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A program for collecting data from an SDS-011 PM 2.5 sensor
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#include <ArduinoJson.h> | |
#include <WiFi.h> | |
#include <SdsDustSensor.h> | |
#include <PubSubClient.h> | |
// v1.0 - 2019-06-16 - Initial public release of script | |
// v1.1 - 2019-06-17 - Turn off sensor if resetting due to lack of connectivity | |
// XXX Change these to your WiFi details | |
// It may be a good idea to run a separate, segregated WLAN for | |
// Internet of Things devices. Up to you. | |
#define WIFI_SSID "CHANGE ME" | |
#define WIFI_PASS "CHANGE ME" | |
// XXX Change this if running more than one sensor | |
#define CLIENT_ID "airquality0" | |
// Which topic to publish to | |
#define TOPIC "airquality" | |
// How many retries for wifi connection before reset | |
#define MAX_TRIES 5 | |
// How many samples to average out per round of measurement | |
#define N_SAMPLES_PER_ROUND 10 | |
// What pin is the battery on | |
#define BATTERY_PIN 34 | |
// What pin is the onboard LED on | |
#define ONBOARD_LED 2 | |
#define SLEEP_SECONDS 30 | |
#define SEC_TO_USEC_FACTOR 1000000 | |
// measureJson from ArduinoJson reports the JSON size WITHOUT trailing null byte, | |
// this helper macro adds it | |
#define MEASURE_JSON_BUFFER(doc) (measureJson(doc) + 1) | |
// The dust/PM sensor is on Serial2 | |
SdsDustSensor sds(Serial2); | |
// Set up a MQTT client on WiFi | |
WiFiClient wifiClient; | |
PubSubClient mqtt(wifiClient); | |
// TODO: verify battery voltage reporting | |
void wifi_reconnect(); | |
void mqtt_reconnect(); | |
void setup_sensor(); | |
int do_measurement(float* avg_pm25, float* avg_pm10); | |
float get_battery(int n_samples); | |
// The main entry point | |
void setup() { | |
// Configure GPIO | |
pinMode(ONBOARD_LED, OUTPUT); | |
digitalWrite(ONBOARD_LED, LOW); | |
adcAttachPin(BATTERY_PIN); | |
analogSetPinAttenuation(BATTERY_PIN, ADC_11db); | |
// Configure debug | |
Serial.begin(115200); | |
// Configure the SDS sensor | |
setup_sensor(); | |
// Get sensor info | |
Serial.printf("[SDS] version %s\n", sds.queryFirmwareVersion().toString().c_str()); // prints firmware version | |
// Connect to MQTT - this also gives time for the sensor to stabilise (hacky, but w/e) | |
wifi_reconnect(); | |
mqtt_reconnect(); | |
// Do the measurement and turn off the sensor when done | |
float avg_pm25, avg_pm10; | |
int n_fail = do_measurement(&avg_pm25, &avg_pm10); | |
sds.sleep(); | |
// Get battery level (average of 5 measurements) | |
float battery_voltage = get_battery(5); | |
Serial.printf("battery = %.2fv\n", battery_voltage); | |
// Put everything into a JSON document | |
StaticJsonDocument<512> doc; | |
doc["client"] = CLIENT_ID; | |
doc["pm25"] = avg_pm25; | |
doc["pm10"] = avg_pm10; | |
doc["batt"] = battery_voltage; | |
doc["err"] = n_fail; | |
// How much size do we need to allocate for the JSON buffer? | |
size_t payload_len = MEASURE_JSON_BUFFER(doc); | |
char payload[payload_len]; | |
// Serialize the JSON document and publish it to MQTT | |
