Part Number: CH340
Function: USB to serial chip
Package: SSOP-20 Type
Manufacturer: WCH ( http://wch.cn/ )
This post explains for the semiconductor CH340.
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Description
CH340 is a USB bus convert chip and it can realize USB convert to serial interface, USB convert to IrDA infrared or USB convert to printer interface. In serial interface mode, CH340 supplies common MODEM liaison signal, used to enlarge asynchronous serial interface of computer or upgrade the common serial device to USBbus directly. More detail about USB convert to printer interface please referring to the second manual CH340DS2. In infrared mode, add infrared transceiver to CH340 can compose USB infrared adapter, realize SIR nfrared communication. The CH340 chip can be used with a variety of programming languages, including C, C++, Python, and others.
CH340 Pinout
Features
1. Full speed USB device interface, conforms to USB Specification Version 2.0, only needs crystal and capacitance external.
2. Emulate standard serial interface, used to upgrade the former peripheral device, or add excess serial interface through USB.
3. Totally compatible with serial application program in computer endpoint Windows operation system.
4. Hardware full duplex serial interface, set transceiver buffer, supports communication baud rate varies from 50bps to 2Mbps.
5. Supports common MODEM liaison signal RTS, DTR, DCD, RI, DSR and CTS.
6. Through adding level converter equipment to supply RS232, RS485, RS422 and other interface.
7. Supports IrDA criterion SIR infrared communication, supports baud rate varies from 2400bps to
115200bps.
8. For it is through USB converts to serial interface, only compatible with application layer not totally.
9. Software compatible with CH341, using drive of CH341 directly.
10. Support 5V and 3.3V source voltage.
Block Diagram
Function description
CH340 sets up USB pull-up resistor internal, UD+ and UD- must be connected to USB bus.
CH340 set power up reset circuit. RSTI is used to input asynchronous reset signal from outside.
When RSTI is high-level, CH340 chip is reset. When RSTI is low-level, CH340 will continue delay 20mS to reset and then step into normal work state. In order to reset credibly during power up period and weaken the disturber from outside, a 0.47uF capacitance between RSTI and VCC is recommended.
When CH340 chip is working normally, the outside must supply 12MHz clock signal to XI pin.
In generally, clock signal is generated by inverter in CH340 through oscillating of crystal keeping frequency. A crystal of 12MHz between XI and XO, XI and XO connect a high frequency oscillator capacitance to ground respectively can compose the peripheral circuit.
Reference Site: https://www.sunrom.com/m/4511
Other data sheets are available within the file: CH340G, CH340R, CH340T
CH340 Datasheet
