gpio_config_t.pin_bit_mask inconsistent behavior?

[00coday]

Running a NodeMCU ESP32S, Arduino IDE 1.8.5, and ESP32 library 1.0.4.

I am trying to run gpio_config for multiple input pins with the ultimate goal of adding interrupts - the project is a race track timer using photodiodes as inputs for the lane ends. Right now I'm using GPIOs 8 and 15. I get inconsistent requirements with the gpio_config_t.pin_bit_mask - for pin 15, the mask looks like:

`io_conf.pin_bit_mask = 0B00000000000000001000000000000000;`

The "1" is in the 16th position from the right and makes sense if the first pin is pin 0 - everything works fine.

Based on this I surmise that the pin to be affected is based on bit position in the bit mask. makes sense. From there I would think that the bit mask for pin 8 would look like:

`io_conf.pin_bit_mask = 0B00000000000000000000000100000000`

the "1" is in the 9th position - pin 8 if the starting pin is 0. But that throws:

[Codebox]ets Jun 8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Guru Meditation Error: Core 1 panic'ed (Interrupt wdt timeout on CPU1)
Core 1 register dump:
PC : 0x4000c271 PS : 0x00060034 A0 : 0x80088c0f A1 : 0x3ffb1e40
A2 : 0x3ffb0058 A3 : 0x3f4046dc A4 : 0x00000014 A5 : 0x3ffbe790
A6 : 0x3ffbe7d8 A7 : 0x00000001 A8 : 0x00000001 A9 : 0x3f4046dd
A10 : 0x000000a5 A11 : 0x00000000 A12 : 0x800897f7 A13 : 0x3ffbe760
A14 : 0x00000008 A15 : 0x00000001 SAR : 0x0000001f EXCCAUSE: 0x00000006
EXCVADDR: 0x00000000 LBEG : 0x00000000 LEND : 0x00000000 LCOUNT : 0x00000000

Backtrace: 0x4000c271:0x3ffb1e40 0x40088c0c:0x3ffb1e60 0x4008a620:0x3ffb1e80 0x4008a5d6:0x3ffb1ea0 0x400d1d6b:0x3ffb1f78

Core 0 register dump:
PC : 0x400e9dc2 PS : 0x00060334 A0 : 0x800d3e16 A1 : 0x3ffbbff0
A2 : 0x00000000 A3 : 0x00000001 A4 : 0x00000000 A5 : 0x00000001
A6 : 0x00060320 A7 : 0x00000000 A8 : 0x800d39de A9 : 0x3ffbbfc0
A10 : 0x00000000 A11 : 0x40084e58 A12 : 0x00060320 A13 : 0x3ffbb970
A14 : 0x00000000 A15 : 0x3ffbbce0 SAR : 0x00000000 EXCCAUSE: 0x00000006
EXCVADDR: 0x00000000 LBEG : 0x00000000 LEND : 0x00000000 LCOUNT : 0x00000000

Backtrace: 0x400e9dc2:0x3ffbbff0 0x400d3e13:0x3ffbc010 0x400897e6:0x3ffbc030 0x400882f5:0x3ffbc050
[/Codebox]

I did some googling and found that for pin 8 the mask needed to be 0x8 or:

`io_conf.pin_bit_mask = 0B00000000000000000000000000001000;`

This works but is the binary representation of the number 8, not a bit map representing pin 8 when starting from 0.

All of the examples I have seen use some sort of bit shifting based on the input pin # - that is backed up by the bit map for 15, but not 8... Is this an inconsistent behavior in how different pins are represented in the bit mask, or am I missing a fundamental ESP32 development concept here?

Test code looks like:


[Codebox]#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "driver/gpio.h"

void IRAM_ATTR isr_lane(void* arg){
uint32_t gpio_num = (uint32_t) arg;
Serial.println( gpio_num );
}

void setup() {
// put your setup code here, to run once:
Serial.begin(115200);

uint8_t pin = 8;
gpio_config_t io_conf;
io_conf.intr_type = (gpio_int_type_t)GPIO_PIN_INTR_DISABLE;
io_conf.pull_down_en = GPIO_PULLDOWN_DISABLE;
io_conf.pull_up_en = GPIO_PULLUP_DISABLE;
//io_conf.pin_bit_mask = 0B00000000000000001000000000000000; //works for pin 15
//io_conf.pin_bit_mask = 0B00000000000000000000000000001000; //works for pin 8
io_conf.pin_bit_mask = 0B00000000000000000000000100000000; //should work for pin 8
io_conf.mode = GPIO_MODE_INPUT;
gpio_config(&io_conf);
gpio_set_intr_type((gpio_num_t)pin, GPIO_INTR_HIGH_LEVEL);
gpio_install_isr_service(0);
gpio_isr_handler_add((gpio_num_t)pin, isr_lane, (void*) pin);
}

void loop() {
// put your main code here, to run repeatedly:

}[/Codebox]

[ESP_Sprite]

GPIO8 normally can't be used as it is connected to the internal flash chip.