CYD ESP32-3248S035
ESP32 board with 3.5" color screen - ideal for medium-size UIs in embedded or smart home applications.
CYD ESP32-3248S035 Pinout
27 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | 3V33.3V | power | - | 3.3V output on the CN1 temperature/humidity connector (pin 1) |
| 2 | - | VIN5V | power | - | 5V input on the P1 power/serial connector (4P 1.25 power-supply base) |
| 3 | - | GND | ground | - | Ground - present on the P1, P3, CN1 and speaker connectors |
| 4 | 0 | IO0BOOTGPIO0 | control | - | BOOT button (GPIO0 strapping pin) - usable as an input |
| 5 | 1 | IO1TXGPIO1 | uart | uart | P1 serial connector - U0TXD, shared with the CH340 USB programming/serial |
| 6 | 3 | IO3RXGPIO3 | uart | uart | P1 serial connector - U0RXD, shared with the CH340 USB programming/serial |
| 7 | - | NC | - | CN1 pin 3 - not connected (read off macsbug's photo of the board) | |
| 8 | 21 | IO21GPIO21 | safe | i2c · pwm | P3 (Extended IO) connector, and the single data line of CN1 (a DHT-style temperature/humidity socket, not an I2C pair); on the 3248S035C capacitive variant this line is also the GT911 touch INT |
| 9 | 22 | IO22GPIO22 | safe | i2c · pwm | P3 (Extended IO) connector only - default I2C SCL. Not on CN1, whose one data line is IO21 |
| 10 | 26 | IO26GPIO26 | safe | dac · pwm | Speaker connector - drives the onboard FM8002A audio amplifier (DAC2), not a raw GPIO at the connector |
| 11 | 35 | IO35GPIO35 | strapping | adc | P3 (Extended IO) connector - input-only (ADC1), no internal pull-up |
| 12 | 14 | strapping | - | TFT SCK (HSPI) on the ST7796 display; the resistive touch controller shares this clock | |
| 13 | 13 | strapping | - | TFT MOSI (HSPI); shared with the XPT2046 touch controller on the R board | |
| 14 | 12 | strapping | - | TFT MISO (HSPI); shared with the XPT2046 touch controller, and a strapping pin | |
| 15 | 15 | strapping | - | TFT chip select; also a strapping pin | |
| 16 | 2 | strapping | - | TFT data/command (RS) | |
| 17 | 27 | safe | - | TFT backlight - PWM it to dim the panel. Note this is IO27, where the 2432S028 uses IO21 | |
| 18 | 33 | safe | - | Touch chip select. On the 3248S035C this pin is the GT911 I2C SDA instead | |
| 19 | 36 | strapping | - | Touch interrupt (IRQ); input-only | |
| 20 | 18 | safe | - | microSD clock (VSPI); free only when the card slot is unused | |
| 21 | 23 | safe | - | microSD MOSI (VSPI); free only when the card slot is unused | |
| 22 | 19 | safe | - | microSD MISO (VSPI); free only when the card slot is unused | |
| 23 | 5 | strapping | - | microSD chip select (VSPI); free only when the card slot is unused, and a strapping pin | |
| 24 | 4 | safe | - | Red leg of the onboard RGB LED | |
| 25 | 16 | safe | - | Green leg of the onboard RGB LED | |
| 26 | 17 | safe | - | Blue leg of the onboard RGB LED | |
| 27 | 34 | strapping | - | LDR (CDS photo-resistor); input-only (ADC1) |
Start with these
3 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
13 pins · 8 things to knowIO0 Bootstrapping pin (enter bootloader when low); internal pull-up. Strapping
Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.
IO1 Default UART0 TX pin for USB-serial programming and console. UART
Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.
IO3 Default UART0 RX pin for USB-serial programming (console input). UART
Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.
IO35 Input-only GPIO (no output driver); ADC1 channel 7. Other
Cannot be used as output; only suitable for input.
GPIO27 TFT backlight - PWM it to dim the panel. Note this is IO27, where the 2432S028 uses IO21 onboard hardware
Wired to the display backlight on this board. The pin is yours if you give that up, but nothing else can share it.
GPIO18GPIO23GPIO19GPIO5 Used by the microSD card slot onboard hardware
Wired to the microSD card slot on this board. The pin is yours if you give that up, but nothing else can share it.
