GPIO pin 9 mystery

[Martinus]

So it seems that pin GPIO-9 (D11) can not be used on some boards, leading to WDT errors. I've checked this today on my NodeMCU board and all GPIO and even PWM commands on port gpio-9 as well as gpio-10 run without issues.
I got these boards at the time that they were just released and could not even program these properly because the IDE was still using QIO mode. Once changed to DIO mode they started to work...

So it looks like the ESP modules on my NodeMCU board have the flash chip connected using two data lines only and GPIO-9 and GPIO-10 are not connected to the flash chip. So the NodeMCU board can use them as free gpio pins.

But it also seems that some (or a lot?) are using ESP modules that have the flash chip connected with 4 datalines (QIO). Then you are out of luck. Maybe these ESP modules look like the newer ones with extra pins on the bottom side but they are likely not wired in the same way as mine.

How to tell? I guess only by taking the shield off and examine pcb traces on the ESP module...

But am i the only one that can use GPIO-9 without errors? Feedback required here. Maybe we can write a wiki on this subject once we figure out which boards could use GPIO-9.

[Shardan]

Hello Martinus,

i've tested with some of my nodeMCU's and got the WDT error.
Following the antenna layout my nodes use ESP-12E.

Sadly i didn't find a schematic by quick google search. It would be interesting if there is
some additional circut around GPIO9 making it availlable.

Regards
Shardan

[Martinus]

Just to be more sure for myself, created this ruleset and configured push button on the GPIO-0 button on the NodeMCU V1.0:

Code: Select all

on SW1#Switch do
  gpio 9,[SW1#Switch]
  gpio 10,[SW1#Switch]
endon

And keep pushing the button shows this log:
EVENT: SW1#Switch=0.00
ACT : gpio 9,0
SW : GPIO 9 Set to 0
ACT : gpio 10,0
SW : GPIO 10 Set to 0
SW : State 1
EVENT: SW1#Switch=1.00
ACT : gpio 9,1
SW : GPIO 9 Set to 1
ACT : gpio 10,1
SW : GPIO 10 Set to 1
SW : State 0
EVENT: SW1#Switch=0.00
ACT : gpio 9,0
SW : GPIO 9 Set to 0
ACT : gpio 10,0
SW : GPIO 10 Set to 0
SW : State 1
EVENT: SW1#Switch=1.00
ACT : gpio 9,1
SW : GPIO 9 Set to 1
ACT : gpio 10,1
SW : GPIO 10 Set to 1
SW : State 0
EVENT: SW1#Switch=0.00
ACT : gpio 9,0
SW : GPIO 9 Set to 0
ACT : gpio 10,0
SW : GPIO 10 Set to 0
SW : State 1
EVENT: SW1#Switch=1.00
ACT : gpio 9,1
SW : GPIO 9 Set to 1
ACT : gpio 10,1
SW : GPIO 10 Set to 1

No WDT.