I am trying to read data off two sht31 temp and humidity sensors. one is set to 0x44 and the other is set to 0x45
i can read one with the following code but I cant seem to read the second one. I cant find any way online of doing it or any examples
I get an error if i define twice by doing #define Addr 0x44 #define Addr2 0x45
any way to do this?
thank you for your help
Ian
// Distributed with a free-will license.
// Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
// SHT31
// This code is designed to work with the SHT31_I2CS I2C Mini Module available from ControlEverything.com.
// https://www.controleverything.com/content/Humidity?sku=SHT31_I2CS#tabs-0-product_tabset-2
#include <Wire.h>
// SHT31 I2C address is 0x44(68)
#define Addr 0x44
void setup()
{
// Initialise I2C communication as MASTER
Wire.begin();
// Initialise serial communication, set baud rate = 9600
Serial.begin(9600);
delay(300);
}
void loop()
{
unsigned int data[6];
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Send 16-bit command byte
Wire.write(0x2C);
Wire.write(0x06);
// Stop I2C transmission
Wire.endTransmission();
delay(300);
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Stop I2C Transmission
Wire.endTransmission();
// Request 6 bytes of data
Wire.requestFrom(Addr, 6);
// Read 6 bytes of data
// temp msb, temp lsb, temp crc, hum msb, hum lsb, hum crc
if (Wire.available() == 6)
{
data[0] = Wire.read();
data[1] = Wire.read();
data[2] = Wire.read();
data[3] = Wire.read();
data[4] = Wire.read();
data[5] = Wire.read();
}
// Convert the data
int temp = (data[0] * 256) + data[1];
float cTemp = -45.0 + (175.0 * temp / 65535.0);
float fTemp = (cTemp * 1.8) + 32.0;
float humidity = (100.0 * ((data[3] * 256.0) + data[4])) / 65535.0;
// Output data to serial monitor
Serial.print("Temperature in Celsius :");
Serial.print(cTemp);
Serial.println(" C");
Serial.print("Temperature in Fahrenheit :");
Serial.print(fTemp);
Serial.println(" F");
Serial.print("Relative Humidity :");
Serial.print(humidity);
Serial.println(" %RH");
delay(500);
}
ok I have no idea what im doing now! the error has gone but i cant see how to get it to display the second sensors info
You are putting the 6 bytes of requested data from the two different sensors in the same array data[6] and the values from the second reading are overwriting the first.
You are only converting the data from the second reading given how you are executing the convert the data code only once per loop.
You also have some extra brackets.
Think this through a bit more, and see what you can come up with. You are close.
You know how to correctly fill one array and print out the data from that array. Declare a second array data2[6] and fill it using the same wire commands as before but using addr2.
Convert and print the data from the two different arrays holding the data.
There are more memory efficient ways to do this, but try the simple "duplicate everthing" to get going.
Yes, good job. In my earlier advice I was focused on the main barriers operation as you wanted. Now you can work to refine the code.
As Paul says, this next piece of code is not doing anything useful, but it is pretty harmless. Still it would be better to remove it. I didn't really notice it and was basing my reply on the fact that you received one set of data correctly.
The second thing that Paul points out is this, and it opens up a major topic for consideration
if (Wire.available() == 6)
{
It turns out that Wire.available() returns the number of bytes requested. So checking for 6 doesn't ensure that they were sent. See this discussion in Nick Gammon's tutorial on the i2c bus. The entire article is worth your time.
You need to decide how important the data is, and how robust the communication needs to be. You can be expanding your code to use start and stop markers, crc checking, and data rejection of wild numbers.
You won't be the first Arduino user to blindly accept whatever the assemblage of Wire.read() values produces, but you should think about the issue. If there were issues of safety or equipment damage dependent, or paying customer satisfaction dependent upon the values you read, you would need to address the error situation.
