From 13bb23f43c1d9239ab765afee9a3040302148b63 Mon Sep 17 00:00:00 2001
From: "Colin B." <vogon@outlook.com>
Date: Fri, 11 Apr 2025 15:35:54 -0700
Subject: [PATCH] support manually shutting off power to the PMSA003I sensor
 when we aren't doing a telemetry reading

---
 src/modules/Telemetry/AirQualityTelemetry.cpp | 60 +++++++++++++++----
 src/modules/Telemetry/AirQualityTelemetry.h   | 14 +++++
 2 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/src/modules/Telemetry/AirQualityTelemetry.cpp b/src/modules/Telemetry/AirQualityTelemetry.cpp
index 392bd6148..c1a70d2e7 100644
--- a/src/modules/Telemetry/AirQualityTelemetry.cpp
+++ b/src/modules/Telemetry/AirQualityTelemetry.cpp
@@ -14,6 +14,10 @@
 #include "main.h"
 #include <Throttle.h>
 
+#ifndef PMSA003I_WARMUP_MS
+#define PMSA003I_WARMUP_MS 30000
+#endif
+
 int32_t AirQualityTelemetryModule::runOnce()
 {
     /*
@@ -34,6 +38,12 @@ int32_t AirQualityTelemetryModule::runOnce()
 
         if (moduleConfig.telemetry.air_quality_enabled) {
             LOG_INFO("Air quality Telemetry: init");
+
+#ifdef PMSA003I_ENABLE_PIN
+            pinMode(PMSA003I_ENABLE_PIN, OUTPUT);
+            digitalWrite(PMSA003I_ENABLE_PIN, 0);
+#endif /* PMSA003I_ENABLE_PIN */
+
             if (!aqi.begin_I2C()) {
 #ifndef I2C_NO_RESCAN
                 LOG_WARN("Could not establish i2c connection to AQI sensor. Rescan");
@@ -63,21 +73,45 @@ int32_t AirQualityTelemetryModule::runOnce()
         if (!moduleConfig.telemetry.air_quality_enabled)
             return disable();
 
-        if (((lastSentToMesh == 0) ||
-             !Throttle::isWithinTimespanMs(lastSentToMesh, Default::getConfiguredOrDefaultMsScaled(
-                                                               moduleConfig.telemetry.air_quality_interval,
-                                                               default_telemetry_broadcast_interval_secs, numOnlineNodes))) &&
-            airTime->isTxAllowedChannelUtil(config.device.role != meshtastic_Config_DeviceConfig_Role_SENSOR) &&
-            airTime->isTxAllowedAirUtil()) {
-            sendTelemetry();
-            lastSentToMesh = millis();
-        } else if (service->isToPhoneQueueEmpty()) {
-            // Just send to phone when it's not our time to send to mesh yet
-            // Only send while queue is empty (phone assumed connected)
-            sendTelemetry(NODENUM_BROADCAST, true);
+        switch (state) {
+#ifdef PMSA003I_ENABLE_PIN
+            case State::IDLE:
+                // sensor is in standby; fire it up and sleep
+                LOG_DEBUG("runOnce(): state = idle");
+                digitalWrite(PMSA003I_ENABLE_PIN, 1);
+                state = State::ACTIVE;
+
+                return PMSA003I_WARMUP_MS;
+#endif /* PMSA003I_ENABLE_PIN */
+            case State::ACTIVE:
+                // sensor is already warmed up; grab telemetry and send it
+                LOG_DEBUG("runOnce(): state = active");
+
+                if (((lastSentToMesh == 0) ||
+                    !Throttle::isWithinTimespanMs(lastSentToMesh, Default::getConfiguredOrDefaultMsScaled(
+                                                                    moduleConfig.telemetry.air_quality_interval,
+                                                                    default_telemetry_broadcast_interval_secs, numOnlineNodes))) &&
+                    airTime->isTxAllowedChannelUtil(config.device.role != meshtastic_Config_DeviceConfig_Role_SENSOR) &&
+                    airTime->isTxAllowedAirUtil()) {
+                    sendTelemetry();
+                    lastSentToMesh = millis();
+                } else if (service->isToPhoneQueueEmpty()) {
+                    // Just send to phone when it's not our time to send to mesh yet
+                    // Only send while queue is empty (phone assumed connected)
+                    sendTelemetry(NODENUM_BROADCAST, true);
+                }
+
+                // put sensor back to sleep
+#if PMSA003I_ENABLE_PIN
+                digitalWrite(PMSA003I_ENABLE_PIN, 0);
+                state = State::IDLE;
+#endif /* PMSA003I_ENABLE_PIN */
+
+                return sendToPhoneIntervalMs;
+            default:
+                return disable();
         }
     }
-    return sendToPhoneIntervalMs;
 }
 
 bool AirQualityTelemetryModule::handleReceivedProtobuf(const meshtastic_MeshPacket &mp, meshtastic_Telemetry *t)
diff --git a/src/modules/Telemetry/AirQualityTelemetry.h b/src/modules/Telemetry/AirQualityTelemetry.h
index 3b983bd56..6d7398a72 100644
--- a/src/modules/Telemetry/AirQualityTelemetry.h
+++ b/src/modules/Telemetry/AirQualityTelemetry.h
@@ -23,6 +23,14 @@ class AirQualityTelemetryModule : private concurrency::OSThread, public Protobuf
         setIntervalFromNow(10 * 1000);
         aqi = Adafruit_PM25AQI();
         nodeStatusObserver.observe(&nodeStatus->onNewStatus);
+
+#ifdef PMSA003I_ENABLE_PIN
+        // the PMSA003I sensor uses about 300mW on its own; support powering it off when it's not actively taking
+        // a reading
+        state = State::IDLE;
+#else
+        state = State::ACTIVE;
+#endif
     }
 
   protected:
@@ -42,6 +50,12 @@ class AirQualityTelemetryModule : private concurrency::OSThread, public Protobuf
     bool sendTelemetry(NodeNum dest = NODENUM_BROADCAST, bool wantReplies = false);
 
   private:
+    enum State {
+      IDLE = 0,
+      ACTIVE = 1,
+    };
+
+    State state;
     Adafruit_PM25AQI aqi;
     PM25_AQI_Data data = {0};
     bool firstTime = true;