 Pressure:1006.3 Humidity:47.5 GasResist:879536.2 Stat:b0 Idx:8
            BME:1,ADP:4:    Step:9  Target-Temp:375 for:6[secs]   Measured Temp:31.1 Pressure:1006.4 Humidity:46.9 GasResist:191832.1 Stat:b0 Idx:9
    Here Pressure value is bad and Gas is fixed at 5684.8 -- sometimes the stat is 0xa0 and sometimes 0xb0
            BME:2,ADP:4:    Step:0  Target-Temp:75 for:6[secs]    Measured Temp:29.9 Pressure:689.6 Humidity:51.1 GasResist:5684.8 Stat:b0 Idx:0
            BME:2,ADP:4:    Step:1  Target-Temp:200 for:6[secs]   Measured Temp:31.2 Pressure:690.9 Humidity:47.4 GasResist:5684.8 Stat:a0 Idx:1
            BME:2,ADP:4:    Step:2  Target-Temp:100 for:6[secs]   Measured Temp:30.4 Pressure:690.1 Humidity:46.6 GasResist:5684.8 Stat:b0 Idx:2
            BME:2,ADP:4:    Step:3  Target-Temp:225 for:6[secs]   Measured Temp:31.5 Pressure:691.3 Humidity:45.5 GasResist:5684.8 Stat:a0 Idx:3
            BME:2,ADP:4:    Step:4  Target-Temp:125 for:6[secs]   Measured Temp:30.9 Pressure:690.6 Humidity:45.3 GasResist:5684.8 Stat:b0 Idx:4
            BME:2,ADP:4:    Step:5  Target-Temp:275 for:6[secs]   Measured Temp:31.9 Pressure:691.7 Humidity:44.4 GasResist:5684.8 Stat:a0 Idx:5
            BME:2,ADP:4:    Step:6  Target-Temp:150 for:6[secs]   Measured Temp:31.3 Pressure:691.1 Humidity:44.3 GasResist:5684.8 Stat:b0 Idx:6
            BME:2,ADP:4:    Step:7  Target-Temp:325 for:6[secs]   Measured Temp:32.3 Pressure:692.1 Humidity:43.6 GasResist:5684.8 Stat:a0 Idx:7
            BME:2,ADP:4:    Step:8  Target-Temp:175 for:6[secs]   Measured Temp:31.6 Pressure:691.4 Humidity:43.5 GasResist:5684.8 Stat:b0 Idx:8
            BME:2,ADP:4:    Step:9  Target-Temp:375 for:6[secs]   Measured Temp:32.6 Pressure:692.5 Humidity:42.9 GasResist:5684.8 Stat:a0 Idx:9
    Here Pressure is good but Gas is fixed at 5684.8
            BME:3,ADP:4:    Step:0  Target-Temp:75 for:6[secs]    Measured Temp:30.0 Pressure:1006.3 Humidity:53.0 GasResist:5684.8 Stat:b0 Idx:0
            BME:3,ADP:4:    Step:1  Target-Temp:200 for:6[secs]   Measured Temp:31.4 Pressure:1006.3 Humidity:49.7 GasResist:5684.8 Stat:b0 Idx:1
            BME:3,ADP:4:    Step:2  Target-Temp:100 for:6[secs]   Measured Temp:30.7 Pressure:1006.3 Humidity:48.9 GasResist:5684.8 Stat:b0 Idx:2
            BME:3,ADP:4:    Step:3  Target-Temp:225 for:6[secs]   Measured Temp:31.8 Pressure:1006.3 Humidity:47.2 GasResist:5684.8 Stat:b0 Idx:3
            BME:3,ADP:4:    Step:4  Target-Temp:125 for:6[secs]   Measured Temp:31.0 Pressure:1006.3 Humidity:46.7 GasResist:5684.8 Stat:b0 Idx:4
            BME:3,ADP:4:    Step:5  Target-Temp:275 for:6[secs]   Measured Temp:32.0 Pressure:1006.3 Humidity:45.3 GasResist:5684.8 Stat:b0 Idx:5
            BME:3,ADP:4:    Step:6  Target-Temp:150 for:6[secs]   Measured Temp:31.3 Pressure:1006.3 Humidity:45.1 GasResist:5684.8 Stat:b0 Idx:6
            BME:3,ADP:4:    Step:7  Target-Temp:325 for:6[secs]   Measured Temp:32.3 Pressure:1006.3 Humidity:44.4 GasResist:5684.8 Stat:b0 Idx:7
            BME:3,ADP:4:    Step:8  Target-Temp:175 for:6[secs]   Measured Temp:31.5 Pressure:1006.3 Humidity:44.2 GasResist:5684.8 Stat:b0 Idx:8
            BME:3,ADP:4:    Step:9  Target-Temp:375 for:6[secs]   Measured Temp:32.4 Pressure:1006.3 Humidity:43.3 GasResist:5684.8 Stat:b0 Idx:9
    3 REPLIES 3

    Community Moderator
    Community Moderator

    Hi amitr,

    You can run the force mode example first to access a single sensor, such as "BME: 2" or "BME: 3". If the pressure and resistance values are normal, then the hardware is OK, and you need to check the software code.

    Occasional Visitor

    Hi, I got the same problem with the board which set up BME688 and ENS160.

    Do you have the solution for it??

    Thank you so much

    Community Moderator
    Community Moderator

    Hi kira,

    Could you give detailed log information for check and what is your software code like?