CP2104

@@ -0,0 +1,67 @@+# CP2104++**Silicon Labs** · USB-to-UART bridge · QFN-24++Turns a USB port into a serial UART so a host sees a virtual COM port and the board gets TXD/RXD plus modem control lines. It handles USB 2.0 full-speed and UART rates up to 2 Mbps, and integrates the oscillator, voltage regulator, and a configurable EEPROM for the USB descriptors, so the external parts are just decoupling. Four GPIO pins add status LEDs or control. A compact, self-contained alternative to the FT232 and CH340 for USB serial.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | RI | input | Ring Indicator control input (active low). Modem-status handshake line. |+| 2 | GND | power_in | Ground reference. Must be tied to ground. |+| 3 | D+ | bidirectional | USB D+ full-speed (12 Mbps) differential data line. Connect to the USB connector D+ pin. |+| 4 | D- | bidirectional | USB D- full-speed (12 Mbps) differential data line. Connect to the USB connector D- pin. |+| 5 | VIO | power_in | I/O supply voltage input. Sets digital I/O rail from 1.8 V up to VDD. Decouple to GND. |+| 6 | VDD | power_in | Digital core supply (3.0 to 3.6 V). Also the output of the on-chip 3.45 V voltage regulator when REGIN is driven from VBUS (self- or USB-powered). Decouple to GND. |+| 7 | REGIN | power_in | 5 V regulator input (3.0 to 5.25 V). Input to the on-chip 3.45 V LDO whose output appears on VDD. Typically tied to VBUS. |+| 8 | VBUS | input | VBUS sense input. Connect to the VBUS signal of the USB connector so the device can detect bus attach (2.5 V threshold). |+| 9 | RST | bidirectional | Device reset (active low). Open-drain output of internal POR / VDD monitor; may also be driven low externally for at least 15 us to initiate a system reset. |+| 10 | NC | unconnected | No connect. Leave floating or tie to VIO. |+| 11 | GPIO.3 | bidirectional | User-configurable digital I/O. Supply is VIO (1.8 V to VDD). May be left unconnected when unused. |+| 12 | GPIO.2 | bidirectional | User-configurable digital I/O; optional RS-485 transceiver bus-control output (Section 7.2). Supply is VIO. |+| 13 | GPIO.1 | bidirectional | User-configurable digital I/O; optional receive-toggle output (Section 7.1). Supply is VIO. |+| 14 | GPIO.0 | bidirectional | User-configurable digital I/O; optional transmit-toggle output (Section 7.1). Supply is VIO. |+| 15 | SUSPEND | output | Active-low USB suspend indicator. Driven low while the CP2104 is in the USB Suspend state. |+| 16 | VPP | passive | OTP ROM programming supply pin. Connect a 4.7 uF capacitor between this pin and ground to support ROM programming via the USB interface. During programming VPP is 5.75 V to VIO+3.6 V. |+| 17 | SUSPEND | output | Active-high USB suspend indicator. Driven high while the CP2104 is in the USB Suspend state. |+| 18 | CTS | input | Clear-To-Send hardware flow-control input (active low). Modem handshake line. |+| 19 | RTS | output | Request-To-Send hardware flow-control output (active low). Modem handshake line. |+| 20 | RXD | input | Asynchronous UART receive data input. Data rates 300 bps to 2 Mbps; 5/6/7/8 data bits; 1/1.5/2 stop bits; odd/even/mark/space/no parity. |+| 21 | TXD | output | Asynchronous UART transmit data output. Data rates 300 bps to 2 Mbps; 5/6/7/8 data bits; 1/1.5/2 stop bits; odd/even/mark/space/no parity. |+| 22 | DSR | input | Data-Set-Ready modem control input (active low). |+| 23 | DTR | output | Data-Terminal-Ready modem control output (active low). |+| 24 | DCD | input | Data-Carrier-Detect modem control input (active low). |++## Key specifications++| Parameter | Value |+|---|---|+| Type | USB-to-UART bridge |+| USB | USB 2.0 full-speed |+| UART data rate | 300 bps to 2 Mbps |+| GPIO | 4 configurable |+| Integrated | Oscillator, regulator, EEPROM |+| Supply | VBUS or self-powered (3.0-3.6 V core) |+| Package | QFN-24 (4x4 mm) |++## Ordering variants++- `CP2104-F03-GM (QFN-24)`+- `CP2104-F03-GMR (QFN-24, tape & reel)`++## CAD (KiCad official)++- Symbol: `Interface_USB:CP2104 (KiCad official)`+- Footprint: `Package_DFN_QFN:QFN-24-1EP_4x4mm_P0.5mm_EP2.6x2.6mm`+- 3D model: QFN-24 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Silicon Labs datasheet](https://www.silabs.com/documents/public/data-sheets/cp2104.pdf) (22 pp, sha256 `9569257991f26467`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/cp2104-datasheet.pdf)

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