I am trying to use a Sensirion flow sensor (uses I2C). It works perfectly with an Uno R3 but gives an error with the Uno R4 WiFi. This is the sensor: Smart sensor solutions I've tried two versions of the code. One is a script I received directly from them located here: https://github.com/Sensirio…

[image] faaizenam: Create a 1.8Kohm 'short' between A4 and 3V3 Short? A short circuit has no resistance so this makes no sense. Here is what I did when I wanted to drive a 3V3 device from a R4 Arduino. [Pull_up resistors] [image] faaizenam: B. Attach a 1.8Kohm between A4 and the senso…

The R4 board does not have any pull up resistors on it try adding some. I2C will not work without them on the R4.

Thanks for the response! At this link, they reference the connections: [image] GitHub - Sensirion/arduino-i2c-sf06-lf: Sensirion Liquid Flow I2c drivers for... Sensirion Liquid Flow I2c drivers for Arduino. Contribute to Sensirion/arduino-i2c-sf06-lf development by creating an account o…

[image] faaizenam: What are pull up resistors? Resistors that are used to make the normal, un-driven state of the bus a logic high. [image] faaizenam: How do I determine the resistance needed? You require a current of 2 to 4mA, so the calculation is always the same depending on the vo…

Thank you. I assume I add this 1.8K resistance in the 3V3 line between the sensor and the Arduino? I was looking at this conversation here which seems to suggest in the R4 we can only use the 5V line? Problem? using Arduino Uno R4 Minima and I2C - #9 by geirandersen

[image] faaizenam: I assume I add this 1.8K resistance in the 3V3 line between the sensor and the Arduino? No. A pull up resistor is added between the I2C line A4 and the bus drive voltage. There should be another on A5 and the bus drive voltage. [image] faaizenam: I was looking at this …

I'm looking into how pull up resistors are connected (new to this) based on what you've described is it: A. Create a 1.8Kohm 'short' between A4 and 3V3 and a separate one between A5 and 3V3? B. Attach a 1.8Kohm between A4 and the sensor SDA pin and a separate one between A5 and sensor SCL pin?

Thank you! I'll let you know once this works!

[image] Grumpy_Mike: pull up resistor actually, the R4 does have internal pull up resistors. Simply modify the blink example to void loop() { pinMode(A5, INPUT_PULLUP); // turn the LED on (HIGH is the voltage level) delay(1000); // wait for a second pinMode(A5,…

[image] Klausj: actually, the R4 does have internal pull up resistors. Simply modify the blink example to Yes BUT only to 5V. To run the bus at any other voltage, like 3V3 then you need pull up resistors to that voltage. [image] Klausj: But you are right: the internal resistor is way to…

Finally got a chance to get back into lab. The 1K8 pullup resistors worked! Thanks for your help Grumpy_Mike!

I2C sensor working on Uno R3, not R4 WiFi

Official Hardware UNO Family UNO R4 WiFi

faaizenam October 20, 2023, 4:40pm 3

Thanks for the response!

At this link, they reference the connections:

What are pull up resistors? How do I determine the resistance needed?

Thanks

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I2C sensor working on Uno R3, not R4 WiFi

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