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CYD ESP32-3248S035
ESP32 board with 3.5" color screen - ideal for medium-size UIs in embedded or smart home applications.
85.5 × 47.9 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
6· 1 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
10 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | 3V33.3V | power | - | 3.3V output on the CN1 (I2C / temperature-humidity) connector |
| 2 | - | 5VVIN | 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 | 21 | IO21GPIO21 | safe | i2c · pwm | P3 (Extended IO) connector - default I2C SDA; on the 3248S035C capacitive variant this line is the GT911 touch INT (shared) |
| 8 | 22 | IO22GPIO22 | safe | i2c · pwm | P3 (Extended IO) and CN1 (I2C / temperature-humidity) connectors - default I2C SCL |
| 9 | 26 | IO26GPIO26 | safe | dac · pwm | Speaker connector - drives the onboard FM8002A audio amplifier (DAC2), not a raw GPIO at the connector |
| 10 | 35 | IO35GPIO35 | strapping | adc | P3 (Extended IO) connector - input-only (ADC1), no internal pull-up |
Start with these
3 pins with no boot or system involvementIO21GPIO21IO22GPIO22IO26GPIO26
Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| IO0 | GPIO0 | Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| IO35 | GPIO35 | Cannot be used as output; only suitable for input. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| IO1 | U0TXD (GPIO1) | Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console. | USB |
| IO3 | U0RXD (GPIO3) | Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads. | USB |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The CYD ESP32-3248S035 pinout brings out 10 pins - 6 usable GPIO alongside the 3V3 , 5V and GND power rails. Peripheral wiring is straightforward: TX / RX on…
The CYD ESP32-3248S035 pinout brings out 10 pins - 6 usable GPIO alongside the 3V3, 5V 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 pins for sensors and battery monitoring, PWM on 3 pins and 1 true DAC output.
2 of the exposed pins carry boot-time or system duties on the ESP32 (IO0 and IO35) - 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 minutes1
Connect over USB
Install your USB-serial driver (CH340 / CP210x) if no port appears. Not detected? Hold BOOT while plugging in.
2
Match & flash
Set the Tools options shown, then click Upload.
3
Verify it runs
The onboard LED on GPIO21 blinks - swap the pin if your board's LED differs.
Set these in Tools · leave everything else at default
Arduino IDE 2.x — Tools Copy
Board: "ESP32 Dev Module"▸
Flash Size: "4MB (32Mb)"▸
Flash Mode: "DIO"▸
Partition Scheme: "Default 4MB with spiffs (1.2MB APP / 1.5MB SPIFFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option — leave at default
Board: 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
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32 Dev Module
// blink the onboard LED
void setup() {
pinMode(21, OUTPUT);
}
void loop() {
digitalWrite(21, HIGH); delay(500);
digitalWrite(21, LOW); delay(500);
}board to selectesp32dev⧉ copy
[env:cyd-esp32-3248s035]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600Find it: PlatformIO Home ▸ Boards, search
esp32dev — or type it after board =.board to selectesp32dev⧉ copy
esp32:
board: esp32dev
variant: cyd_esp32_3248s035
framework:
type: esp-idf
# blink - GPIO21
output:
- platform: gpio
pin: 21
id: led_out
light:
- platform: binary
name: "LED"
output: led_outFind it: search ESPHome's board list for
esp32dev (same ids as PlatformIO).esptool doesn't pick board settings — a prebuilt .bin already has them baked in. This is just the raw flash command.
esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Build details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32 · 85.5 × 47.9 mmCompute
MCU
ESP32
Clock
240 MHz
SRAM · Flash
520 KB · 4MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
4.2 LE
Antenna
PCB
I/O
GPIO · ADC
6 · 1
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
Micro-USB (UART) · USB-C (UART)
Serial
CH340C
Boot address
0x1000
Display
Screen
TFT · 3.5" · 320x480
Driver
ST7796
Touch
XPT2046
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
1.25 MB · 320 KB
85.5 × 47.9 mm
The CYD ESP32-3248S035 uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with QIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
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 pricesAs an Amazon Associate, ESPboards earns from qualifying purchases.
Resources
Board datasheet google.com↗ ESP32 datasheet espressif.com↗ ESP3D-TFT - Sunton 3.5" ESP32-3248S035R/C hardware reference esp3d.io↗ESP32 CYD ST7796 3.5" board reference (AndroidCrypto) androidcrypto.github.io↗Sunton CYD PlatformIO board definitions (rzeldent) github.com↗ESP32 Cheap Yellow Display community repo github.com↗ardnew ESP32-3248S035 board support package - GPIO pin definitions github.com↗ESP32 Cheap Yellow Display - PINS.md (Sunton connector convention) github.com↗HomeDing ESP32-3248S035 board reference (backlight on IO27, touch pins) homeding.github.io↗
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