38-pin development boards are especially well suited to experiment with all ESP32S features as they provide access to almost every microcontroller pin.
At the same time, it makes such boards exceptionally large and a primary target for using expansion boards instead of classic breadboards.
ESP32S 38P/V4/Goouu Expansion Board
This expansion board is suited for most 38pin ESP32S boards with a width of 24mm or 25.5mm (which is why there are three pin rows):
This expansion board was originally designed for the ESP32 DevKitC V4 which has a width of 25.5mm and plugs into the two outer pin rows, with the antenna facing outwards.
Caveats
There are two caveats to watch out for when using this board:
Firmware Upload
You cannot use the USB connectors on this board to upload firmware to the microcontroller. The USB connectors on the expansion port are solely used to supply power.
When you want to upload new firmware to the microcontroller via USB, you need to use the original USB connector on the development board, and not the USB connectors on the expansion board.
The recommended way generally is to enable OTA (over-the-air) updates on your microcontroller so you can upload new firmware wirelessly. The easiest way to enable OTA is to use ESPHome.
Pin Offset
The pins on the expansion board do not exactly align with the pins on the development board. This can easily lead to wrongly connected wires when you connect wires based on the development board labels.
Here is an example:
The pin GPIO4 on the development board surfaces slightly offset to the right as P4 on the expansion board, and when you connect wires, you could easily connect the wire wrongly to P0 (GPIO0) when in reality you want to connect to GPIO4.
When using expansion boards, make it a habit to always conform to the labels printed on the expansion board only.
Aside from the offset, another benefit of expansion boards is their better PCB quality: labels are much more readably marked compared to many development boards.
Dedicated Power Supply Pins
What sets this board apart from most others are the dedicated red and black power supply pins per GPIO:
Each GPIO is exposed via a yellow male pin that is accompanied by a red and a black power supply pin. Being able to route power to any component right at the pin level reduces wires and clutter.
Selecting Component Voltage
Components require either 3.3V or 5V - which is why you can choose the voltage supplied by the red pins. A jumper controls this voltage:
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3.3V: When the jumper is set to the 3.3V position, then the 3.3V output from the plugged in development board is routed to the red pins.
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5V: When the jumper is set to the 5V position, then the extension boards’ 5V is available at all red pins.
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Custom: When no jumper is used, then all red pins are disconnected. More precisely, they are connected to the middle pin of the jumper terminal. To route custom signals to the red pins, connect the desired signal to this middle pin.
Since the expansion board is not producing 3.3V, the maximum current for 3.3V depends entirely on the built-in voltage regulator on the development board you plugged in.
Additional Pins
VCC (3.3V), GND, RX, and TX are exposed via a separate pin pad.
Power Supply
The board comes with a solid 800mA 5V LD1117C50 voltage regulator that can be powered by a USB-C or Micro-USB connector, or a round DC plug. It accepts input voltage up to 15V.
Microcontroller Supply
The board supplies 5V to the microcontroller, and in turn draws power from its 3.3V output pin.
Two dedicated 5V auxiliary pins are powered directly off the voltage regulator, and two dedicated 3.3V auxiliary pins are powered by the microcontroller board.
As mentioned, the jumper controls the voltage routed to the red pins.
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(content created Jul 03, 2024 - last updated Jul 05, 2024)