This message indicates issue with uploading ESP module over a serialconnection. There are couple of possible causes, that depend on the typeof module, if you use separate USB to serial converter, what parametersare selected for upload, etc. As result there is no single answer on theroot cause. To find it out you may need to complete couple oftroubleshooting steps.
Note: If you are just starting with ESP, to reduce potential issueswith uploading, select ESP board with integrated USB to serialconverter. This will considerably reduce number of user dependedfactors or configuration settings that influence upload process.
Example boards with USB to serial converter build in, that will makeyour initial project development easier, are shown below.
Example boards with integrated USB to serial converter¶
If you are using a Generic ESP8266 module, separate USB to serialconverter and connect them by yourself, please make sure you have thefollowing three things right: 1. Module is provided with enough power,2. GPIO0, GPIO15 and CH_PD are connected using pull up / pull downresistors, 3. Module is put into boot loader mode.
For specific details please refer to section on Generic ESP8266 module.Example modules without USB to serial converter on board are shown below.
Example ESP8266 modules without USB to serial converter¶
In order to troubleshoot “espcomm_sync failed” error, please proceedstep by step through the checklist below. This list is organizedstarting with most common and simple to more complex issues.
Start with reading exact message displayed in debug window of ArduinoIDE. In many cases it provides direct information where the issue is.
“espcomm_open failed” error¶
For instance message above suggests that Arduino IDE is unable to open aserial port COM3. Check if you have selected port where your module isconnected to.
Serial port selection¶
If a module is connected to the serial port but not responding as avalid ESP8266 device, the message will read slightly different (seebelow). If you have other modules connected to your PC, make surethat you are uploading code to ESP8266 and not to e.g. Arduino UNO.
Serial port selection¶
To have your PC talking to ESP, select exact ESP type in upload menu.If selection is incorrect then the upload may fail.
Basing on selected board type, Arduino IDE will apply specific “resetmethod” to enter the board into boot loading mode. Reset methods areboard specific. Some boards do not have the h/w in place to supportreset by Arduino IDE. If this is the case, you need to enter such boardinto boot loading mode manually.
Upload may be also failing due to too high speed. If you have long orpoor quality USB cable, try reducing selection under Upload Speed.