Drop alpha character from serial input
If you just want to remove the letters:



#include &lt;ctype.h&gt;

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
&lt;ctype.h&gt;.