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TROUBLESHOOTING.md

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Troubleshooting

This file lists solutions for some common problems. Please check it before opening a GitHub issue.

Contents

Standard checks
RuntimeError: Failed to add edge detection
WiFi Access Point examples not starting
ESP8266 problems
ESP32 problems
Arduino Nano 33 IoT problems
WiFi connection problems
Particle sensor problems
Slow air quality accuracy change
Temperature measurement is too high

Standard checks

Most problems can be resolved by following these steps:

  1. Check that you can run a simple program on your host system without the MS430 board e.g. blink and serial demos on Arduino.
  2. Ensure you have the most recent sensor code and instructions from our GitHub repository
  3. Check your software, library and board versions: for best reliability, use the versions listed in the Readme.
  4. Remove all wire connections and re-wire carefully.
  5. If you have edited the code, go back to the original version and ensure it still works.

Edge detection error

The Python examples running on Raspberry Pi may cause a Failed to add edge detection runtime error. This happens in the "Bookworm" version of Raspberry Pi OS, due to a problem with the old GPIO library. It may also occur in future OS versions. The simple fix is to install the new improved GPIO library by running the following:

sudo apt remove python3-rpi.gpio
sudo apt update
sudo apt install python3-rpi-lgpio

WiFi Access Point examples not starting

  • The Arduino web server examples, when the host is configured to be a WiFi Access Point, may fail to start immediately after programming the board. This seems to affect ESP8266 and Raspberry Pi Pico W, and is presumably due to the host board failing to reset after programming.
  • Solution: simply power-cycle the host board (unplug and re-plug power).

ESP8266 problems

There are many different development boards which use the ESP8266 module. Some may have different pin labels, or have different pin positions, so you may need to research your board or (rarely) edit the host_pin_definitions.h file.

The ESP8266 does not have a hardware I2C module, so any of the normal GPIO pins can be used for the I2C bus.

ESP32 problems

There are many different development boards which use the ESP32 module. Some may have different pin labels, or have different pin positions, so you may need to research your board or (rarely) edit the host_pin_definitions.h file.

After uploading a new program, the serial monitor may show a stream of nonsense characters instead of starting the program. Try pressing the board's EN/RESET button.

Arduino Nano 33 IoT problems

The GitHub code releases before v3.1.0 used a software I2C library for the Nano 33 IoT. The code now uses the hardware I2C module, with different pins - please follow the readme file to re-wire your setup.

WiFi connection problems

If WiFi connection never succeeds, check the following:

  • SSID and password are correct
  • The WiFi access point is functioning and within range
  • WiFi library, Arduino board package, and board firmware versions are up-to-date and compatible
  • Power supply is sufficient
  • Arduino WiFi antenna is not damaged (very easy to damage on the Arduino Nano 33 IoT)

Particle sensor problems

Measured value does not change

  • Check wiring
  • Check the input voltage - the "5V" must be 4.7-5.3 V
  • If using a separate 5V source, the source GND must be connected to both the host GND and the MS430 GND.

Measured value fluctuates a lot

  • This is typical for particle sensors, especially the PPD42
  • Check the input voltage - the "5V" must be 4.7-5.3 V
  • Using a separate, regulated 5V supply can reduce the fluctuation.

Slow air quality accuracy change

The air quality measurement accuracy can be slow to increase, especially with new sensors, for two reasons:

  1. The air quality sensor uses a small internal heater - this will gradually evaporate off impurities when used after a period of storage.

  2. The analysis algorithm self-calibrates in response to a range of air qualities, which must be provided to the sensor after it starts monitoring.

To speed up this process:

  • Run any code example which repeatedly measures the air quality, with 3 second cycle selected (e.g. cycle_readout, web_server, log_data_to_file)
  • Keep it running as long as possible, ideally at least 48 hours
  • If the accuracy is low (0 or 1) after running for an hour, expose the sensor to polluted air for a few minutes. A solvent vapor such as from a marker pen or alcohol is ideal.

In normal use the accuracy does not remain on 3 (highest) all the time but instead will periodically decrease/increase as calibration is ongoing.

Temperature measurement is too high

  • The temperature sensor measurement may have a small offset compared to the true temperature.

  • The offset is different for each sensor but should remain mostly constant, so you can subtract it in your software after comparing with an accurate thermometer.

  • A larger offset will result if you put the sensor board in a case, especially if together with the host system. Hosts (and particle sensors) create heat, so should be separated or insulated from the sensor board.

Support

If the information here does not help, please open a GitHub issue.