What is touch_pad_get_status() supposed to return?

Question

What I want to do: I have 7 touch buttons on my board (ESP32 TTGO T-Display) and I want to attach interrupts to everyone, calling the same function. In this function I would like to use touch_pad_get_status() or other to get which button was touched. Then a switch case would do the rest.

What I'm facing: This code

  Serial.print("Button ");
  uint32_t touch = touch_pad_get_status();
  Serial.println(String(touch));

always returns 0, no matter what.

What I've tried: Including this part of code to the setup

  touch_pad_init();
  touch_pad_set_fsm_mode(TOUCH_FSM_MODE_TIMER); //tried the SW MODE too
  touch_pad_io_init(TOUCH_PAD_GPIO15_CHANNEL);

But nothing seem to work. I don't want to make 7 different functions...

Thanks in advance.

Answer 1

As pointed out from people in the comments, things need to be different. If you use the function touchAttachInterrupt, things are a bit simpler. The example that comes with the ESP32 library is enough to make you understand.

If you want to do what I did, this is how:

  touch_pad_init();
  touch_pad_set_fsm_mode(TOUCH_FSM_MODE_TIMER);
  touch_pad_config(TOUCH_PAD_GPIO2_CHANNEL, 500);
  touch_pad_config(TOUCH_PAD_GPIO15_CHANNEL, 500);
  touch_pad_config(TOUCH_PAD_GPIO13_CHANNEL, 500);
  touch_pad_isr_register(TouchButton, NULL);
  touch_pad_intr_enable();

Put this code in the setup(). Of course needs the init(), but also needs to be set to timer mode, or otherwise you're going to need to start() probably. The config() is to configure the pin as an interrupt. I've set 500 in the threshold because the readings of touch_pad_read() told me it went from 800 untouched to 50 touched, so the midterm I chose 500. isr_register is the function that tells to call TouchButton(), with NULL as argument to it.

void TouchButton(void *arg)
{
  uint32_t touch = touch_pad_get_status();
  touch_pad_clear_status();
  Serial.print("Button ");
  Serial.println(String(touch));
}

This is the declaration of the callback function I've done. It should be noted that clear_status() should be called as soon as possible after the get_status(), preventing the system from panicking (that's the name). You'll also see in the serial monitor that each button represents a power of 2. That's because the get_status() returns the pin mask in binary. So just do something similar to this

for (int i = 0; i < TOUCH_PAD_MAX; i++) {
    if ((pad_intr >> i) & 0x01) {
        s_pad_activated[i] = true;
    }
}

and you'll get a vector of which one was pressed.