int CHA = 2;
int CHB = 3;
int ENA = 4;
char ASCII_cmd;


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);


pinMode(CHA,OUTPUT);
pinMode(CHB,OUTPUT);
pinMode(ENA,OUTPUT);
}

void loop() {
  while (Serial.available() < 1) {
  }
  
  ASCII_cmd=Serial.read();

    
 // If the ASCII command is 65 ('a') then do a memory dump to the PC
 if (ASCII_cmd == 'C') {
 digitalWrite(CHA,HIGH);
 digitalWrite(CHB,LOW);
 digitalWrite(ENA,HIGH);
 }

  // If the ASCII command is 65 ('a') then do a memory dump to the PC
 if (ASCII_cmd == 'D') {
 digitalWrite(CHA,LOW);
 digitalWrite(CHB,HIGH);
 digitalWrite(ENA,HIGH);
 }
 
 }