From 6b44b5786e056a121f5e96edf1fbc6b940ce69b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20G=C3=B6ttgens?= <tgoettgens@gmail.com>
Date: Mon, 16 Feb 2026 17:07:07 +0100
Subject: [PATCH] fix detection of SCD30 by checking if the size of the return
 from a 2 byte register read is correct (#9664)

* fix detection of SCD30 by checking if thee size of the return from a 2 byte register read is correct
fix signedness warning in PMSA003 sensor code.

* Add alternate path for LPS22HB

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* check EndTransmission for errors and compare returned length to expected value

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/detect/ScanI2CTwoWire.cpp                 | 34 ++++++++++++++++---
 src/detect/ScanI2CTwoWire.h                   |  2 ++
 .../Telemetry/Sensor/PMSA003ISensor.cpp       |  2 +-
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/detect/ScanI2CTwoWire.cpp b/src/detect/ScanI2CTwoWire.cpp
index df0fad792..c58a58518 100644
--- a/src/detect/ScanI2CTwoWire.cpp
+++ b/src/detect/ScanI2CTwoWire.cpp
@@ -117,6 +117,25 @@ uint16_t ScanI2CTwoWire::getRegisterValue(const ScanI2CTwoWire::RegisterLocation
     return value;
 }
 
+bool ScanI2CTwoWire::i2cCommandResponseLength(ScanI2C::DeviceAddress addr, uint16_t command, uint8_t expectedLength) const
+{
+    TwoWire *i2cBus = fetchI2CBus(addr);
+    i2cBus->beginTransmission(addr.address);
+    if (command > 0xFF) {
+        i2cBus->write((uint8_t)(command >> 8));
+    }
+    i2cBus->write((uint8_t)(command & 0xFF));
+    if (i2cBus->endTransmission() != 0) {
+        return false;
+    }
+    delay(20);
+    uint8_t received = i2cBus->requestFrom(addr.address, expectedLength);
+    bool match = (received == expectedLength);
+    while (i2cBus->available())
+        i2cBus->read();
+    return match;
+}
+
 /// for SEN5X detection
 // Note, this code needs to be called before setting the I2C bus speed
 // for the screen at high speed. The speed needs to be at 100kHz, otherwise
@@ -432,8 +451,7 @@ void ScanI2CTwoWire::scanPort(I2CPort port, uint8_t *address, uint8_t asize)
                 if (getRegisterValue(ScanI2CTwoWire::RegisterLocation(addr, 0x7E), 2) == 0x5449) {
                     type = OPT3001;
                     logFoundDevice("OPT3001", (uint8_t)addr.address);
-                } else if (getRegisterValue(ScanI2CTwoWire::RegisterLocation(addr, 0x89), 6) !=
-                           0) { // unique SHT4x serial number (6 bytes inc. CRC)
+                } else if (i2cCommandResponseLength(addr, 0x89, 6)) { // SHT4x serial number (6 bytes inc. CRC)
                     type = SHT4X;
                     logFoundDevice("SHT4X", (uint8_t)addr.address);
                 } else {
@@ -458,13 +476,19 @@ void ScanI2CTwoWire::scanPort(I2CPort port, uint8_t *address, uint8_t asize)
                 break;
 
             case LPS22HB_ADDR_ALT:
-                registerValue = getRegisterValue(ScanI2CTwoWire::RegisterLocation(addr, 0xD060), 48); // get device marking
-                if (registerValue != 0) {
+                // SFA30 detection: send 2-byte command 0xD060 (Get Device Marking) and check for 48-byte response
+                if (i2cCommandResponseLength(addr, 0xD060, 48)) {
                     type = SFA30;
                     logFoundDevice("SFA30", (uint8_t)addr.address);
                     break;
                 }
-                // TODO - What happens with these two?
+                // Fallback: LPS22HB detection at alternate address using WHO_AM_I register (0x0F == 0xB1)
+                registerValue = getRegisterValue(ScanI2CTwoWire::RegisterLocation(addr, 0x0F), 1);
+                if (registerValue == 0xB1) {
+                    type = LPS22HB;
+                    logFoundDevice("LPS22HB", (uint8_t)addr.address);
+                }
+                break;
                 SCAN_SIMPLE_CASE(LPS22HB_ADDR, LPS22HB, "LPS22HB", (uint8_t)addr.address)
                 SCAN_SIMPLE_CASE(QMC6310U_ADDR, QMC6310U, "QMC6310U", (uint8_t)addr.address)
 
diff --git a/src/detect/ScanI2CTwoWire.h b/src/detect/ScanI2CTwoWire.h
index c5b791920..841a8b946 100644
--- a/src/detect/ScanI2CTwoWire.h
+++ b/src/detect/ScanI2CTwoWire.h
@@ -55,6 +55,8 @@ class ScanI2CTwoWire : public ScanI2C
 
     uint16_t getRegisterValue(const RegisterLocation &, ResponseWidth, bool) const;
 
+    bool i2cCommandResponseLength(DeviceAddress addr, uint16_t command, uint8_t expectedLength) const;
+
     DeviceType probeOLED(ScanI2C::DeviceAddress) const;
 
     static void logFoundDevice(const char *device, uint8_t address);
diff --git a/src/modules/Telemetry/Sensor/PMSA003ISensor.cpp b/src/modules/Telemetry/Sensor/PMSA003ISensor.cpp
index 069931e21..e34b70a1f 100644
--- a/src/modules/Telemetry/Sensor/PMSA003ISensor.cpp
+++ b/src/modules/Telemetry/Sensor/PMSA003ISensor.cpp
@@ -67,7 +67,7 @@ bool PMSA003ISensor::getMetrics(meshtastic_Telemetry *measurement)
 #endif /* CAN_RECLOCK_I2C */
 #endif /* PMSA003I_I2C_CLOCK_SPEED */
 
-    _bus->requestFrom(_address, PMSA003I_FRAME_LENGTH);
+    _bus->requestFrom(_address, (uint8_t)PMSA003I_FRAME_LENGTH);
     if (_bus->available() < PMSA003I_FRAME_LENGTH) {
         LOG_WARN("%s read failed: incomplete data (%d bytes)", sensorName, _bus->available());
         return false;