RAK3112 documentation

WisBlock
1

Please include the following information, in order for us to help you as effectively as possible.

  • What product do you wish to discuss? RAK3112

  • What firmware are you using? Not relevant

  • What firmware version? Not relevant

  • Computer OS? Not relevant

  • What Computer OS version? Not relevant

  • How often does the problem happen? Not relevant

  • How can we replicate the problem? Read the documentation

  • Provide issue:
    Hello,
    My team is designing a product around RAK3112 module. My engineur came across several documentation issues that makes it impossible to plan with this module, altough it seems to be a very amazing one. Please provide me the informations.
    My engineurs message about the issues:

"Hi, the RAK3112 documentation is not only incomplete, but also quite misleading in several areas.

If you look at the pin table on the module’s official page, many GPIOs are labeled with specific functions. I assume these are meant to represent the default pin assignments, since we all know that ESP32 GPIOs are generally highly configurable thanks to the GPIO matrix. However, the documentation never clarifies this point, which can easily lead to confusion.

In my case, I’m obviously referring to the ESP32-S3 itself, and I plan to choose the GPIOs mainly according to routing convenience and hardware constraints. What really confuses me, though, is the labeling of the analog pins.

According to the RAK documentation, only two analog pins are listed:

GPIO14 / AIN1
GPIO21 / AIN0
It’s not clear why these specific pins are marked as analog. In fact, if you check the official ESP32-S3 documentation, GPIO21 is not connected to the ADC peripheral at all, neither ADC1 nor ADC2. So labeling it as “AIN0” seems incorrect or at least very misleading.

As for GPIO14, it is indeed connected to ADC2_CH3. However, it is well known that using ADC2 on ESP32 devices can cause conflicts when Wi-Fi is enabled. Because of that, for reliable analog readings while using Wi-Fi, it is generally necessary to use ADC1 channels instead, meaning GPIOs in the GPIO0–GPIO10 range, even though RAK’s documentation does not identify them as analog-capable pins."

2

Welcome to RAK forum @Levente ,

There was a documentation error on RAK3112. It was likely an overlap on the documentation of other WisBlock Core.

You can use the GPIO1 and GPIO2 as analog input. This is the analog input we used on our RAK3112 WisBlock Core.

We will update the docs of RAK3112.

3

I can confirm the same issue on my side, and I have now tested it on hardware.

In practice, neither of the two pins documented as analog inputs behaves like a valid analog input in my tests:

  • GPIO21 / AIN0
  • GPIO14 / AIN1

My setup:

  • RAK3112
  • PlatformIO
  • official Espressif Arduino core
  • custom board files from the RAK3112 example/package

Observed results:

  1. analogRead(21) reports that GPIO21 is not an ADC pin in the ESP32-S3 core.
  2. I also tested fixed voltages on the supposed analog inputs, including about 0 V, about 1.5 V, and 3.3 V.
  3. The voltage is physically present on the pins when measured with a multimeter.
  4. However, the ADC readings do not change accordingly on either documented analog input.

So from actual hardware testing, it appears that these GPIOs are not functioning as real analog inputs in practice, despite being documented as:

  • GPIO21 / AIN0
  • GPIO14 / AIN1

This suggests one of the following:

  • the documentation is wrong
  • the board support package / variant is wrong
  • the hardware design does not actually route these signals to usable ADC inputs
  • or there is a hardware design error around the analog routing

Since ESP32-S3 official documentation does not list GPIO21 as an ADC-capable pin, AIN0 on GPIO21 looks especially suspicious.

Can RAK please clarify:

  1. What are the actual valid analog input pins on RAK3112?
  2. Is the GPIO21 / AIN0 documentation incorrect?
  3. Is there a hardware issue or routing limitation on these pins?
  4. Should users avoid both documented analog inputs for ADC use?

At the moment, based on real measurements, neither of the two documented analog inputs gives valid ADC behavior.

4

Welcome to RAK forum Paulo.

We already updated the docs center to avoid confusion.

GPIO1 and GPIO2 are the preferred analog pins.GPIO21 and 14 are incorrect.