Drop alpha character from serial input

Question

I receive strings over the serial port like so:

VLT=53.0, AMP=-30.2, AHR=-10, SOC=98, TMP=136, STS=192

I want to reduce the use of string functions with the idea of dropping all non-digits, keeping numbers dot and comma, to get this:

53.0,-30.2,-10,98,136,192

in an array and simple read [0], [1], etc.

Regular expressions would be idea, but do not exist like in PERL. Any hint would be much appreciated.

Relevant code used:

 char inByte = SerialPortOne.read(); // read byte
 strRecordIn.concat(inByte); // add byte to receive buffer
 for (int i = 0; i <= 3; i++) { // VLT, AMP, AHR, SOC
 strWord = getValue(strRecordIn, ',', i); // get data item from RecordIn array
 strWord.remove(0, 4); // remove field identifier (1st 3 char plus =)
 strRecordOut += ','; // add delimiter
 strRecordOut += strWord; // add value
 strWord = ""; // reset strWord
 }

Ideally:

 char inByte = SerialPortOne.read(); // read byte
 if (inByte = [%d.,]+) {
 strRecordIn.concat(inByte); // add byte to receive buffer
 }

Answer 1

If you just want to remove the letters:

#include <ctype.h>
char inByte = SerialPortOne.read(); // read byte
if (!isalpha(inByte)) { // not letter
 strRecordIn.concat(inByte); // add byte to receive buffer
}

Or you may test it for isdigit() and explicitly compare to ',' and '.':

if (isdigit(inByte) || inByte == '.' || inByte == ',') {
 strRecordIn.concat(inByte); // add byte to receive buffer
}

C.f. the documentation of <ctype.h>.

• MaxG: Brilliant! I got lots to learn in this Arduino environment. Thank you!
• Edgar Bonet: @MaxG: Well, in this case it's standard C, not specific to Arduino.