Whenever I boot up the esp8266 or flash code via usb ,I have to remove vin pin otherwise it does not boot up.

If I remove vin pin then flash and boot up happens and then i am able connect vin with 5 V relay.(using VIN to power up relay) .

I dont understand what it has to do with VIN pin.please suggest.

I am using below pins for eight devices

//relay pin setup for funct
int relayOne = 5;
int relayTwo = 4;
int relayThree = 0;
int relayFour = 2;
int relayFive = 14;
int relaySix = 12;
int relaySeven = 13;
int relayEight = 15;
  • the relay board might be passing 5v to a 3.3v pin via a pullup, i've seen that before on active-low relay modules. Some ESPs might not like 5v. use an n-chan to pull down the relay based on 3.3v from the GPIO – dandavis Dec 11 '18 at 20:24
  • Thanks for the input.Anyway I removed gpio 0 2 15 as it creates problem in boot up.now it’s working fine – vijay vikma Dec 12 '18 at 5:05

IO pins 0, 2 and 15 are boot configuration pins. 15 must be LOW at boot, 2 must not be LOW at boot and 0 determines the flashing mode. For normal run pin 0 must be HIGH. The NodeMcu board has necessary pull-up and pull-down circuits.

You can connect to pins 0, 2 and 15 only devices which don't change the boot state.

  • Thanks much. but I don’t understand that why it is working when vin is not connected to relay vcc.it is not booting up only when vin is connected to relay. Second if I remove device from these 3 pin.which other pins I can use.i have total eight devices to control. Thanks in advance – vijay vikma Dec 10 '18 at 16:58
  • it changes if the relay signal pin pulls up or down a pin – Juraj Dec 10 '18 at 17:29
  • Thanks for the support.I removed gpio 0 2 15 and used some other pins.its working fine. – vijay vikma Dec 12 '18 at 5:06
  • Okay I will do it.i am new to stackexchange .not sure where to do it – vijay vikma Dec 12 '18 at 7:19

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