Dart handle characters/strings

main.dart

List<int> hexToUnits(String hexStr, {int combine=2}) {
  hexStr = hexStr.replaceAll(" ", "");
  List<int> hexUnits = [];
  for(int i = 0;i < hexStr.length;i+=combine) {
    hexUnits.add(hexToInt(hexStr.substring(i, i+combine)));
  }
  return hexUnits;
}

int hexToInt(String hex) {
  return int.parse(hex, radix: 16);
}

String intToHex(int i, {int pad=2}) {
  return i.toRadixString(16).padLeft(pad, '0').toUpperCase();
}

void main() {
  List<List<int>> asciiList = [[52], [53, 54]];

  print(asciiList.map((List<int> char) => String.fromCharCodes(char)).join()); // 456
  print(160.toRadixString(16).toUpperCase()); // A0
  print(int.parse("A012", radix: 16)); // 40978
  print("A0 12 13".replaceAll(" ", "")); // A01213
  print("ABC".codeUnits); // [65, 66, 67]
  
  String hexStrs = "7E A1 12 00 50 00 03 7E";
  print(hexToUnits(hexStrs)); // [126, 161, 18, 0, 80, 0, 3, 126]
  
  String hexStr = "7E";
  print(hexToInt(hexStr)); // 126
  
  int hexInt = 75;
  print(intToHex(hexInt)); // 4B

  List<int> cmdList = [126, 161, 18, 0, 179, 126];
  print(cmdList.first); // 126
  print(cmdList.last); // 126
  
  print([126, 161, 18, 0, 80, 0, 3, 126].map((int char) => intToHex(char)).toList().join()); // 7EA112005000037E
}

https://dartpad.dartlang.org/064cca36fb1142ae0edc3ded03b30af9