I have already received several reports about DFRobot Gravity SFA40 modules showing consistently elevated HCHO readings, so I want to collect all diagnostic information in one place and understand how widespread the issue is.
This issue is for users whose HCHO readings stay elevated after warmup. If your values are only high during the first minutes after startup, please wait at least 15-30 minutes before reporting.
Current firmware status
The current SFA40 driver follows the standard Sensirion algorithm from the datasheet. At this point I do not see a clear conversion error or a clear deviation from the documentation in the firmware. The manufacturer-specified SFA40 accuracy is ±20 ppb or ±20%.
It is also important to note that during the first up to 10 minutes after startup, readings may be unstable. After warmup, they should settle.
Diagnostic beta firmware
A beta firmware build with the SFA40 diagnostic page is available here:
https://github.com/21cncstudio/project_aura/releases/download/v1.1.4/project_aura_1.1.5-beta-sfa40-debug-47a75c6-dirty_ota_firmware.bin
SHA256: 58e41171e4cf92e583794cbccb1defaac148930768f321dbf141aee0e043ffc8
After flashing the beta firmware, open:
http://<device-ip>/debug/sfa40
The page will show a copyable report with:
- whether the HCHO reading is ready or still warming up;
- the internal SFA40 measurement state;
- basic communication health information;
- the sensor module identifier, if available;
- the temperature and humidity measured near the SFA40;
- the direct HCHO value before it is shown in the UI.
This should help us separate environment/enclosure effects, module batch problems, cable or power issues, and possible firmware/display issues.
How to report
If you see consistently elevated HCHO readings, please comment with:
- The report copied from
http://<device-ip>/debug/sfa40 after 15-30 minutes of operation.
- The stable HCHO value you see after 15-30 minutes.
- What filament/material was used to print the enclosure.
- Whether the enclosure contains glue, tape, foam, sealant, paint, or other recently assembled materials.
- Whether you placed Aura near fresh air / an open window for about 30 minutes, and what changed.
- Whether you ran Aura without the enclosure, and what changed.
- Whether you compared it with another Aura unit or another HCHO meter in the same room.
- Whether the SFA40 cable/wiring was changed or extended.
Please include photos if the sensor mounting, cable, or enclosure materials may be relevant.
With enough reports, we can contact DFRobot/Sensirion with concrete evidence. If the issue is related to a specific module, batch, environment, or integration condition, we should be able to identify the pattern from the diagnostic data.
I have already received several reports about DFRobot Gravity SFA40 modules showing consistently elevated HCHO readings, so I want to collect all diagnostic information in one place and understand how widespread the issue is.
This issue is for users whose HCHO readings stay elevated after warmup. If your values are only high during the first minutes after startup, please wait at least 15-30 minutes before reporting.
Current firmware status
The current SFA40 driver follows the standard Sensirion algorithm from the datasheet. At this point I do not see a clear conversion error or a clear deviation from the documentation in the firmware. The manufacturer-specified SFA40 accuracy is ±20 ppb or ±20%.
It is also important to note that during the first up to 10 minutes after startup, readings may be unstable. After warmup, they should settle.
Diagnostic beta firmware
A beta firmware build with the SFA40 diagnostic page is available here:
https://github.com/21cncstudio/project_aura/releases/download/v1.1.4/project_aura_1.1.5-beta-sfa40-debug-47a75c6-dirty_ota_firmware.bin
SHA256:
58e41171e4cf92e583794cbccb1defaac148930768f321dbf141aee0e043ffc8After flashing the beta firmware, open:
http://<device-ip>/debug/sfa40The page will show a copyable report with:
This should help us separate environment/enclosure effects, module batch problems, cable or power issues, and possible firmware/display issues.
How to report
If you see consistently elevated HCHO readings, please comment with:
http://<device-ip>/debug/sfa40after 15-30 minutes of operation.Please include photos if the sensor mounting, cable, or enclosure materials may be relevant.
With enough reports, we can contact DFRobot/Sensirion with concrete evidence. If the issue is related to a specific module, batch, environment, or integration condition, we should be able to identify the pattern from the diagnostic data.