Fixed wrong shunt voltage reading

lib/INA233/INA233.cpp

@@ -23,7 +23,7 @@ uint16_t get_word(uint8_t address, uint8_t reg) {
     return (data[1] << 8) | data[0];
 }
 
-String INA233::print_device_number() {
+String INA233::get_device_model() {
     char data[7]; // Array size includes space for the null terminator
 
     // Request data from the PMBus device
@@ -57,6 +57,13 @@ void sendWord(uint8_t deviceAddress, uint8_t registerAddress, uint16_t value) {
   Wire.endTransmission();
 }
 
+void sendByte(uint8_t deviceAddress, uint8_t registerAddress, uint8_t value) {
+    Wire.beginTransmission(deviceAddress);
+    Wire.write(registerAddress); // Send the register address
+    Wire.write((uint8_t)value); // Send the low byte first
+    Wire.endTransmission();
+  }
+
 INA233::INA233(const uint8_t address, TwoWire *wire)
 {
   _address     = address;
@@ -109,8 +116,18 @@ float INA233::getBusVoltage() {
 }
 
 float INA233::getShuntVoltage() {
-    uint16_t rawVoltage = get_word(INA233::_address, REGISTER_READ_VSHUNT);
-    float voltage = rawVoltage * pow(10,-4);
+    int16_t rawVoltage = get_word(INA233::_address, REGISTER_READ_VSHUNT); // Read raw voltage (16-bit register)
+
+    // Convert from two's complement to an integer value
+    // If the MSB (most significant bit) is set, the number is negative
+    if (rawVoltage & 0x8000) {  // Check if MSB (bit 15) is set
+        rawVoltage = rawVoltage - 0x10000; // Convert two's complement negative number
+    }
+
+    // Convert value according to the datasheet
+    // LSB: 2.5 μV per bit -> Multiply by 2.5e-6 to convert to volts
+    float voltage = rawVoltage * 2.5e-6;
+
     return voltage;
 }
 
@@ -174,4 +191,8 @@ void INA233::setShuntVoltageConversionTime(ConversionTime conversion_time) {
 
 uint16_t INA233::getConfigRegister() {
     return get_word(INA233::_address, REGISTER_CONFIGURATION);
+}
+
+void INA233::reset() {
+    sendByte(INA233::_address, 0x12, 0x00);
 }