I have been unsuccessful in establishing any I2C communication with my Atlas Scientific EZO CO2 sensor. The sensor works fine in UART mode, but when I try to use I2C protocol I can't get past the Wire.beginTransmission function.
Having struggled with this for a few days, I have abandoned trying to get the code from the manufacturer working, and focused on simply identifying the sensor with I2C_scanner from the Arduino IDE.
Below is the i2c scanner code, I have simply added some serialprintlines to troubleshoot, and as I mentioned, I don't get anything past "address scanning" + "1" on the serial monitor. Which leads me to believe it's something with the way I'm wiring it, despite having done so exactly as depicted in the below Atlas Scientific Sample Code link. I've also tried attaching a 4.7 kohm resistors between 5V and the clock and data pins, and I've tried using the A4 (SDA) and A5(SCL) as well as the SCA and SDA pins (pins 16 and 17).
Another thing to mention is that I've tried to wire this to an MKR Wifi 1010, and anytime I connect the SCA and SCL pins to the sensor the chrg battery light starts to flicker.
Thank you in advance and please let me know what additional info I need to share.
#include <Wire.h>
void setup() {
Wire.begin();
Serial.begin(9600);
while (!Serial); // Leonardo: wait for Serial Monitor
Serial.println("\nI2C Scanner");
}
void loop() {
int nDevices = 0;
Serial.println("Scanning...");
for (byte address = 1; address < 127; ++address) {
// The i2c_scanner uses the return value of
// the Wire.endTransmission to see if
// a device did acknowledge to the address.
Serial.print("address scanning "); //debug
Serial.println(address); //debug
Wire.beginTransmission(address);
byte error = Wire.endTransmission();
Serial.println("if statement for that address"); //debug
if (error == 0) {
Serial.print("I2C device found at address 0x");
if (address < 16) {
Serial.print("0");
}
Serial.print(address, HEX);
Serial.println(" !");
++nDevices;
} else if (error == 4) {
Serial.print("Unknown error at address 0x");
if (address < 16) {
Serial.print("0");
}
Serial.println(address, HEX);
}
}
if (nDevices == 0) {
Serial.println("No I2C devices found\n");
} else {
Serial.println("done\n");
}
delay(5000); // Wait 5 seconds for next scan
}
Most probably you have to add pullup resistors (5-10k to 5V) to SCL and SDA. Such resistors are not present on an Uno board and usually reside on sensor breakout boards.
SDA is on A4 and SCL on A5, so no I don't believe I have.
the GND from Arduino is connected to the - side of the power bus
I have another probe that is very similar to this, it's a Humidity probe from Atlas Scientific as-well. Again that one worked well with UART, but when I switch it to I2C mode and connect data and clock, the probe will behave weird and tends to switch back UART mode. I will try it again with the 4.7k resistors.
I did, by shorting green and blue. When I am in UART mode I can switch it via command from serial monitor, however once in i2C I am no longer able to send or read anything it seems.
I believe so, the light is solid blue which means it's I2C. I say I think so because in UART mode the light blinks green when operating properly, as opposed to the solid blue that I have. However I can see the IR light source from the probe end blinking, which leads me to believe that the sensor is sending readings.
I don't understand the question. You should measure the same voltage from GND to SCL, everywhere that SCL is connected, including the sensor.
Disconnect everything from the Arduino, and run the I2C scanner program, while measuring the voltages from GND to SDA (or A4) and SCL (or A5). It should be 4.8 to 5V on both. If not, the Arduino is defective.
To avoid confusion due to transient voltage changes on SDA and SCL you could try the following minimized program, which sets up the connection but does not use it.
#include <Wire.h>
void setup() {
Wire.begin();
Serial.begin(9600);
while (!Serial); // Leonardo: wait for Serial Monitor
Serial.println("\nI2C Scanner");
}
void loop() {}
Ok thank you so much for your help. All this time wasted and I was dealing with a defective Arduino.
So I re-did everything on the MKR board, made sure to put the resistors in this time, which was the only thing I had yet to try. It seems to be working, I'm getting multiple address including the probe I installed.
