Go Down

Topic: storing Serial bytes to a float variable (Read 823 times) previous topic - next topic


Oct 15, 2011, 11:04 am Last Edit: Oct 15, 2011, 11:12 am by giantsfan3 Reason: 1
I'm reading values from a sensor, coming in as serial data.

The values come in multiple Serial bytes as follows:
For example a sensor reading of 2.16 comes in as the following four bytes: '2', '.', '1', '6'
Fairly simple, and it's been easy to print those 4 bytes out individually just using mySoftSerial.read() for each incoming byte; and then Serial.print(...) the 4 bytes to the terminal.

However, I would like to STORE altogether the four separate incoming Serial bytes of the value "2.16"... specifically, I want to store into one float variable so I can do arithmetic with it.
What would be an effective way to accomplish that?

Seems like a common thing to do, but I haven't come across any simple method.

[sidenote: I tried the approach discussed in a past thread, of using a union that has a float and a byte array, but that didn't solve the problem here because it appears the incoming data also has to have been sent out from a byte array originating from a union, which is not the case here]


If you store the characters received from the sensor in a character array, and append a null character when you have finished receiving characters, then you can use the atof() function to convert them to a double, and thence to a float.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.


On the Arduino I believe double and float are the same thing, an IEEE 32 bit float.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


That worked successfully. Thanks dc42. Why the null character at the end by the way?

And indeed arduino's implementation of double and of float appear to be identical:
"The double implementation on the Arduino is currently exactly the same as the float, with no gain in precision." [http://arduino.cc/en/Reference/Double]


The null makes it a C string, and shows the string routines like atof or atoi where the string ends.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131