sht3x: formatting, fix visibility of virtual

also experiment a bit with status register in log

code/espurna/sensors/SHT3XI2CSensor.h

@@ -29,7 +29,6 @@ class SHT3XI2CSensor : public I2CSensor<> {
 
         // Initialization method, must be idempotent
         void begin() override {
-
             if (!_dirty) return;
 
             // I2C auto-discover
@@ -46,7 +45,6 @@ class SHT3XI2CSensor : public I2CSensor<> {
 
             _ready = true;
             _dirty = false;
-
         }
 
         // Descriptive name of the sensor
@@ -66,7 +64,6 @@ class SHT3XI2CSensor : public I2CSensor<> {
 
         // Pre-read hook (usually to populate registers with up-to-date data)
         void pre() override {
-
             _error = SENSOR_ERROR_OK;
 
             const auto address = lockedAddress();
@@ -78,82 +75,98 @@ class SHT3XI2CSensor : public I2CSensor<> {
 
             unsigned char buffer[6];
             i2c_read_buffer(address, buffer, std::size(buffer));
-            
-            if ((CRC8(buffer[0],buffer[1],buffer[2])) && (CRC8(buffer[3],buffer[4],buffer[5]))) {
-                // cTemp msb, cTemp lsb, cTemp crc, humidity msb, humidity lsb, humidity crc
+
+            // result bytes are as follows
+            // cTemp msb, cTemp lsb, cTemp crc, humidity msb, humidity lsb, humidity crc
+            if ((_crc8(buffer[0], buffer[1], buffer[2])) && (_crc8(buffer[3], buffer[4], buffer[5]))) {
                 _temperature = ((((buffer[0] * 256.0) + buffer[1]) * 175) / 65535.0) - 45;
                 _humidity = ((((buffer[3] * 256.0) + buffer[4]) * 100) / 65535.0);
-            }
-            else {
+            } else {
                 _error = SENSOR_ERROR_CRC;
             }
-            #if SENSOR_DEBUG
-            status_register();
-            #endif
+
+#if SENSOR_DEBUG
+            _statusRegister();
+#endif
         }
-        
+
+        // Current value for slot # index
+        double value(unsigned char index) override {
+            if (index == 0) return _temperature;
+            if (index == 1) return _humidity;
+            return 0;
+        }
+
+    private:
+
         // Read the status register and output to Debug log
-        void status_register() {
+        void _statusRegister() {
             const auto address = lockedAddress();
-            
-            unsigned char buffer[3];
-            bool crc, cmd, htr;
-            // Read status register
+
+            // Request status register reading
             i2c_write_uint8(address, 0xF3, 0x2D);
             espurna::time::blockingDelay(
                 espurna::duration::Milliseconds(20));
+
+            unsigned char buffer[3];
             i2c_read_buffer(address, buffer, std::size(buffer));
-            if (CRC8(buffer[0],buffer[1],buffer[2])) {
+
+            if (_crc8(buffer[0],buffer[1],buffer[2])) {
                 // see https://sensirion.com/resource/datasheet/sht3x-d
-                crc = buffer[1] & 0b00000001;
-                cmd = buffer[1] & 0b00000010;
-                htr = buffer[0] & 0b00100000;
-                DEBUG_MSG_P(PSTR("[SHT3X] Status %02X%02X crc:%u cmd:%u htr:%u\n"), buffer[0], buffer[1], crc, cmd, htr);
+                uint16_t status = (buffer[0] << 8) | (buffer[1] & 0xff);
+                auto bit = [&](uint16_t offset) {
+                    return (status & (1 << offset)) ? '1' : '0';
+                };
+                DEBUG_MSG_P(PSTR("[SHT3X] Status 0x%04X - crc:%c cmd:%c rst:%c tta:%c rhta:%c htr:%c alrt:%c\n"),
+                    status,
+                    bit(0),   // last write crc status
+                    bit(1),   // last command status
+                    bit(4),   // system reset detected
+                    bit(10),  // T tracking alert
+                    bit(11),  // RH tracking alert
+                    bit(13),  // heater status
+                    bit(15)); // alert pending status (1 when at least one alert)
             }
             else {
-                DEBUG_MSG_P(PSTR("[SHT3X] Checksum error\n"));
+                DEBUG_MSG_P(PSTR("[SHT3X] Checksum error when reading status register\n"));
             }
+
             // Clear status register
             i2c_write_uint8(address, 0x30, 0x41);
         }
 
-        // Current value for slot # index
-        double value(unsigned char index) override {
-            if (index == 0) return _temperature;
-            if (index == 1) return _humidity;
-            return 0;
-        }
-
-    protected:
-
-        double _temperature = 0;
-        unsigned char _humidity = 0;
-        
-        bool 	CRC8(uint8_t MSB, uint8_t LSB, uint8_t CRC) {
+        bool _crc8(uint8_t msb, uint8_t lsb, uint8_t expected) {
             /*
             * adapted from https://github.com/Risele/SHT3x/blob/master/SHT3x.cpp
-            *	Name  : CRC-8
-            *	Poly  : 0x31	x^8 + x^5 + x^4 + 1
-            *	Init  : 0xFF
-            *	Revert: false
-            *	XorOut: 0x00
-            *	Check : for 0xBE,0xEF CRC is 0x92
+            *   Name  : CRC-8
+            *   Poly  : 0x31 x^8 + x^5 + x^4 + 1
+            *   Init  : 0xFF
+            *   Revert: false
+            *   XorOut: 0x00
+            *   Check : for 0xBE,0xEF CRC is 0x92
             */
-            uint8_t crc = 0xFF;
-            uint8_t i;
-            crc ^= MSB;
+            static constexpr uint8_t Init { 0xFF };
+            static constexpr uint8_t Mask { 0x80 };
+            static constexpr uint8_t Poly { 0x31 };
 
-            for (i = 0; i < 8; i++)
-          	crc = crc & 0x80 ? (crc << 1) ^ 0x31 : crc << 1;
+            uint8_t crc = Init;
 
-            crc ^= LSB;
-            for (i = 0; i < 8; i++)
-          	crc = crc & 0x80 ? (crc << 1) ^ 0x31 : crc << 1;
+            crc ^= msb;
+            for (size_t i = 0; i < 8; ++i) {
+                crc = crc & Mask ? (crc << 1) ^ Poly : crc << 1;
+            }
 
-            if (crc == CRC) return true;
-            return false;
+            crc ^= lsb;
+            for (size_t i = 0; i < 8; ++i) {
+                crc = crc & Mask ? (crc << 1) ^ Poly : crc << 1;
+            }
+
+            return crc == expected;
         }
 
+        double _temperature = 0;
+        unsigned char _humidity = 0;
+
 };
 
 #endif // SENSOR_SUPPORT && SHT3X_I2C_SUPPORT