Error While Printing on I2C OLED Display in Arduino - arduino

Question

#define OLED_RESET -1
Adafruit_SSD1306 display(OLED_RESET);
char buff[10]="hola";
char buff2[10]="";
int cnt=0;
int b=0;
int alpha=1;
void setup()
{
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
display.clearDisplay();
display.setTextColor(WHITE);
Serial.begin(9600);
}
void loop()
{
while (Serial.available()) {
char a = Serial.read();
buff[cnt++] = a;
alpha=1;
}
if(alpha==1){
display.clearDisplay();
display.setCursor(0,0);
display.setTextSize(1);
display.println(buff);
display.display();
cnt=0;
alpha=0;
}
}
it prints first incoming string at place where i wat but when it receives second string it shifts to new line mean changes y position and after that it does not print any thing on display. Could any one can tell me the error i have made here.

Answer 1

The string you are building from the received characters isn't null-terminated when you print it. Add
buff[cnt++] = '\0';
before calling println.

Answer 2

this code does the same thing as yours but with strings(I thing it is more useful than char arrays) Don't forget to replace "MaxLength" in line 15 with your own number
#define OLED_RESET -1
Adafruit_SSD1306 display(OLED_RESET);
String input;
void setup() {
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
display.clearDisplay();
display.setTextColor(WHITE);
Serial.begin(9600);
}
void loop() {
if(Serial.available() > 0){ //if input available
input = Serial.readString(); //Serial input to string
if(input.length() > MaxLength) input = ""; // check if string isn't too long, replace 20 with your value
display.clearDisplay();
display.setCursor(0,0);
display.setTextSize(1);
display.print(input); //I removed "ln" from println to not send \n at end of string
display.display();
}
}
I hope this will work