Troubles connecting Arduino Leonardo with ESP8266

Hello, to connect my Arduino Leonardo to a W-LAN, I bought a ESP8266 (ESP-01 or also referred to as V090) Module. I hooked the ESP8266 to an external power source as it requires up to 200mA, and as far as I know, the Arduino only offers 50mA on it's 3.3V out. The external Power source offers 5.2V and 2250mA. I used a voltage devider to get 3.3V (3.23V to be precise). I hooked the external power source to the VCC and CH_PD pins of the ESP8266 as described in many tutorials. I also connected the UTXD (TX) pin of the ESP8266 to the RX1 of my Arduino. To get a 3.3V signal on the URXD (RX) pin of the ESP8266, I put another voltage devider (1k/2k) between the TX1 of the Arduino and the URXD (RX) pin of the ESP8266.

I tried to send/recieve commands to the ESP8266 module using the following sketch:

void setup() {
  while (!Serial); // wait for serial port to connect. Needed for Leonardo only
  Serial.println("Serial ready");
  Serial.println("Serial 1 ready");

void loop() {
  if (Serial.available()) {
    String str = Serial.readStringUntil('\n');
    Serial.println("You sent: " + str);
  if (Serial1.available()) {
    char chr =;
    if(chr != 0) Serial.print(chr);

When I connect everything, the blue LED of the ESP8266 starts flashing rapidly, but all I get on the serial monitor is jibberish. I also tried different baud rates for the Serial1 connection.

So can anyone help me and explain what I might have done wrong? And please excuse me if I did something stupid, but I'm new to Arduino programming.

Thank you in advance!

After I got some replies on the german forum, I replaced the external power supply with voltage divider with a matching 3.3V power supply. I also connected GND of Arduino and ESP8266.

This is my current Setup: |500x236 ("Netzteil" in the image means "power supply". Full size Image:

Now I get no signal from ESP8266 and the blue LED stays off. Does anyone have an idea what could be wrong?

I solved my problem. The Setup and Program sketch above work. I just made a mistake at soldering :blush: It works at a baud rate of 9600.