Embedded Developer

The weather station project has been struggling for part of September with a random exception in my code. The source of the exception was finally identified although the exact cause is still a mystery. As a temporary measure, the component and the associated source code were removed from the project, this allowed the project to continue.

Source of the Exception

In the previous post, Define a Minimum Viable Product and Ship it, I discussed a replacement for the clock module. This module was changed from the DS3234 to the DS3231 freeing up four additional pins (the DS3231 is an I2C peripheral and the DS3234 uses SPI). This change seems to have introduced some instability into the system.

Several days debugging followed after which I was still unable to isolate the problem. The interim solution is to remove the module and use the Ticker class to trigger an interrupt. Not ideal but this will allow the rest of the software to be soak tested.

The additional Ticker object fires once per minute to trigger the reading of the sensors. In addition, the interrupt will check the current time and if the hour and minute are both zero then the application will reset the pluviometer counter.

Soak Testing

As mentioned above, one Ticker object is generating an interrupt once per minute. The frequency of the interrupt is higher than will be used in the final project. One minute is more than enough time to perform the sensor readings and log this to the internet but also frequent enough to simulate a prolonged period in the field.

The prototype board was also located close to the final home for the sensors. This hit a problem as the range of the WiFi network was not sufficient for the ESP8266. This problem has prevented the prototype to be tested in the field at the moment.

Conclusion

The prototype board is currently sited on a window ledge in the house. taking temperature, humidity and luminosity readings once per minute. This data is logged to the Sparkfun Phant Data Service. The system has been running continuously for the last 7 days (approximately 10,000 readings).

The software seems stable at the moment, the next problem, extend the range of the WiFi network.

Tags: Electronics, ESP8266, Software Development