CH552G — Enhanced 8-Bit 8051 Microcontroller with Native USB 2.0 Full-Speed

Overview

The CH552G is an ultra-low-cost enhanced 8-bit E8051-core microcontroller manufactured by WCH (Nanjing Qinheng Microelectronics). Available in a compact SOP-16 surface-mount package, it integrates a hardware USB 2.0 Full-Speed device/host controller and transceiver with built-in capacitive touch detection and an on-chip factory USB bootloader.

Costing under $\$ 0.30 $, the CH552G replaces expensive legacy USB microcontrollers (like the ATmega32U4) for simple USB peripheral projects. Because it executes single-cycle instructions (**1T architecture**) at up to **$ 24\text{ MHz}$**, it performs 8x to 15x faster than standard 8051 processors. Featuring open-source toolchain support (SDCC and the ch55xduino Arduino core), the CH552G is widely used in DIY macro-pads, custom mechanical keyboards, USB HID mouse/joystick emulators, USB-to-UART bridges, and hardware security keys.

Quick reference


CPU Core	Enhanced E8051 (1T Single Clock Architecture)
Package	SOP-16 (CH552G) / TSSOP-20 (CH552T) / MSOP-10 (CH552E)
Max Clock Frequency	$24\text{ MHz}$ internal RC oscillator ( $\pm 0.5\%$ accuracy)
Flash Memory	$16\text{ KB}$ ( $14\text{ KB}$ user code + $2\text{ KB}$ pre-flashed USB bootloader)
SRAM	$1280\text{ Bytes}$ ( $256\text{ B}$ internal RAM + $1024\text{ B}$ xRAM)
Data Flash	$128\text{ Bytes}$ non-volatile data storage
Operating Voltage Range	$2.8\text{ V}$ to $5.0\text{ V}$ DC (Built-in $3.3\text{ V}$ LDO for USB transceiver)
USB Peripheral	USB 2.0 Full-Speed (12 Mbps) Device / Host with built-in transceiver
Analog & Touch	6-channel Capacitive Touch-Key + 4-channel 8-bit ADC
Serial Interfaces	2x UART, 1x SPI, 3x Timers, 2x PWM channels

Pinout (SOP-16 Package)

text

                       ┌───┴───┐
     (AIN3/INT0) P3.2 1│ 1   16│ P1.3 (XO / TXD)
     (AIN1/UCC1) P1.4 2│       │15 VCC (Power In)
     (AIN2/MOSI) P1.5 3│       │14 GND
     (RXD1/MISO) P1.6 4│ CH552G│13 P3.7 / UDM (USB D-)
      (SCK/TXD1) P1.7 5│ SOP-16│12 P3.6 / UDP (USB D+)
   (Active-High) RESET 6│       │11 P3.4 (PWM2 / T0)
       (PWM2/TXD) P3.1 7│       │10 V33 (3.3V LDO Output)
                   GND 8│       │9  P3.0 (PWM1 / RXD)
                       └───────┘

Pin	Name	Type	Description
1	`P3.2`	GPIO / Analog	`INT0` / `AIN3` / `TXD1` / `VBUS` detection
2	`P1.4`	GPIO / Analog	`AIN1` / `TIN2` / `T2` / SPI `SCS` / Touch Key 2
3	`P1.5`	GPIO / Analog	`AIN2` / `MOSI` / `PWM1` / Touch Key 3
4	`P1.6`	GPIO / Digital	`MISO` / `RXD1` / `TIN4` / Touch Key 4
5	`P1.7`	GPIO / Digital	`SCK` / `TXD1` / `TIN5` / Touch Key 5
6	`RESET`	Digital Input	External Hardware Reset (Active-HIGH, internal pull-down)
7	`P3.1`	GPIO / Digital	`PWM2` / UART0 `TXD`
8, 14	`GND`	Power	Common Ground ( $0\text{ V}$ )
9	`P3.0`	GPIO / Digital	`PWM1` / UART0 `RXD`
10	`V33`	Power Output/Input	Internal $3.3\text{V}$ LDO output (Connect $0.1\ \mu\text{F}$ bypass cap to GND)
11	`P3.4`	GPIO / Digital	`PWM2` / `RXD1` / Timer0 `T0`
12	`P3.6 / UDP`	USB Data	USB $D+$ Signal (Direct connection to USB Type-C/A D+ pad)
13	`P3.7 / UDM`	USB Data	USB $D-$ Signal (Direct connection to USB Type-C/A D- pad)
15	`VCC`	Power Input	Main $+5\text{V}$ (or $+3.3\text{V}$ ) DC power rail from USB VBUS
16	`P1.3`	GPIO / Digital	Clock Output / `TXD`

Minimal USB Peripheral Hookup

text

         USB Type-C / USB-A Connector
         ┌───────────────────────────┐
         │ VBUS (+5V) ───────────────┼─────────┬──────────────► [Pin 15: VCC]
         │                           │         │                     CH552G
         │                           │   [ 100nF Cap ]               SOP-16
         │                           │         │              [Pin 10: V33] ──[ 100nF Cap ]── GND
         │                           │         │
         │ D- ───────────────────────┼─────────┼──────────────► [Pin 13: UDM / P3.7]
         │ D+ ───────────────────────┼─────────┼──────────────► [Pin 12: UDP / P3.6]
         │                           │         │
         │ GND ──────────────────────┼─────────┴──────────────► [Pin 8, 14: GND]
         └───────────────────────────┘

Flashing & Bootloader Mode

The CH552 comes with a factory-programmed USB ISP bootloader in hardware ROM:

Entering Bootloader: Hold P3.6 / UDP (Pin 12) pulled to $+3.3\text{V}$ (V33) while inserting the USB cable (or during power-on/reset).
Flashing Software: Open-source command-line flashers such as vnproch55x, wchisp, or the Arduino IDE with the ch55xduino board package can flash user code directly over USB in $< 2\text{ seconds}$ .

Common mistakes

Adding series resistors to USB D+ / D- lines: Unlike STM32 or AVR microcontrollers that require $22\ \Omega$ series damping resistors, the CH552 has internal integrated termination matching resistors. Adding external series resistors will cause USB enumeration errors. Connect UDP and UDM directly to the USB connector.
Forgetting the capacitor on Pin 10 (V33): Pin 10 is the internal 3.3V power regulator for the USB physical PHY. If $VCC = 5\text{V}$ , Pin 10 must have a $100\text{ nF}$ ceramic bypass capacitor connected to GND. If powered from a $3.3\text{V}$ rail, tie Pin 10 directly to Pin 15 (VCC).
Active-HIGH Reset: The RESET pin on the CH552 is Active-HIGH (standard 8051 convention), unlike AVR/ARM/STM32 where reset is Active-LOW (NRST). Leaving it disconnected is fine as it has an internal pull-down.

Notes

Pin Count Variants: CH552E (MSOP-10, ultra-compact), CH552G (SOP-16, standard), CH552T (TSSOP-20, full GPIO breakout).