WisBlock Kit 1 Weather Station is a project that uses a RAK4631 LoRa module in order to transmit data (Temperature, Pressure, Luminosity and Humidity) over an Helium Gateway (RAK Miner V2) that relays data to an Helium router that dispatches the data to the platforms MyDevices Cayenne and Ubidots.
- RAK4631 Weather Monitoring - WisBlock Kit 1
Before going further, I would suggest you to read the official RAK4631 Helium documentation. You must follow carrefuly each step to set up your PlatformIO IDE.
The program has been widely inspired by the Wisblock weather monitoring project from the official GitHub repository RAKWireless.
The payload follows the Cayenne LPP structure. So, the payload has been adapted in order to be compatible with all LoRa nodes which are built on RAK Unified Interface.
Indeed, I already own a RAK7204 environmental sensor and I want to share the same Helium flows with it and my Wisblock Kit 1 (See section Helium Flows).
The librarie CayenneLPP.h is used in order to build the data payload.
- Data Channel : 02
- Data Type : 67
lpp.addTemperature(2, temp);- Data Channel : 07
- Data Type : 68
lpp.addRelativeHumidity(7, hum);- Data Channel : 06
- Data Type : 73
lpp.addBarometricPressure(6, pres * 10);Only this data has been added to the channel 12 with the original RAK7204 payload.
- Data Channel : 12
- Data Type : 65
lpp.addLuminosity(12, result.lux);- Data Channel : 8
- Data Type : 02
lpp.addAnalogInput(8, vbat / 1000);The data received from the device are encoded in Cayenne LPP format and sent as is to MyDevices Cayenne. MyDevices Cayenne expects a structured buffer so as to be loaded.
Regarding the Ubidots API, the expected format is JSON. This is performed by the JavaScript function that decodes the LPP buffer to JSON before being sent to Ubidots.
As explained earlier, data are transformed into JSON Format before being forwarded to Ubidots.
A common JavaScript function is shared with my WisNode RAK7204 as well as my WisBlock Kit 1. This same function also decodes data as expected by Ubidots API.
Down below, the result of the JavaScript decoding function expected by the Ubidots API :
{
"id": "3ef5a334-2901-498b-9683-6fc902e45542",
"name": "Ubidots",
"status": "success",
"decoded_payload": {
"barometer": {
"context": {
"uplink_fcnt": 156
},
"timestamp": 1646124272844,
"value": 1020
},
"battery": {
"context": {
"uplink_fcnt": 156
},
"timestamp": 1646124272844,
"value": 4.12
},
"humidity": {
"context": {
"uplink_fcnt": 156
},
"timestamp": 1646124272844,
"value": 63
},
"lux": {
"context": {
"uplink_fcnt": 156
},
"timestamp": 1646124272844,
"value": 262
},
"temperature": {
"context": {
"uplink_fcnt": 156
},
"timestamp": 1646124272844,
"value": 9.6
}
}
}In order to send data from Helium to Ubidots, you will have to create an Helium Plugin. In my case, I have created the plugin from Helium console directly. Follow the section "creating the plugin from Helium" of this article to achieve that.
The data received from the RAK4631 will be decoded by the JavaScript Decoder function from Helium. The Hexadecimal data received from the device will be decoded and transformed into a JSON payload that will be parsed and loaded by the Ubidots API.
The device is automatically provisioned by the Ubidots API as soon as Ubidots receives data from an unknown device.
Down below the result of the integration of data received from Helium to Ubidots :
Right here, a dashboard whose data comes from my Home Environmental Sensor RAK7204 and my Outdoor Weather Station WisBlock Kit 1.
As explained previously for Ubidots, it is required to connect Helium to your MyDevices Cayenne account. :warning: In contrary to Ubidots platform, before ingesting data, you must add your device into MyDevices Cayenne yourself.
Below the result of the integration of LPP data received from Helium to MyDevices Cayenne :
Type of battery used :
- Battery Samsung INR18650-32E 3100mAh - 6.4A - 18650 - Li-ion
After several days of data transmission (every 15 minutes), I noticed that the current drops very quickly and that the module drained the current from 4.03 Volts to 3.66 Volts in less than seven days.
Actually, the program doesn't take into account power consumption related issues. I have analysed the power consumption and I observed that the module consumes 6.3 mA at rest. Also when data was being sent over the LoRaWan, I have noticed that the current's consumption reached a peak of 72 mA.
The current consumption's graph for seven days :
The trick to benefit from deep sleep mode with the Nordic nRF52840 is to use semaphores provided by the embedded Operating System FreeRTOS.
This topic has been well developed in this article : how to reduce the Power Consumption of WisBlock Solution.
Down below, the current consumption's graph after one month supplied with power saving mode. As you can see, the curve is flat 🚀 :
/** Semaphore used by events to wake up loop task */
SemaphoreHandle_t taskEvent = NULL;
/** Timer to wakeup task frequently and send message */
SoftwareTimer taskWakeupTimer;
// Timing between two sending data
long SLEEP_TIME = 900000;
void periodicWakeup(TimerHandle_t unused)
{
// Give the semaphore, so the loop task will wake up
xSemaphoreGiveFromISR(taskEvent, pdFALSE);
}
...
void setup() {
... // do other initialization before to take the semaphore
// Create the loopTask semaphore
taskEvent = xSemaphoreCreateBinary();
// Initialize semaphore
xSemaphoreGive(taskEvent);
// Start the timer that will wakeup the loop frequently
taskWakeupTimer.begin(SLEEP_TIME, periodicWakeup);
taskWakeupTimer.start();
// Take the semaphore so the loop will go to sleep until an event happens
xSemaphoreTake(taskEvent, 10);
}
void loop()
{
// Sleep until we are woken up by an event
if (xSemaphoreTake(taskEvent, portMAX_DELAY) == pdTRUE)
{
// Send Data
send_lora_frame();
// Go back to sleep
xSemaphoreTake(taskEvent, 10);
}
}In order to track the power consumption, the battery voltage is read and sent at each interrupt.
Below, the main code that evaluates the battery voltage :
// Battery Voltage
#define PIN_VBAT WB_A0
uint32_t vbat_pin = PIN_VBAT;
#define VBAT_MV_PER_LSB (0.73242188F) // 3.0V ADC range and 12 - bit ADC resolution = 3000mV / 4096
#define VBAT_DIVIDER_COMP (1.73) // Compensation factor for the VBAT divider, depend on the board
#define REAL_VBAT_MV_PER_LSB (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
/**
* @brief Get RAW Battery Voltage
*/
float readVBAT(void)
{
float raw;
// Get the raw 12-bit, 0..3000mV ADC value
raw = analogRead(vbat_pin);
return raw * REAL_VBAT_MV_PER_LSB;
}
void setup()
{
...
// Initialize Battery Voltage
// Set the analog reference to 3.0V (default = 3.6V)
analogReference(AR_INTERNAL_3_0);
// Set the resolution to 12-bit (0..4095)
analogReadResolution(12); // Can be 8, 10, 12 or 14
// Let the ADC settle
delay(1);
// Get a single ADC sample and throw it away
readVBAT();
}