11 TROUBLESHOOTING
If you flashed a used ESP, sometimes the esp module does not want to connect to wifi. In the config portal it seems to connect and the blue led blinks 3 times but it still didn't connect. The ESP is not saving the credentials, this is because there is already a filesystem on the ESP with a different format. In general, if you cleanup the memory of your ESP (e.g. flash something on it with the option "erase flash and wifi settings", ( see the picture below ) and then reflash the ESP-ECU binary, it will work.
Another trick: Watch the serial monitor while connecting and if you see "Youpy, connected!" push the resetbutton. The Esp wil now reboot and connect, showing its IP.
If not, as a workaround, you can first flash another program, (with Flash Size configuration 4MB(FS:2MB OTA:~1019KB)) for example a basic web server, with the wifi credentials hardcoded. If this connects, you can flash the ESP-ECU. This will then connect with the already existing credentials. The admin password now is probably 0000. You can change this by starting the AP via the menu.
If you can't get the coodinator up, there are several possibilities. The wiring isn't correct, the firmware on the cc25xx isn't right, The module is defective. Some things you can determine by doing a loopbacktest. If this doesn't work you should examen the wiring and you can ensure that the serial port on your esp is working (please see next chapter UART).
If you want to be sure that the serial port on your ESP board is working, you can connect Rx and Tx with a dupont wire. Now open the console, type 10;diag, diagNose should be set to 1. Now type 10;zbt=12AB24. Your message (converted to a zigbee message) will be echo-ed back.