ESP8266 Community Forum

- Sat Mar 03, 2018 10:04 am #74336 Hello,

I bought 2 of these from Alibaba. One of these seems to work, but the other one does not.

Both wifi modules are OK, but the other relay module does not. It flashes the led continuously. Wifi module comes up, but command to use relay does not do anything.

Relay coil gives slight noise while led flashes. I suppose it does try to switch.

I found somewhere information that one resistor should be removed. I did it. Led still flashes, but now relay switches as it flashes. Commands do nothing.

Has anyone else had this kind of trouble with it? What would be next thing to try?

- Sun Mar 04, 2018 6:58 am #74355 Something more about the above things.

Is it possible to backup STC15 microcontroller firmware?

There seems to be several means to update it, but I would like to read firmware from properly working devise and try to put it in the other not so well working one.

- Sun Mar 04, 2018 8:29 am #74357 Roflmao...look back a page bottom 2 posts. That is exactly what I was commenting on above. Hope u still have that resistor

- Mon Mar 05, 2018 5:33 am #74367

Roflmao...look back a page bottom 2 posts. That is exactly what I was commenting on above. Hope u still have that resistor

Well - I might try to switch the resistors first to see what happens then, but I have a bad feeling, my case is different. It sounds like the MCU is in a boot loop causing the led to flash every time it boots again. This happens 2 or 3 times every second.

I did try to make serial connection in it, but I don't know if this imminent boot loop prevents it.

I suppose the MCU can't be flashed without powering it. Or can it?