void setup() {
    // $ stty -F /dev/ttyUSB0 | grep speed
    Serial.begin(115200);
    // A0 for compatibility with analog configuration
    pinMode(A0, INPUT);
}

void loop() {
    // effective sample rate measured with "Probe Rate" block
    // $ tail --follow /dev/ttyUSB0 | od --format=u1 --width=1
    Serial.write(digitalRead(A0));
}