CH340 USB To Serial Converter IC

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CH340 USB to Serial Converter IC 8 October 2021 - 0 Comments

CH340 USB to Serial Converter IC

CH340 IC Pinout

The CH340 is a popular IC that is a bidirectional USB to Serial converter IC, used to convert USB signals into UART, which can be used to communicate with microcontrollers. This IC is found in some versions of the Arduino Nano to perform Serial to USB conversion to communicate with the board through a USB connector. This article will focus on the CH340T variant of the IC, which is used for UART to USB conversion.

CH340 Pinout Configuration

Pin Number	Pin Name	Description
1	CKO	Clock output
2	ACT	Negative phase clock output
3	TXD	Serial data output
4	RXD	Serial data input
5	V3	External 3.3V supply
6	UD+	USB data positive
7	UD-	USB data negative
8	GND	IC ground reference
9	XI	External crystal pin
10	XO	External crystal pin
11	CTS	Clear to send signal pin
12	DSR	Data set ready pin
13	RI	Ring indicator pin
14	DCD	Data carrier detect pin
15	DTR	Data terminal ready pin
16	RTS	Request to send pin
17	NC	Not connected
18	R232	RS232 enable
19	VCC	Power input
20	NOS	Forbid USB device suspending pin

Features & Specifications

Full speed USB 2.0
Emulates standard serial interface, can be used to upgrade older equipment to USB
Baud rate from 50bps to 2Mbps
5V and 3.3V power
SSOP-20 package

Note: Complete technical details can be found in the CH340 datasheet linked at the end of this page.

CH340 Equivalents

FT232, CH340G

Other USB To Serial ICs

CH341, FT232

How To Use CH340 USB To Serial Converter IC

The CH340 is an easy-to-use USB to serial IC that converts USB signals to UART, which is used to communicate with microcontrollers and older appliances.

One of the most common applications of this chip is in various Arduino and Arduino-compatible boards, since the ATMega329P used does not have built-in USB support, it talks to a computer using a UART interface that is converted to USB using the CH340.

ATMega328P Microcontroller with CH340 Circuit Diagram

Shown in the above figure is the ATMega328P microcontroller and the CH340 connected together to provide a USB interface.

The TX and RX serial pins are connected to pins PD0 and PD1 of the microcontroller respectively, providing the data connections on the UART side. Another interesting thing to note is that the DTR pin is connected through a capacitor to the reset pin, which resets the microcontroller every time a serial connection is established or the USB connector is plugged in. On the USB side, the D+ and D- pins are connected to the respective pins on the USB connector. A 12MHz crystal is also connected (along with its load capacitors) to provide a USB clock. With this simple circuit configuration, the CH340 can be used as a simple USB to the serial interface.