ESP8266 Community Forum

- Wed Jul 06, 2016 11:16 pm #50328 Hi All,

I am using the ESP8266 Series 7 Module shown in the image below. Unfortunately I am having some trouble caused by the default pin state of GPIO12 during boot loader mode. It appears that in boot loader mode the state of GPIO12 is high impedance with a weak internal pullup (correct me if I’m wrong), the problem with this is having GPIO pin pulled high will enable a part of my circuit which interferes with the UART serial lines (RX and TX) causing the programming to fail.
Is there a way to set the pin state of GPIO12 during boot loader mode to set it to high impedance without pull ups?
Also does anyone have any information on all GPIO states in boot loader mode?

- Thu Jul 07, 2016 11:19 am #50359 Why simply add a 10K pulldown on this GPIO to prevent your external circuit to be enabled ?

- Thu Jul 07, 2016 11:30 am #50361 I currently do have an extremely weak pull down at this pin. however it in not strong enough to overcome the weak pull up and end up acting as a voltage divider.

My original concern with a 10K pull down is my circuit needed to operate on extreme low quiescent current to meat our clients battery requirements. although now that i think about it if it being pulled up by a weak pullup (high value resistor) then pulling it down with 10K will not really add much current.I think in my mind i originally calculated the quiescent current if one side of the pull down was connected directly to 3.3V and the other side to ground which is not the case when there is a weak pullup active.

- Thu Jul 07, 2016 2:08 pm #50370 Effectively, the input leakage itself is about 50uA, and with internal pullup fighting with external pulldown, the current is limitted by the sum of both.
The only time where current will be higher is when GPIO is turn as Output HIGH.