airgradient/docs/local-storage-experimental.md

This document to explain local storage mode - experimental

How it works?

1. Monitor directly goes to local storage mode
2. On boot, monitor will attempt to connect to default wifi. And if connected, mdns and local server will be enabled, otherwise it will ignore and continues the measurements
3. On display, when boot it will show the mode ("local storage mode") and wifi related scenario. After that, monitor will show the measurements dashboard
4. Measurement records to the local storage every two minutes that saved on CSV file in SPIFFs partition
5. Every successful writes, monitor will blink the most left led bar to blue twice, but if failed it will blink red twice. There are two possibilities for failed write, SPIFFs partition already full or out of heap memory when load the file.
6. There are 2 endpoinds added for this mode, download measurements from local storage and reset measurement (delete old measurements file and create new one) with new timestamp. Timestamp here to set the monitor system time.

Notes

1. Default wifi
   • ssid ➝ airgradient
   • password ➝ cleanair
2. Maximum measurements file is around 113kb. If assume each measurements is 60 bytes, with write schedule 2 minutes, SPIFFS will be full in around 5 days
3. WiFi connection attempt on boot wait for 10s before considering timeout
4. Tips. If monitor not connected to wifi on boot, no need to restart the monitor for reconnection, it will automatically connect to AP once it is available

Local Storage Endpoinds

Make sure monitor is connected to AP, and client also connect to it. And change the serial number on the url

Download measurements file

To download measurements file from local storage, just directly access following url on the browser http://airgradient_aaaaaaaa.local/storage, and browser should automatically download the file.

Reset measurements

Execute below command in terminal

curl -X PUT -H "Content-Type: text/plain" -d '1733431986' http://airgradient_aaaaaaa.local/storage/reset

1733431986 this data is the time that we want to set monitor system time to. Its in epoch time format and expecting UTC+0 timezone.

To get epoch time, access this url https://www.unixtimestamp.com/, and click copy button.

Example measurements file content

datetime,pm0.3 count,pm1,pm2.5,pm10,temp,rhum,co2,tvoc,nox
05/12 21:10:59,869.67,11.17,20.33,21.83,26.69,72.93,417,40,1
05/12 21:11:30,834.83,11.50,19.33,20.33,26.68,73.08,413,79,1
05/12 21:12:01,829.67,10.33,19.33,22.00,26.64,73.09,412,90,1
05/12 21:12:32,831.50,10.33,18.33,20.83,26.62,73.21,411,97,1
05/12 21:13:02,887.50,12.00,20.33,21.67,26.59,73.33,412,95,1
05/12 21:13:33,785.17,8.67,18.50,19.50,26.56,73.43,414,92,1
05/12 21:14:04,827.50,10.50,18.50,19.50,26.54,73.43,415,98,1
05/12 21:14:35,815.83,10.50,19.50,19.83,26.49,73.47,413,99,1