Neopixel initialization affects SDA and SCL pin direction on QT Py ESP32-S2

[bjfischb]

I have had an application running on a QT Py ESP32-S2 for about 4 months. The application uses most of the GPIO as digital inputs/outputs, and also uses the built-in neopixel as a status indicator.

I updated libraries and the ESP32 board package regularly based on notifications in the Arduino IDE that a library can be updated. After updating libraries, I re-compile and upload the code to all my projects. I don't keep strict track of all the changes, so I can't pinpoint exactly when this problem ocurred.

I noticed a few weeks ago that my application had failed, and my debug pointed to a strange behavior on the QT Py ESP32-S2: the code location of the pin direction declarations (for pins used as digital I/O) relative to the neopixel initialization causes the direction settings to either be correct or incorrect. I narrowed down the code to create illustrative examples:

This code results in GPIO6 and GPIO7 correctly being configured as inputs with pullup resistors

#include <Adafruit_NeoPixel.h> 

//GPIO39 is PIN_NEOPIXEL on QTPY
Adafruit_NeoPixel neoLED = Adafruit_NeoPixel(1, 39, NEO_GRB + NEO_KHZ800);

void setup() {


//GPIO38 is NEOPIXEL_POWER on QTPY
  pinMode(38, OUTPUT);
  digitalWrite(38, HIGH);  

  neoLED.begin();  
  neoLED.setPixelColor(0, 20, 8, 20);
  neoLED.show();

  pinMode(7, INPUT_PULLUP);
  pinMode(6, INPUT_PULLUP);  
}

void loop() {
}

But this code results in GPIO6 and GPIO7 incorrectly being configured as outputs pulled to ground

#include <Adafruit_NeoPixel.h> 

//GPIO39 is PIN_NEOPIXEL on QTPY
Adafruit_NeoPixel neoLED = Adafruit_NeoPixel(1, 39, NEO_GRB + NEO_KHZ800);

void setup() {

  pinMode(7, INPUT_PULLUP);
  pinMode(6, INPUT_PULLUP);  

//GPIO38 is NEOPIXEL_POWER on QTPY
  pinMode(38, OUTPUT);
  digitalWrite(38, HIGH);  

  neoLED.begin();  
  neoLED.setPixelColor(0, 20, 8, 20);
  neoLED.show();
}

void loop() {
}

Some additional information:

1. For the working case with pinMode statements after neopixel initialization, I confirmed that the I/O are inputs with pullup by measuring short circuit current to ground and seeing that the effective resistance to Vdd was 45k-ohm, consistent with the ESP32-S2 datasheet
2. For the non-working case with pinMode statements before the neopixel initialization, I confirmed that the I/O are outputs driven to ground by (very) briefly measuring short circuit current to Vdd and seeing about 30mA, consistent with the ESP32-S2 datasheet
3. The problem seems to happen only with GPIO6 and GPIO7 (SDA and SCL on the QT Py ESP32-S2 board). All the other GPIO I am using in my application are initialized correctly, even if the pinMode statements are before the neopixel initialization
4. I ran the same code on a Feather ESP32-S2 TFT and I did not see a problem with SDA or SCL when the pinMode statements were before the neopixel initialization (the Feather uses different GPIO for neopixel power and data, so I changed the code for that). So, this seems specific to the Qt Py ESP32-S2
5. Like I said above, I noticed the application failure in the past month or so. Before that, the application was working correctly with the pinMode statements before the neopixel initialization. So, I'm thinking a recent update may be responsible.
6. Here are the versions I am running:

• ESP32 board package: 3.1.3
• Adafruit NeoPixel 1.12.5

Any help on this would be appreciated!