digitalRead only works with INPUT mode

[microbuilder]

digitalRead (wiring_digital.c) only works when the pin is configured as an input, but should also work checking the state of an output pin.

Code

The following code will always return '0' (low) even though the GPIO pin is clearly being toggled:

#include <Arduino.h>

const int baudrate = 115200;

void setup() {
  Serial.begin (baudrate);
  
  pinMode(PIN_LED2, OUTPUT);
}

void loop() {
  int val = 0;

  digitalWrite(PIN_LED2, HIGH);
  val = digitalRead(PIN_LED2);
  Serial.println(val, HEX);
  delay(500);

  digitalWrite(PIN_LED2, LOW);
  val = digitalRead(PIN_LED2);
  Serial.println(val, HEX);
  delay(500);
}

Issue

The nRF5x has separate NRF_GPIO->IN and NRF_GPIO->OUT registers. The current implementation of digitalRead assumes the pins is always configured as an input when we read it, but while this is true 95% of the time we should detect the pin mode and if it is an OUTPUT use the OUT register:

int digitalRead( uint32_t ulPin )
{
  if (ulPin >= PINS_COUNT) {
    return 0;
  }

  ulPin = g_ADigitalPinMap[ulPin];

  return ((NRF_GPIO->IN >> ulPin) & 1UL) ? HIGH : LOW ;
}

[hathach]

I encounter this bug as well when trying to add digitalToggle(). Will fix and also open issue on sandeep repo as well.