inline void send_package(size_t howMany) {
  Serial.write('A');  // start marker
  for (size_t i = 0; i < howMany; i++)  Serial.write('2');  // payload
  Serial.write('Z');  // end marker
}

void setup() {
  Serial.begin(9600);
  for (size_t s = 1024ul; s <= 1024ul * 31; s += 1024ul * 2)  {
    delay(1000);
    send_package(s);
  }
}

void loop() {}