ESP8266 Community Forum

I've done a few searches so bear with me if it's been covered already.

I have a circuit mapped out on a breadboard for adding wifi to an espresso machine via esp8266-01 and using the st_anything GitHub repos.

My problem is that the espresso machine uses a momentary button to trigger the machine on with a 5V pulse, which is easy enough. But the esp8266-01 module (or maybe other versions too) give off a short pulse on the gpio pins right when you first power up the module. This would be ok too but I don't want the machine to power up every time I plug it in or have a power outage when i'm not at home.

Is there a way to cut out that first little blip of power using a hardware solution? Some sort of filter that only gives an output if the gpio is on for 3 seconds or so? Or some other solution?

Thanks in advance.

Use GPIO4 or GPIO5. They do not have any action when the ESP8266 turns on. There are other hardware methods but this would be easiest. You should have a pull-down resistor included to give the line a defined state before it is initialized.

Other options is to use one of the port pins that have internal pull-up enabled on turn on to drive a p-channel mosfet. Low being On. The mosfet inverts the signal and you get a high out. (3.3v)

Opto-couplers can be used.

Are you intending to use the esp-01 module (8 pin header)? They have very limited access to the GPIO pins just GPIO00 and GPIO02, compared with either dev boards or esp-12 modules. I don't use esp-01 for that reason.

I think as Rudy suggested if you make the trigger active low by inverting with a buffer (mosfet or bjt) which you will probably need to get 5V pulse anyway then you can avoid the problem by using a pull up to 3.3V on the pin and ensuring you set the data output high before you set the pinMode.

btidey wrote:.. set the data output high before you set the pinMode.

Yes, always set the output state before enabling the port for output.