Windsensor

This wind sensor consists of the following hardware components:

• Davis Vantage Pro 2 anemometer and direction vane
• ESP32 Microcontroller
• Waveshare SIM800C GSM/GPRS HAT
• Mean Well RS-25-5 AC/DC power supply, 5A 25W 5V/DC
• optional: Finder print relay 30.22.7 5V

The sensor evaluates the wind speed (pulses of the anemometer) and direction (heading of the vane) every second and stored them for later delivery. Every minute, the collected data get sent to a service on the internet.

Schematic

Output message format

The collected wind data get sent to a service every minute in messages like the following one:

{
	"version":"2.0.0",
	"sequenceId":60,
	"messages":[
		{
			"anemometerPulses":[0,1,4,2,1],
			"directionVaneValues":[32,38,35,38,39],
			"secondsSincePreviousMessage":0
		},
		{
			"anemometerPulses":[6,7,6,5],
			"directionVaneValues":[800,920,880,1200],
			"secondsSincePreviousMessage":62
		}
	],
	"errors":["GSM_MODULE_DID_NOT_REGISTER","HTTP_RESPONSE_CODE_404"]
}

Envelope format

This section describes the properties of the envelope.

property	type	range	description
version	string	"2.0.0"	The message format version
sequenceId	integer	0 <= id <= 999	This property gets used to identify duplicates and out of order received messages. It gets incremented for each new message and wraps around ( ..., 998, 999, 0, 1, ...).
messages	array of message objects		Each message object (see message format description) in the array contains the measured values of a measurement cycle. Typically this array contains only one message. More than one message can be added to deliver those that failed to delivered in the past (e.g. because of network issues). In such a case the first message in the array is the oldest and the last message is the newest.
errors	array of strings		Data delivery errors recorded by the sensor. The sensor records the reasons and resets them as soon as delivery succeeded.

Message format

This section describes the properties of a message.

property	type	range	description
anemometerPulses	array of integers	0 <= pulses <= 255	Each value in the array defines the number of anemometer pulses counted within one second
directionVaneValues	array of integers	0 <= direction <= 4095	Each value in the array defines the direction the vane was pointing to. 0 stands for 0° (north), 1024 for 90° (east), 2048 for 190° (south) and 3072 for 270° (west).
secondsSincePreviousMessage	integer	seconds >= 0	The number of seconds passed since the previous message was sent. Set it to 0 when the messages property of the envelope contains only one message. This value enables the receiver of this message to store the message with the corresponding timestamp.

Building and uploading/flashing

To build and upload the software to the ESP32 the following steps are necessary:

1. Connect your ESP32 via USB to your computer.
2. Adapt the paths used in startDevEnvInDocker.sh.
3. Start the ESP32 development environment executing startDevEnvInDocker.sh.
4. Call idf.py menuconfig.
5. Navigate to "Component config > windsensor > URL of the service" and set the URL.
6. Navigate tp "Component config > Log output > Default log verbosity" and set it to "Info".
7. Save the configuration.
8. Call idf.py flash.

Separate building and uploading/flashing

In some virtual environments it is difficult to pass through the USB port from the host to the guest system. In such situations an alternative is to follow the instruction in the previous section and instead of calling idf.py flash use idf.py build. At the end of the build process you'll get a message like the following:

Project build complete. To flash, run this command:
/root/.espressif/python_env/idf4.2_py3.6_env/bin/python ../esp-idf/components/esptool_py/esptool/esptool.py -p (PORT) -b 460800 --before default_reset --after hard_reset --chip esp32  write_flash --flash_mode dio --flash_size detect --flash_freq 40m 0x1000 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0x10000 build/esp32windsensor.bin
or run 'idf.py -p (PORT) flash'

The important part is 0x1000 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0x10000 build/esp32windsensor.bin, which specifies where the bootloader, partition table and application code needs to get copied to. You can use the Flash Download Tool for Windows to transfer the bin-files to the ESP32.

References

windsensor-service

ESP32 (getting started)

ESP32 (build system)

Flash Download Tool for Windows