How to work around blinking display when with SPI tft display

Other Hardware Displays
1

I am currently playing with using a spi tft display for a little project that displays some data.

I'm using the adafruit libraries as

#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7735.h> // Hardware-specific library

I've wired it up for fast display but I find I have to some how erase the previous data displayed before updating it. at first I just did a clear screen with

tft.fillScreen(ST7735_BLACK);

before showing new data (text rotated)
but the blinking was awful

then I tried just drawing a black rectange over the area of the text with

tft.fillRect(0, 30, 200, 60, ST7735_BLACK);

and it's a tiny bit better. There must be a better way. Can't help but wonder if it's the overall structure of the code that is my real issue.

here's the full code

#define cs   10
#define dc   9
#define rst  8  // you can also connect this to the Arduino reset

#define TRIGGER_PIN  7  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     6  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 600 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7735.h> // Hardware-specific library
#include <SPI.h>
#include <NewPing.h>
//#include <stdio.h>

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); 

#if defined(__SAM3X8E__)
    #undef __FlashStringHelper::F(string_literal)
    #define F(string_literal) string_literal
#endif

Adafruit_ST7735 tft = Adafruit_ST7735(cs, dc, rst);

void setup(void){
   Serial.begin(115200);
  tft.initR(INITR_BLACKTAB);
  tft.setTextWrap(false); // Allow text to run off right edge
  tft.fillScreen(ST7735_BLACK);
  tft.setRotation(1);
  
}
void loop(void) {
  
 int totalPing=0;                      // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
  unsigned int uS;
 for (int i=0;i<=4;i++){
  uS = sonar.ping(); // Send ping, get ping time in microseconds (uS).
  Serial.print("reading");
  Serial.print(i);
  Serial.print(":");
  Serial.println(uS/US_ROUNDTRIP_IN);
  totalPing=totalPing+uS;
  delay(30);
  }
  tft.fillRect(0, 30, 200, 60, ST7735_BLACK);
  uS=totalPing/5;
  int r;
  int f;
  int i;
  int remainder;
   
   tft.setTextSize(1);
   tft.setCursor(0,100);
   tft.print("Rangefinder V 0.1");
   tft.setTextColor(ST7735_YELLOW);
   tft.setTextSize(6);
   tft.setCursor(0, 30);
   r=uS/US_ROUNDTRIP_IN;
   Serial.println(r);
   remainder=r%12;
   f=(r-remainder)/12;
  tft.print(f); // Convert ping time to distance in cm and print result (0 = outside set distance range)
  tft.print(":");
  tft.print(remainder);
  //delay(50);
  
}