The Microcontroller boards need to be manually flashed with the NodeMCU firmware in order to run the Lua programs developed by the students.

Luckily we do not need to set up the complex ESP8266 SDK and can instead use the Online builder provided by the NodeMCU devs.

Go to the builder website, enter a valid mail address and select the following modules to include:

• DHT
• file
• GPIO
• MQTT
• net
• node
• PWM
• timer
• UART
• WiFi

Finally hit “Build” and wait for the firmware file to arrive via E-Mail.

In the E-Mail you will receive a link to a float and an integer version of the firmware. We will be using the float version.

Download the firmware and use esptool (which comes pre-installed on the Raspberry Pi images) to upload it to the microcontroller boards:

$ esptool.py --port /dev/ttyUSB0  write_flash 0 nodemcu-master-…-float.bin
esptool.py v2.5.0
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... ESP8266
Chip is ESP8266EX
Features: WiFi
MAC: 12:34:56:78:9A:CD
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Auto-detected Flash size: 4MB
Flash params set to 0x0240
Compressed 430704 bytes to 277188...
Wrote 430704 bytes (277188 compressed) at 0x00000000 in 24.4 seconds (effective 141.2 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting via RTS pin...

Note: Depending on the source of your esptool installation the command name may be esptool.py or esptool.

This flashing has to be performed once per board.

You should run the image creation process each year before the lab takes place to stay on top of security updates.

Even if you do not generate a new image you should at least re-flash the image to the microcontrollers to make sure the students work in a fresh environment.