Internet access

Once we have collected data from the sensors we want to get access to them. This can be accomplished most easily by transferring the data over the Internet. Most of the time we also want to plot the data in some form or another. Often it is also desired to see real time data.

WiFi

Before doing anything on the Internet we must first connect the ESP32 to the WiFi network. The module:

https://iotworkshop.africa/pub/IoT_Course_English/InternetAccess/wifi_connect_public.py.txt

provides all necessary functions to do this. It first connects to WiFi as a station interface and print the IP address it is connected to. If it is already connected it simply returns. Once connected it gets the current time from the NTP time server and sets up the ESP32 real time clock. You can get the current GMT time with gmtTime() or CET time with cetTime(). The module is already included in the MicroPython binary.

You can also get the current date and time in a more readable format with dateString(currentTime), where currentTime is the tuple returned by gmtTime() or cetTime()

Since I cannot know the SSID and password of your WiFi network, connect() will only work for my private network. You can however pass your SSID and password as parameters:
connect(ssid="YourSSID",password="YourWiFiPasswword")

You can get the IP address allocate with

getIPAddress().

An FTP server

When collecting data it may be interesting to transfer them for analysis to a PC. For this an FTP server is very helpful and there is one included in the MicroPython binary. Make sure you are connected to the network with wifi_connect and then simply
import uftpd. You may stop the server again with uftpd.stop().

More information about the ftp server can be found at https://github.com/robert-hh/FTP-Server-for-ESP8266-ESP32-and-PYBD

Exercises for the Internet part of the IoT course

In this course we will have a look into two ways of accessing our data:

• a WEB server implemented on the ESP32
• transfer of the data through MQTT to a Cayenne server offering display and logging of our data.

Uli Raich - 2020-04-28

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