ESP32 Thing Hookup Guide
Espressif's ESP32 is one of the most unique microcontrollers on the market. Its laundry list of features include:
- Dual-core Tensilica LX6 microprocessor
- Up to 240MHz clock frequency
- 520kB internal SRAM
- Integrated 802.11 BGN WiFi transceiver
- Integrated dual-mode Bluetooth (classic and BLE)
- 2.2 to 3.6V operating range
- 2.5 µA sleep current under hibernation
- 32 GPIO
- 10-electrode capacitive touch support
- Hardware accelerated encryption (AES, SHA2, ECC, RSA-4096)
The ESP32 Thing is designed to surround the ESP32 with everything necessary to run and program the microcontroller, plus a few extra goodies to take advantage of the chip's unique features.
Peripherals and I/O
The ESP32 features your standard fare of hardware peripherals, including:
- 18 analog-to-digital converter (ADC) channels
- 3 SPI interfaces
- 3 UART interfaces
- Two I2C interfaces
- 16 PWM outputs
- 2 digital-to-analog converters (DAC)
- Two I2S interfaces
And, thanks to the chip's pin multiplexing feature, those peripherals can be connected to just about any of the 28 broken out I/O pins. That means you decide which pins are RX, TX, MISO, MOSI, SCLK, SDA, SCL, etc.
There are, however, a few hardware features -- namely the ADC and DAC -- which are assigned static pins. The graphical reference below helps demonstrate where you can find those peripherals (click to embiggen!).
One I2C, two of the UART interfaces, and one of the SPI interfaces can be assigned to any pin your project requires.
Input Only Pins: 34-39
Pins 34, 35, 36, 37, 38 and 39 cannot be configured as outputs, but they can be used as either digital inputs, analog inputs, or for other unique purposes. Also note that they do not have internal pull-up or pull-down resistors, like the other I/O pins.
GPIO pins 36-39 are an integral part of the ultra low noise pre-amplifier for the ADC – they are wired up to 270pF capacitors, which help to configure the sampling time and noise of the pre-amp.
From the ESP32 Thing Schematic: GPIO 36-39 are tied together with caps. Those and pins 34 and 35 are input only!
Powering the ESP32 Thing
The two main power inputs to the ESP32 Thing are USB and a single-cell lithium-polymer (LiPo) battery. If both USB and the LiPo are plugged into the board, the onboard charge controller will charge the LiPo battery at a rate of up to 500mA.
The ESP32's operating voltage range is 2.2 to 3.6V. Under normal operation the ESP32 Thing will power the chip at 3.3V. The I/O pins are not 5V-tolerant! If you interface the board with 5V (or higher) components, you'll need to do some level shifting.
The 3.3V regulator on the ESP32 Thing can reliably supply up to 600mA, which should be more than enough overhead for most projects. The ESP32 can pull as much as 250mA during RF transmissions, but we've generally measured it to consume around 150mA -- even while actively transmitting over WiFi. The output of the regulator is also broken out to the sides of the board -- the pins labeled "3V3." These pins can be used to supply external components.
In addition to USB and battery connectors, the VBAT, and VUSB pins are all broken out to both sides of the board. These pins can be used as an alternative supply input to the Thing. The maximum, allowable voltage input to VUSB is 6V, and VBAT should not be connected to anything other than a LiPo battery. Alternatively, if you have a regulated voltage source between 2.2V and 3.6V, the "3V3" lines can be used to directly supply the ESP32 and its peripherals.