A few questions regarding data logging over WiFi to Android (from ESP8266)

Good morning from Oregon, USA!

I am new to the forums but thankful for the great resource it has been. I have just started playing with Arduino and it is amazing what I have been able to do.

I have a question regarding interfacing my mini Node MCU, using the ESP8266, with an Android device over WiFi. Specifically I want to be able to send logged voltage values OTA to my android phone for logging. My phone shows the board as a network access point, but how can I get the board to send me the data values in something like an ASCii table? I would like to be able to record these timestamped voltage values in the field and store them to my phone's onboard SD card. I currently use a serial monitor on my computer for data logging and, while this is great, need a more wireless solution. I chose WiFi for it's superior range and packet handling, but would BLE be the better option here?

Thanks for reading my questions.

you can collect the data in the esp8266 flash and download it later over web interface

This guide has a temperature logging example.

Right well.

I see various options here...

  1. The ESP8266 sends data to webhost you have (locally hosted or even a cheap webhost)...you can then access the website on your phone. You'll need some PHP and SQL coding knowledge or seek it out.

  2. The ESP is connected to via your phone...directly. The ESP can act as an Access Point and host a small "website".
    On connect, your phone could ask for the data...then on receipt of the data, parse it in to say a CSV (append it to). This avoids
    any remote web server, but you'd need to know Android/Java or Swift. Also you can only get the data when you are within the
    wifi range of the phone/ESP8266.

  3. Bluetooth is lower range but quite simple in terms of integration in to an Android/Swift app. It has the same pitfalls as in option
    2...but is just a different communications system.

These are great suggestions, thank you Wawa for that manual; this seems like an easy interm solution while I wrap my head around interfacing with Android.

Johnny010, option #2 is what I'm looking for. Know of any such templates for apps that can create csv files like you mention? Not familiar with Java at all, but I'm sure I can learn enough to design something simple.

Another sort of unrelated question: is there code for having the arduino output a timestamped voltage value? Right now I've been just copying the voltage values into a spreadsheet, assigning a second column as a time axis and constructing graphs that way. However, I'd much rather have a timestamp straight from the device.

Thanks for all the help.

The link I gave you saves timestamped csv values to the SPIFF (flash) memory of the ESP.
Timestamps are derived from an internet time server (like your computer does).
I suppose it's not that hard to replace the DS18B20 temp sensor part with voltage measurement code.

I would build/use the code in it's current form (with DS18B20), and learn from it.
Then convert (or add) the voltage measurement part.