- microSD clock (VSPI); free only when the card slot is unused
- microSD MOSI (VSPI); free only when the card slot is unused
- microSD MISO (VSPI); free only when the card slot is unused
- microSD chip select (VSPI); free only when the card slot is unused, and a strapping pin
GPIO4GPIO16GPIO17 Used by the onboard RGB LED onboard hardware
Wired to the onboard RGB LED on this board. The pin is yours if you give that up, but nothing else can share it.
- Red leg of the onboard RGB LED
- Green leg of the onboard RGB LED
- Blue leg of the onboard RGB LED
GPIO34 LDR (CDS photo-resistor); input-only (ADC1) onboard hardware
Wired to the LDR light sensor on this board. The pin is yours if you give that up, but nothing else can share it.
Only if you know the tricks
7 pins · 2 things to knowGPIO14GPIO13GPIO12GPIO15GPIO2 Used by Display (ST7796) onboard hardware
Wired to Display (ST7796) on this board, which is soldered down. Driving it from your own code breaks that function.
- TFT SCK (HSPI) on the ST7796 display; the resistive touch controller shares this clock
- TFT MOSI (HSPI); shared with the XPT2046 touch controller on the R board
- TFT MISO (HSPI); shared with the XPT2046 touch controller, and a strapping pin
- TFT chip select; also a strapping pin
- TFT data/command (RS)
GPIO33GPIO36 Used by the touch controller (XPT2046) onboard hardware
Wired to the touch controller (XPT2046) on this board, which is soldered down. Driving it from your own code breaks that function.
- Touch chip select. On the 3248S035C this pin is the GT911 I2C SDA instead
- Touch interrupt (IRQ); input-only
The CYD ESP32-3248S035 pinout brings out 27 pins - 22 usable GPIO alongside the 3V3, VIN and GND power rails.
Peripheral wiring is straightforward: TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.
Beyond plain digital I/O you get 1 ADC-capable pin for sensors and battery monitoring, PWM on 3 pins and 1 true DAC output.
13 of the exposed pins carry boot-time or system duties on the ESP32 (IO0, IO1, IO3 and 10 more) - check the guidance above before wiring anything to them. IO21, IO22 and IO26 are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 4MB (32Mb) Flash Mode: DIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO21 - wire an LED and resistor to it
void setup() {
pinMode(21, OUTPUT);
}
void loop() {
digitalWrite(21, HIGH); delay(500);
digitalWrite(21, LOW); delay(500);
}[env:cyd-esp32-3248s035]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32dev - or type it after board =.esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO21
output:
- platform: gpio
pin: 21
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32dev (same ids as PlatformIO).esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Downloads
Free for non-commercial use, credit espboards.dev · License
Board illustration
The bare CYD ESP32-3248S035 board drawn to scale at 101.5 × 54.9 mm, with no pin labels on it. Made for slide decks, wiring diagrams and project write-ups where a photo is too busy. Take the scalable SVG for print or editing, the high-resolution PNG to drop straight in, or the transparent PNG when you need it with no background behind it.
Pinout diagram
Every pin on both sides of the board with its functions, drawn by ESPboards from the ESP32 Series Datasheet v5.3 - the same sheet shown at the top of this page. The PNG is a high-resolution image for screens, the SVG is vector so it stays sharp at any size, and the PDF is laid out to print on A4 or Letter.
Yours to use, share and adapt for non-commercial work, as long as you credit espboards.dev - the full terms and ready-made credit lines are here.
Specifications
ESP32 · 101.5 × 54.9 mm · vs other ESP32 chips →Dimensions
About this board
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE. Sibling CYD boards cover the ESP32-S3 and ESP32-C3, so you can change radios or horsepower without changing the footprint.
The $22.00 price tag is typical for a CYD board.
Around the module: a TFT 3.5" 320x480 display with touch, a microSD slot, a speaker connector, an ambient-light sensor and Reset/Boot buttons.
- Sold in resistive (XPT2046) and capacitive (GT911) touch variants
- Discrete RGB LED driven by GPIO 4 (R), 16 (G), 17 (B)
- Onboard audio amplifier (FM8002A) driving the speaker connector
- GPIO broken out on 3 JST 1.25 connectors instead of breadboard headers
Where to buy
prices are typical street pricesResources
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