serializeJson(doc, payload, payload_len); | |
mqtt.publish(TOPIC, payload); | |
// Wait to make sure everything is published | |
delay(500); | |
mqtt.loop(); | |
// And now, shut down WiFi and go to sleep. | |
digitalWrite(ONBOARD_LED, LOW); | |
WiFi.disconnect(true); | |
ESP.deepSleep(SLEEP_SECONDS * SEC_TO_USEC_FACTOR); | |
} | |
void loop() { | |
// Never reached | |
} | |
// Connects to WiFi, blinks onboard LED while connecting | |
void wifi_reconnect() { | |
digitalWrite(ONBOARD_LED, LOW); | |
// Connect to WiFi | |
Serial.println("[WL ] connecting"); | |
WiFi.begin(WIFI_SSID, WIFI_PASS); | |
for (int n = 0; n < MAX_TRIES && WiFi.status() != WL_CONNECTED; n++) { | |
digitalWrite(ONBOARD_LED, LOW); | |
delay(500); | |
digitalWrite(ONBOARD_LED, HIGH); | |
delay(500); | |
} | |
if (WiFi.status() != WL_CONNECTED) { | |
digitalWrite(ONBOARD_LED, LOW); | |
Serial.println("[WL ] max tries exceeded, trying to reboot"); | |
WiFi.disconnect(); | |
sds.sleep(); | |
delay(1000); | |
ESP.deepSleep(SLEEP_SECONDS * SEC_TO_USEC_FACTOR); | |
} | |
Serial.println("[WL ] connected"); | |
} | |
// Connects to MQTT, possibly blinks onboard LED | |
void mqtt_reconnect() { | |
mqtt.setServer("iot-server.lan", 1883); | |
for (int tries = 0; tries < MAX_TRIES && !mqtt.connected(); tries++) { | |
digitalWrite(ONBOARD_LED, HIGH); | |
if (!mqtt.connect(CLIENT_ID)) { | |
digitalWrite(ONBOARD_LED, LOW); | |
Serial.printf("[MQ ] fail: %d\n", mqtt.state()); | |
delay(500); | |
} | |
} | |
if (mqtt.connected()) { | |
digitalWrite(ONBOARD_LED, HIGH); | |
} else { | |
digitalWrite(ONBOARD_LED, LOW); | |
Serial.println("[MQ ] max tries exceeded, trying to reboot"); | |
WiFi.disconnect(true); | |
sds.sleep(); | |
delay(1000); | |
ESP.deepSleep(SLEEP_SECONDS * SEC_TO_USEC_FACTOR); | |
} | |
} | |
// Wakes up and resets the SDS-011 to a known state | |
void setup_sensor() { | |
sds.begin(); | |
sds.wakeup(); | |
sds.setQueryReportingMode(); // only report when asked | |
sds.setContinuousWorkingPeriod(); // run continuously | |
} | |
// Performs a measurement on the SDS-011 | |
int do_measurement(float* avg_pm25, float* avg_pm10) { | |
int n_ok = 0; | |
int n_fail = 0; | |
float sum_pm25 = 0.0f; | |
float sum_pm10 = 0.0f; | |
for (int n = 0; n < N_SAMPLES_PER_ROUND; n++) { | |
Serial.print("*"); | |
PmResult res = sds.queryPm(); | |
if (res.isOk()) { | |
n_ok++; | |
sum_pm25 += res.pm25; | |
sum_pm10 += res.pm10; | |
} else { | |
n_fail++; | |
} | |
mqtt.loop(); | |
delay(1000); | |
} | |
Serial.println(); | |
*avg_pm25 = sum_pm25 / n_ok; | |
*avg_pm10 = sum_pm10 / n_ok; | |
return n_fail; | |
} | |
// Reads battery level | |
float get_battery(int n_samples) { | |
float sum_reading = 0.0; | |
for (int n = 0; n < n_samples; n++) { | |
int batteryAdcCount = analogRead(BATTERY_PIN); | |
// Battery voltage is given by the ADC as x/4096 * 3.3 for the voltage divider | |
// and * 2 for the full voltage. | |
sum_reading += ((float) batteryAdcCount) / 4096.0 * 3.3 * 2; | |
} | |
return sum_reading / ((float) n_samples); | |
} |
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