Adafruit QT Py ESP32-S3
The Adafruit QT Py ESP32-S3 brings the ESP32-S3 into Adafruit's compact QT Py form factor with STEMMA QT (Qwiic) connectivity. At 22x17.8mm, it is designed for quick sensor integration using Adafruit's plug-and-play I2C ecosystem, with full CircuitPython and Arduino support out of the box.
Best for Adafruit STEMMA QT ecosystem projects, skip if you need PSRAM or many GPIO pins.
Where to Buy
Pros
- Built-in STEMMA QT / Qwiic connector for plug-and-play I2C sensors
- Excellent CircuitPython and Arduino support from Adafruit
- USB-C with OTG support for native USB functionality
- Adafruit's extensive tutorial and learning resources
Cons
- No PSRAM on the standard variant — limits AI/ML and camera applications
- Only 13 GPIO pins exposed — constraining for complex projects
- No battery charging circuit unlike the XIAO or Thing Plus
STEMMA QT Ecosystem
The defining feature of the QT Py is the STEMMA QT connector — a JST SH 4-pin connector compatible with SparkFun's Qwiic standard. This connector carries I2C data (SDA, SCL) plus 3.3V power and ground. You can daisy-chain multiple I2C devices without any soldering or breadboarding.
Adafruit sells over 200 STEMMA QT-compatible sensor breakouts covering temperature, humidity, pressure, light, gas, accelerometers, gyroscopes, magnetometers, GPS, and more. Each comes with a CircuitPython library. For educators and rapid prototypers, this plug-and-play ecosystem eliminates wiring errors and reduces setup time from hours to minutes.
CircuitPython First
While all ESP32-S3 boards support Arduino and ESP-IDF, the QT Py is optimized for CircuitPython. Adafruit preloads CircuitPython firmware, and the board appears as a USB drive when connected. You write Python code in any text editor, save it to the drive, and it runs immediately — no compilation, no flashing, no IDE required.
The 8MB flash provides ample space for CircuitPython, libraries, and application code. CircuitPython's trade-off is performance — it is interpreted Python running on a microcontroller, so compute-intensive tasks will be slower than compiled C/C++ via Arduino or ESP-IDF. For sensor reading and data logging, the performance is more than adequate.
Hardware Trade-offs
The standard QT Py ESP32-S3 ships without PSRAM, which is a significant limitation compared to the XIAO ESP32S3 or the DevKitC that include 8MB. Without PSRAM, camera frame buffers and ML model weights cannot be loaded. An N8R2 variant with 2MB PSRAM exists but is less commonly stocked.
The 13 GPIO pins and single STEMMA QT connector are sufficient for typical sensor projects but limit hardware complexity. There is no battery charging circuit — you need an external charger or a different board for portable applications.
Full Specifications
Processor
| Specification | Value |
|---|---|
| Architecture | Xtensa LX7 |
| CPU Cores | 2 |
| Clock Speed | 240 MHz |
Memory
| Specification | Value |
|---|---|
| Flash | 8 MB |
| SRAM | 512 KB |
Connectivity
| Specification | Value |
|---|---|
| WiFi | 802.11 b/g/n |
| Bluetooth | 5.0 |
I/O & Interfaces
| Specification | Value |
|---|---|
| GPIO Pins | 13 |
| ADC Channels | 10 |
| SPI | 1 |
| I2C | 1 |
| UART | 1 |
| USB | USB-C (OTG) |
| STEMMA QT / Qwiic | 1x STEMMA QT / Qwiic |
Power
| Specification | Value |
|---|---|
| Input Voltage | 5 V |
| Deep Sleep Current | ~15 uA |
Physical
| Specification | Value |
|---|---|
| Dimensions | 22 x 17.8 mm |
| Form Factor | QT Py (Adafruit compact) |
Who Should Buy This
The STEMMA QT connector lets you daisy-chain Adafruit's 200+ I2C sensor breakouts without soldering. CircuitPython firmware is preloaded. Plug in, write Python, read sensors.
CircuitPython turns the board into a USB drive where you edit code in a text editor. No IDE, compiler, or toolchain setup needed. Adafruit's tutorials and guides are beginner-friendly.
No PSRAM on the standard QT Py variant means no room for camera frame buffers or ML models. The ESP32-S3-DevKitC has 8MB PSRAM for these applications.
Better alternative: ESP32-S3-DevKitC-1
No battery charging circuit. The XIAO ESP32S3 offers a similar form factor with built-in LiPo charging, and the Thing Plus ESP32-S3 adds a fuel gauge.
Better alternative: Seeed Studio XIAO ESP32S3
Frequently Asked Questions
What is STEMMA QT / Qwiic?
STEMMA QT (Adafruit) and Qwiic (SparkFun) are the same JST SH 4-pin I2C connector standard. Boards and sensors from both companies are cross-compatible. You connect them with small cables — no soldering needed.
Does the QT Py ESP32-S3 have PSRAM?
The standard variant does not include PSRAM. An N8R2 variant with 2MB PSRAM exists but is less common. For 8MB PSRAM, consider the XIAO ESP32S3 or the ESP32-S3-DevKitC.
Can I use Arduino with the QT Py ESP32-S3?
Yes. While Adafruit emphasizes CircuitPython, the QT Py fully supports Arduino IDE and PlatformIO via the ESP32 Arduino Core. You can switch between CircuitPython and Arduino by flashing different firmware.
QT Py vs XIAO ESP32S3: which is better?
The QT Py wins on ecosystem (STEMMA QT connector, CircuitPython focus, Adafruit tutorials). The XIAO wins on specs (8MB PSRAM, battery charging, camera option with Sense variant). Both are similar size at around 21-22mm.
How many I2C sensors can I connect to the QT Py?
Up to 127 devices on the single I2C bus, though practically 10-20 is common. STEMMA QT cables daisy-chain, so each sensor board passes the bus to the next. Address conflicts are the main limitation — most sensors have configurable I2C addresses.