Apologies for the long read, I am trying to learn and make sense of this as I go. I am trying to use a SDC40 sensor over I2C to read CO2, temperature, and humidity. Originally I thought my errors may have been a conflict with an existing instance of Wire, however, the example sketch provided within the library "Sensirion I2C SCD4x" by Sensirion wont compile either.
If I switch the board from Arduino Uno WiFi Rev2 to something in the AVR range such as the standard Arduino Uno Wifi then everything compiles just fine. I am assuming something with the megaAVR boards conflicts with how this sensor expects to use I2C.
Compilation Errors:
In file included from C:\Users\d4sturt\Documents\Arduino\libraries\Sensirion_Core\src\SensirionI2CCommunication.h:38:0,
from C:\Users\d4sturt\Documents\Arduino\libraries\Sensirion_Core\src\SensirionI2CCommunication.cpp:31:
C:\Users\d4sturt\AppData\Local\Arduino15\packages\arduino\hardware\megaavr\1.8.8\libraries\Wire\src/Wire.h: In static member function 'static uint16_t SensirionI2CCommunication::receiveFrame(uint8_t, size_t, SensirionI2CRxFrame&, TwoWire&, CrcPolynomial)':
C:\Users\d4sturt\AppData\Local\Arduino15\packages\arduino\hardware\megaavr\1.8.8\libraries\Wire\src/Wire.h:64:12: note: candidate 1: size_t TwoWire::requestFrom(int, int, int)
size_t requestFrom(int, int, int);
^~~~~~~~~~~
C:\Users\d4sturt\AppData\Local\Arduino15\packages\arduino\hardware\megaavr\1.8.8\libraries\Wire\src/Wire.h:62:12: note: candidate 2: virtual size_t TwoWire::requestFrom(uint8_t, size_t, bool)
size_t requestFrom(uint8_t, size_t, bool);
^~~~~~~~~~~
When I look into the Class found in "SensirionI2CCommunication.h" I see:
class SensirionI2CCommunication {
public:
static uint16_t sendFrame(uint8_t address, SensirionI2CTxFrame& frame,
TwoWire& i2cBus);
static uint16_t receiveFrame(uint8_t address, size_t numBytes,
SensirionI2CRxFrame& frame, TwoWire& i2cBus,
CrcPolynomial poly = CRC31_ff);
};
The sensor is supposed to return CO2, temperature, and humidity. In the sketch they are defined as uint16_t, float, and float respectively. Looking at the function which handles sending/receiving I can see that all values are declared as uint16_t and then later converted to match the expected data types:
uint16_t SensirionI2CScd4x::readMeasurementTicks(uint16_t& co2,
uint16_t& temperature,
uint16_t& humidity) {
uint16_t error;
uint8_t buffer[9];
SensirionI2CTxFrame txFrame(buffer, 9);
error = txFrame.addCommand(0xEC05);
if (error) {
return error;
}
error = SensirionI2CCommunication::sendFrame(SCD4X_I2C_ADDRESS, txFrame,
*_i2cBus);
if (error) {
return error;
}
delay(1);
SensirionI2CRxFrame rxFrame(buffer, 9);
error = SensirionI2CCommunication::receiveFrame(SCD4X_I2C_ADDRESS, 9,
rxFrame, *_i2cBus);
if (error) {
return error;
}
error |= rxFrame.getUInt16(co2);
error |= rxFrame.getUInt16(temperature);
error |= rxFrame.getUInt16(humidity);
return error;
}
uint16_t SensirionI2CScd4x::readMeasurement(uint16_t& co2, float& temperature,
float& humidity) {
uint16_t error;
uint16_t temperatureTicks;
uint16_t humidityTicks;
error = readMeasurementTicks(co2, temperatureTicks, humidityTicks);
if (error) {
return error;
}
temperature = static_cast<float>(temperatureTicks * 175.0 / 65535.0 - 45.0);
humidity = static_cast<float>(humidityTicks * 100.0 / 65535.0);
return NoError;
}
If I am interpreting the errors correctly then Wire is expecting the result to be all integers as referenced as the first candidate in the error description, while Sensirion is expecting all uint16_t's.
I am also going to assume that the second candidate in the output window is only for a single frame of data (uint8_t, size_t, bool). Not sure if this is correct with my limited knowledge of how Wire and I2C work.
At this point I do not know what to change or if using this sensor is even feasible. Please let me know if there is any additional detail needed or more importantly...a solution.
It is the parameters of the functions of the Wire library.
).
and it is for the third parameter of Wire.requestFrom() which is never used anyway, so double 