// put your setup code here, to run once:
#include <MD_Parola.h>
#include <MD_MAX72xx.h>

#define CS01  10
#define DIN  11
#define CLK  13
#define CS02  7
#define CS03  5
#define PINA 12
#define PINB 8
#define PINC 9
#define RTN 6 //return
#define SFT 4 //shift
#define BS 3
#define HARDWARE_TYPE MD_MAX72XX::PAROLA_HW
#define MAX_DEVICES  8

MD_Parola P = MD_Parola(HARDWARE_TYPE, CS01, MAX_DEVICES);  
MD_Parola Q = MD_Parola(HARDWARE_TYPE, CS02, MAX_DEVICES);
MD_Parola R = MD_Parola(HARDWARE_TYPE, CS03, MAX_DEVICES);

String a = "_";
String c = " ";
String b = ">";
uint8_t n = 0;
uint8_t m = 0;
uint8_t l = 0;

void upperlower() {if(m == 1) c.toUpperCase(); back1(); b = b + c + a; m = 0; delay(100); return(b);}
void back1() {l = b.length(); l = l - 1; b.remove(l); return(b);}
void back2() {l = b.length(); l = l - 2; b.remove(l); return(b);}

void setup() {
  P.begin();
  Q.begin();
  R.begin();

  pinMode(PINA, INPUT_PULLUP);
  pinMode(PINB , INPUT_PULLUP);
  pinMode(PINC, INPUT_PULLUP);
  pinMode(RTN, INPUT_PULLUP);
  pinMode(SFT, INPUT_PULLUP);
  pinMode(BS, INPUT_PULLUP);
}
void loop() {
  
  if (digitalRead(SFT) == LOW) m = 1; //upper case
  if (digitalRead(PINA) == LOW) {c = "a"; upperlower();}
  if (digitalRead(PINB) == LOW) {c = "b"; upperlower();}
  if (digitalRead(PINC) == LOW) {c = "c"; upperlower();}
  if (digitalRead(BS) == LOW) {back2(); b = b + a; delay(500);}
  if (digitalRead(RTN) == LOW) {n = n + 1; b = ">"; delay(100);}
  if (n == 0) P.print(b);
  if (n == 1) Q.print(b);
  if (n == 2) R.print(b);
  if (n == 3) {n = 0; b = ">";}
}