SPI example for CH341 USB adapter

Here is working SPI example for CH341 USB adapter. This example uses 2x D flip-flop to make 2-bit shift register (2-bit "delay" on output)

Circuit schematic is below:

Requirements

Hardware:

• you need CH341A USB to UART/IIC/SPI/TTL/ISP adapter EPP/MEM Parallel converter I got my from Amazon.de as DollaTek CH341A USB zu UART/IIC/SPI/TTL/ISP Adapter EPP/MEM Parallelwandler. If you never used this module please see my article Getting started with LC CH341A USB conversion module
• parts required to create above Sample Circuit - see schematics

Software:

• Windows OS - I tested this project on Windows XP SP3 guest in VirtualBox
• Visual Studio 2010 (This it the last version supported on XP SP3)

Setup

The CH341A adapter must be setup following way:

• jumper set to I2C/SPI mode
• voltage set to 5V TTL logic (this is because used CD4013 D Flip-Flop would be near by required minimum voltage in case of 3.3V and too slow)
• please see picture below for correct configuration:

Software setup:

• Download and install CH341PAR.ZIP - USB driver for CH341 chip in Parallel mode (EPP, MEM). This driver is valid also for I2C mode and SPI mode (yes - even when it is marked parallel).
• install VisualSutdio 2010

Create environment variable CH341_SDK that should point to extracted CH341PAR.ZIP header and library files. For example if you have extracted file:

C:\CH341_DRIVER\LIB\C\CH341DLL.H 

Then your CH341_SDK should be set to C:\CH341_DRIVER\LIB\C.

Open and rebuild solution TestSPI_VS2010/ch341_spi_shiftreg.sln in VisualStudio 2010. There should be no errors.

Connect your CH341A USB module to target circuit. Following pins are used:

PIN Name	Direction	Description
GND	N/A	Common ground
VCC	N/A	5V supply
MISO	Input	master in slave out - SPI
MOSI	Output	master out slave in - SPI
SCK	Output	master clock - SPI
/CS0	Output	Chip select 0, active in Low 1

---

1. The /CS0 signal is currently used by Logic Analyzer only (not connected to test circuit)

NOTE: Direction is from CH341A USB Module "view".

Connect your CH341 USB module to your PC. There should be permanently lighting red LED on USB module.

When you run example program you should see output like:

CH341 SPI shift register example
CH341 version: 33
Device 0 name is '\\?\usb#vid_1a86&pid_5512#5&18f54cb7&0&1#{5446f048-98b4-4ef0-9
6e8-27994bac0d00}'
Opening device# 0
Sending to SPI:
Index=0, Value=0xaa
Index=1, Value=0x55
SPI returned back data:
Index=0, Value=0x6a
Index=1, Value=0x95

And LED D1 should be ON.

NOTES: 1st and 2nd bits of returned data can be different than as shown in above listings - because these are values from two previous clock ticks (or should 0 after CD4013 reset)

Output

Here is output from PulseView:

Please see yellow arrows - how the data are exactly shifted by 2 bits - thanks to these 2 D Flip-Flops working as 2-bit shift register.

And here is also /CS0 signal (not used in this circuit) - only start shown (I used while(1){ CH341StreamSPI4(); Sleep(10);} loop to generate data for Logic Analyzer):