
CH341 is a USB bus convert chip providing UART, parallel printer
port or synchronous serial with 2-wire or 4-wire through USB bus.
Besides that, CH341A also supports some common synchronous serial
such as 2-wire I2C/TWI (with SCL and SDA connection) or 4-wire
SPI (CS, SCK/CLK, MISO/SDI/DIN and MOSI/SDO/DOUT connection)
interface - this allows to use it as a very cheap I2C (24xx) or
SPI (25xx) flash IC programming interface.

Flash connection:

CH341A	dir	EEPROM

24	 >	SCL
23	<>	SDA

22	<	MISO
20	 >	MOSI
18	 >	SCLK
15	 >	~CS0
16	 >	~CS1
17	 >	~CS2

CS0-2 are the Chip Select lines; for making a programmer, you
need one of them connected to IC.

USB connection:

CH341A	USB
10	D+
11	D-



Taken from http://www.winchiphead.com/download/CH341/CH341DS1.PDF
