Hervé Tavernier asked 5 years ago
In the “Esp32 MQTT – Publish an subscribe with Arduino IDE” project the float BME sensorreadings are converted to a char aray so they can be published as esp/reading topics.
For this conversion dtostrf(reading,1,2 readingString) is used.
Can you please explain the parameter 1 in this expression?
Thank you very much.
i am an absolute ESP32 – MQTT – beginner.
Hervé Tavernier Belgium
Sara Santos Staff answered 5 years ago
Hi Herve.
Here is the syntax of the stostrf() function
dtostrf(floatvar, StringLengthIncDecimalPoint, numVarsAfterDecimal, charbuf);
where
- floatvar – float variable
- StringLengthIncDecimalPoint – this is the minimum length of the string that will be created including the point
- numVarsAfterDecimal: the number of digits after the decimal point
- charbuf: the array to store the results
I think you may be confused because the length is 1, which is smaller than the number of decimal points.
1 is the minimal length, that means that it will work even if the string is bigger than that.
For example, if you define a minimum length of 8, you’ll get 8 characters, even if your string is smaller than that. It will add white spaces to make it 8 characters long. So, if you set it to 1, you guarantee that you won’t get white spaces.
I hope this is clear.
Regards,
Sara
Hervé Tavernier answered 5 years ago
Hello Sara
I am very happy with your quick and clear answer to my question.
The parameter 1 now has no more secrets for me!
Thank you very much!
Hervé
P.S. Apologize for my poor English. My native language is Dutch
Sara Santos Staff answered 5 years ago
Great.
No need to apologize. My native language is Portuguese. My English is not perfect either.
I’ll close this question.
If you need further help you just need to open a new question in our forum.
Regards,
Sara