SunFounder 3in1 Kit - How to Re-Burn the Firmware for ESP8266 Module

SunFounder 3in1 Kit
7.2 How to re-burn the firmware for ESP8266 module?
7.2.1 Re-brun the Firmware with R4
1. Build the circuit
Connect ESP8266 and Arduino UNO R4 board.
2. Upload the Following Code to R4
void setup() {
Serial.begin(115200);
Serial1.begin(115200);
}
void loop() {
if (Serial.available()) { // If anything comes in Serial (USB),
Serial1.write(Serial.read()); // read it and send it out Serial1 (pins 0 & 1)
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7.2. How to re-burn the firmware for ESP8266 module? 335