PA7 digitalRead always returns 0 after Serial.begin() + Serial.end()

[vladkozlov69]

PA7 digitalRead always returns 0 after Serial.begin() + Serial.end()

Here is the code to reproduce the issue:

void setup()
{
	Serial.begin(115200);
}


void loop()
{
	Serial.println(millis());
	Serial.end();
	pinMode(PA7, INPUT_PULLUP);
	int status = digitalRead(PA7);
	Serial.begin(115200);
	Serial.println(status);
	delay(200);
}

I guess Serial.end() should release the resources and bindings so PA7 should be available to read?

[vladkozlov69]

I found that *void serial_free(serial_t obj) does not perform a correct cleanup.

So after Serial.end() I just added

Pinmux_Config((PinName)g_APinDescription[LOG_TX].pinname, PINMUX_FUNCTION_GPIO);

Here is the demo code:

#define RESET_PIN PA7

void setup()
{
	Serial.begin(115200);
	pinMode(LED_G, OUTPUT);
	pinMode(LED_R, OUTPUT);
	digitalWrite(LED_G, LOW);
	digitalWrite(LED_R, LOW);
}


unsigned long resetTimerStart;
unsigned long resetTimerEnd;

void loop()
{
	Serial.println(millis());
	Serial.end();
	Pinmux_Config((PinName)g_APinDescription[LOG_TX].pinname, PINMUX_FUNCTION_GPIO);
	pinMode(RESET_PIN, INPUT);
	if (digitalRead(RESET_PIN) == LOW)
	{
		digitalWrite(LED_G, HIGH);
		resetTimerStart = millis();
		while(digitalRead(RESET_PIN) == LOW);
		resetTimerEnd = millis();
	}
	digitalWrite(LED_G, LOW);
	if (resetTimerEnd - resetTimerStart >= 5000)
	{
		digitalWrite(LED_R, HIGH);
	}

	Serial.begin(115200);
	Serial.print("Factory settings button was pressed for ");
	Serial.print(resetTimerEnd - resetTimerStart);
	Serial.println(" milliseconds.");
	delay(200);
}