CP2102 USB-UART board: specs and pinout
A USB-to-serial adapter board built around the CP2102 bridge, used to program and talk to microcontrollers over a virtual COM port. Spec rows below are for the original CP2102 (Rev 1.0, 10/04); the stocked board may carry a CP2102N, which differs. This page covers the CP2102 chip; the board (micro-USB socket, header labels, voltage output) is not covered by an official document.
Specs
| Spec | Value | Source |
|---|---|---|
| USB interface (original CP2102 Rev 1.0) | USB 2.0 full-speed (12 Mbps); integrated transceiver, no external resistors, no crystal | source Features (p.1) |
| UART baud rate (original CP2102 Rev 1.0) | 300 bps to 1 Mbit/s; data bits 5, 6, 7, 8; stop bits 1, 1.5, 2 | source Features (p.1) |
| UART signals (original CP2102 Rev 1.0) | TXD, RXD, RTS, CTS, DTR, DSR, DCD, RI | source Features (p.1); Table 4 (p.6) |
| Supply, self-powered (VDD) (original CP2102 Rev 1.0) | 3.0 V to 3.6 V | source Table 2 Global DC Electrical Characteristics (p.5) |
| Supply, USB bus-powered (REGIN) (original CP2102 Rev 1.0) | 4.0 V to 5.25 V into the on-chip regulator | source Table 8 Voltage Regulator Electrical Specifications (p.13) |
| On-chip regulator output (original CP2102 Rev 1.0) | 3.3 V (3.0-3.6 V) at 1 to 100 mA; maximum regulator supply current 100 mA | source Table 8 (p.13) |
| Supply current (original CP2102 Rev 1.0) | 26 mA typ at VDD 3.3 V; 330 uA typ in USB suspend | source Table 2 (p.5) |
| UART output levels (original CP2102 Rev 1.0) | VOH min VDD - 0.7 V at -3 mA; VOL max 0.6 V at 8.5 mA | source Table 3 UART and Suspend I/O DC Electrical Characteristics (p.5) |
| UART input levels (original CP2102 Rev 1.0) | VIH 2.0 V min; VIL 0.8 V max; absolute maximum on any I/O pin 5.8 V | source Table 3 and Table 1 (p.5) |
| Operating temperature (original CP2102 Rev 1.0) | -40 C to +85 C | source Table 2 (p.5) |
Power
| Value | Source | |
|---|---|---|
| Supply | Original CP2102 Rev 1.0: Bus-powered from USB through the on-chip regulator (REGIN 4.0-5.25 V), or VDD 3.0-3.6 V when self-powered | source Table 2 (p.5); Table 8 (p.13) |
| Current | Original CP2102 Rev 1.0: 26 mA typ at VDD 3.3 V | source Table 2 (p.5); Table 8 (p.13) |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
Rows are the CP2102 chip's pins (MLP-28). The micro-USB board's header labels and order, whether it brings out 3V3 and 5V pins, and whether it uses a CP2102 or the newer CP2102N are not covered by an official document, so check the printed labels on your board.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| TXD | Asynchronous data output (UART transmit) | VOH min VDD - 0.7 V at -3 mA | Goes to the target's RX; chip pin 26 | source Table 4 (p.6); Table 3 (p.5) |
| RXD | Asynchronous data input (UART receive) | VIH 2.0 V min, VIL 0.8 V max | Comes from the target's TX; chip pin 25 | source Table 4 (p.6); Table 3 (p.5) |
| GND | Ground | Chip pin 3 | source Table 4 (p.6) | |
| VDD | 3.0-3.6 V supply input and the 3.3 V regulator output | 3.0-3.6 V | Chip pin 6 | source Table 4 (p.6); Table 8 (p.13) |
| REGIN | 5 V regulator input | 4.0-5.25 V | Chip pin 7 | source Table 4 (p.6); Table 8 (p.13) |
| VBUS | VBUS sense input, connected to the USB VBUS signal | Chip pin 8 | source Table 4 (p.6) | |
| D+ and D- | USB data lines | Chip pins 4 and 5 | source Table 4 (p.6) | |
| RST | Device reset: open-drain output of the internal power-on reset; an external source can reset the chip by pulling it low for at least 15 us | Chip pin 9 | source Table 4 (p.6) | |
| DTR and RTS | Data Terminal Ready and Request To Send control outputs, active low | Chip pins 28 and 24; can be left unconnected when unused | source Table 4 (p.6) |
Build with it
Project ideas for the CP2102 USB-UART board. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- ESP-01S programmer: The CP2102 UART runs at 3.3 V levels, which suits the ESP8266. Power the module from the stocked 3.3 V buck converter (fed from a 5 V source; check its output with a meter first), not from the adapter: the chip's regulator is rated only 1-100 mA and also feeds the chip. Join grounds between adapter, converter and module.
- GPS data logger: The GPS module's serial output goes to the adapter's RXD, whose input needs at least 2.0 V for a high; read it on the PC as a COM port. Learning project. The GPS module needs its own supply (check its voltage range on its own sheet) with grounds joined to the adapter; do not rely on the adapter's 3.3 V or 5 V pins, which are not documented.
- Pico serial console: The Pico's UART pins are 3.3 V, matching the CP2102 output levels; cross TX and RX and join grounds.
- ESP32 sensor logger: A second serial path keeps the ESP32's own USB free; the 3.3 V UART levels match the ESP32 pins.
Common mistakes
- Powering a hungry target from the adapter's 3.3 V: the chip's regulator is rated 1-100 mA and also feeds the chip itself, so WiFi modules and similar loads need their own supply (source)
- Wiring TX to TX: the chip's TXD is an output and RXD an input, so the adapter's TXD goes to the target's RX and its RXD to the target's TX, with grounds joined (source)
- Assuming 5 V signalling: the UART outputs swing to about VDD (3.3 V) and any I/O pin is rated 5.8 V absolute maximum, so do not feed higher levels into the UART pins (source)
Not covered by the official source
- The board is not covered by an official document: header labels, which regulator pins are exposed, and the exact chip variant (CP2102 or CP2102N) are unknown.
- Datasheet is the original CP2102 Rev 1.0 (10/04), mirror-hosted copy; the maker recommends CP2102N for new designs, so figures may differ on a CP2102N board.
- Later-revision tables (suspend current limits, RST thresholds) are not given on this page.
Sources
- link (Silicon Laboratories CP2102 Single-Chip USB to UART Bridge datasheet, Rev. 1.0 10/04)