title: Cannot program ESP8266
body: <p>Blue led is blinking after powering up the module, the red one stays on, I can even connect to it via wifi. But I cannot program it. I tried Arduino IDE, different firmware flashers (Like NodeMCU, XTCOM). I'm using Arduino Mega.</p>
  
  <p>Here's my initial setup:</p>
  
  <pre><code>VCC - 3.3 V on Arduino
  RST - nothing
  CH_PD - 3.3 V on Arduino
  TX - RX on Arduino (TX is transmitting data to RX, so I don't need a voltage divider, right?)
  RX - voltage divider (R1 = 10K, R2 = 20K) - TX on Arduino
  GPIO0 - GND on Arduino
  GPIO2 - nothing
  GND - GND on Arduino
  </code></pre>
  
  <p>Then I tried uploading a sketch from the Arduino IDE and got the following error:</p>
  
  <pre><code>warning: espcomm_sync failed 
  error: espcomm_open failed
  </code></pre>
  
  <p>After trying different IDEs, programmers, serial port I tried firmware flashers to at least see if I can communicate with it. NodeMCU for example just
  showed "Waiting MAC" with GPIO0 to ground and without.</p>
  
  <p>I also tried connecting TX to TX and RX to RX but got the same results. Tried connecting RX through a voltage divider as well. </p>
  
  <p>With this setup the blue led was constantly on. I remembered reading somewhere that that could happen due to insufficient power supply, 
  so I also tried connecting both pins without the voltage dividers (the blue led is still blinking after the power up so hopefully I didn't burn them).
  I also tried connecting GPIO0 to 3.3V and not connecting it to anything at all, connecting RST to 3.3V, connecting GPIO2 to ground as well.
  On Mega there are 4 sets of TX and RX pins, so I tried them all out TX/RX0,1,2 and 3.</p>
  
  <p>Still no idea what's going on :(</p>