ESP8266 Community Forum

- Fri Feb 25, 2022 5:47 am #93762 Ohms law should help here. If there is 1.4V across the resistor then you know the current going through that resistor. That current has to go somewhere. What value pull up are you using?

At boot time when the pins are being measured for boot mode then GPIO is set to as an input (with an internal pull up of about 35K so the current can't be flowing back into the ESP if it is working.

Do you have anything else connected to GPI0?

It is possible that GPIO is damaged but I would think it more likely that you have something else connected.

- Fri Feb 25, 2022 7:40 am #93764 Pull up value is 1k.

There is nothing else connected. Just a straight pullup, no other circuitry, these GPIOs are not used.
A 1.4V drop over 1k therefore result into 1.4mA.

- Sun Feb 27, 2022 9:34 am #93776 Have you treated GPIO15 correctly?

- Mon Feb 28, 2022 7:05 am #93780

Pull up value is 1k.

There is nothing else connected. Just a straight pullup, no other circuitry, these GPIOs are not used.
A 1.4V drop over 1k therefore result into 1.4mA.

That would seem to indicate a bust pin on the module.

I would, however, try a couple of things.

1) Remove all connections to GPIO0 including the external pull up resistor. An ESP8266 will boot OK even with no extra pull up on this as the internal pull up will work OK. The reason for an external one is just to provide some extra resilience against noise being coupled in but this will not be an issue if there is nothing else connected. By removing all connections you ensure there is no other inadvertent path for current. This does actually also apply to GPIO2, but GPIO15 definitely does need an external pull down for a successful boot.

2) If possible use a scope to see how the voltage on the pin behaves during the period after reset. If it is a solid 1.9V all through this then that is an extra indication this is bust.