GPIO15 *driven* high after power-up
Posted: Fri Dec 30, 2016 6:18 amI understand that GPIO15 has to be held low during power-up for both normal operation and flashing via uart. What concerns me is that I'm seeing GPIO15 being actively driven following power-up, with no programs loaded.
To replicate, flash any ESP8266 module with GPIO15 broken-out and connected to 0V via a 1K resistor. I used a master branch build from frightanic.com with modules: bit,file,gpio,net,node,tmr,uart,wifi built on: 2016-12-26 11:44 powered by Lua 5.1.4 on SDK 1.5.4.1(39cb9a32)
With no init.lua present, on power-up, I find that 3.3V is present across the resistor, i.e. 3.3mA so it's not a weak pull-up on a GPIO configured as input.
Many projects I've seen (and some ESP01 modules) have GPIO15 hard-wired to 0V which would cause excessive current to flow out of the device so it would seem to be important to understand what's going on.
To replicate, flash any ESP8266 module with GPIO15 broken-out and connected to 0V via a 1K resistor. I used a master branch build from frightanic.com with modules: bit,file,gpio,net,node,tmr,uart,wifi built on: 2016-12-26 11:44 powered by Lua 5.1.4 on SDK 1.5.4.1(39cb9a32)
With no init.lua present, on power-up, I find that 3.3V is present across the resistor, i.e. 3.3mA so it's not a weak pull-up on a GPIO configured as input.
Many projects I've seen (and some ESP01 modules) have GPIO15 hard-wired to 0V which would cause excessive current to flow out of the device so it would seem to be important to understand what's going on.