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>.