After a few years I started working with an ESP-01 again. But after so many years I forgot the exact parameters of module I have and was using default settings. For hours I couldn’t flash anything to it. Everytime flashing failed with one error or other. The most occurring errors are :

1. Invalid (unsupported) command 0x8 
2. Invalid head of packet (0x00)
3. Invalid head of packet (0x0f)

The above problems can be due to two reasons mainly

1. Wrong settings
2. The module needs to be RESET to get the flashing started. The timing of pressing reset and time of holding it down is important. The RESET needs to be done after the Arduino IDE starts the flashing (…. progress bar). And the RESET will have to be hold low for  1 – 2 seconds.
3. Inadequate power supply

Though many suggested that these errors are due to incompatible signal levels between Arduino and ESP but in my case it was not. Previously also I had successfully flashed without logic level converters.

Proper parameters for ESP-01. Please note Flash mode will need to be set as per the chip. Newer ones need DOUT specifically. Whereas the old ones work with both QIO and DOUT. Burning with wrong mode will result in a successful upload but the code will not work.