Hi, first I bought 1 pcs MOD-WIFI-ESP8266. There was no problem with downloading and installing NodeMCU Firmware. Module works good with ESP8266 LuaLoader (v0.87). Next I bought 2 pcs MOD-WIFI-ESP8266-DEV. Installing firmware - ok. But there is no communication with LuaLoader. Pin GPIO0 is high. All modules use UEXT connector. I only use pins 1,2,3,4. Has anybody similar problem?
No problems yet and I've used several of these. Pin 1 = 3,3V. Pin 2 = GND, Pin 3 goes to Rx Pin of USB-TTL converter, Pin 4 goes to Tx Pin of USB-TTL converter. GPIO0, GPIO2 and MTDO are connected on the board through resistors to Vdd or Vss as required, so you don't need to bother with any other pins than 1-4 at first.
If you can load, then serial works. After loading, you need to reset the chip with GPIO0 high (i.e. pull pin RST_B low or remove power and then repower the chip).
How are you communicating with the chip after it is programmed and reset? ESPlorer?
I use LuaLoader or ESPlorer. With MOD-WIFI-ESP8266 there is no problem. With MOD-WIFI-ESP8266-DEV can not communicate. I did all you have written. BTW I think that Pin 3 (UETX) goes to Tx Pin of USB-TTL converter and Pin 4 (UETX) goes to Rx Pin of USB-TTL converter i.e. Rx->Tx and Tx->Rx