Why use Serial.println() to configure sleep mode?

Involute
Posts: 7
Joined: Mon Oct 14, 2019 3:22 am

Why use Serial.println() to configure sleep mode?

Postby Involute » Mon Oct 14, 2019 3:35 am

I'm developing some code that I want to put into deep sleep. According to what I've read, the configuration instruction should be as follows:

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Serial.println(esp_deep_sleep_enable_ext0_wakeup((gpio_num_t)RTC_IN, 0));   // 1 = active high, 0 = active low.
In my application RTC_IN is the pin through which I feed a signal from an external RTC which I'll use to awaken the ESP32.

My code compiles, though I haven't tried to run it yet. Why is the configuration instruction supposed to be placed inside a Serial.println() statement? Especially since the command to go to sleep is not placed in a Serial.println(), as expected:

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esp_deep_sleep_start();
Why not just use:

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esp_deep_sleep_enable_ext0_wakeup((gpio_num_t)RTC_IN, 0);   // 1 = active high, 0 = active low.
Which also compiles, btw.

Also, which pins can be used to trigger the wake-up? Thanks for any tips?

boarchuz
Posts: 135
Joined: Tue Aug 21, 2018 5:28 am

Re: Why use Serial.println() to configure sleep mode?

Postby boarchuz » Mon Oct 14, 2019 5:51 am

Its just passing the return value to println() for debugging. Same as

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esp_err_t result;
result = esp_deep_sleep_enable_ext0_wakeup((gpio_num_t)RTC_IN, 0)
Serial.println(result);
You can see the return values here:
https://docs.espressif.com/projects/esp ... pio_num_ti
So if you see anything other than "0" (ie. ESP_OK) then something has gone wrong. If you don't want to see this, you can remove the println() as you noted.
It also happens to list all the RTC pins there so you know which you can use.

Involute
Posts: 7
Joined: Mon Oct 14, 2019 3:22 am

Re: Why use Serial.println() to configure sleep mode?

Postby Involute » Mon Oct 14, 2019 5:55 am

Ah, got it. Thanks.

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