Here I want to present results to use a very cheap USB to I2C- Bus chip CH341A. You can by this chip drirectly via ebay, search with keywords USB I2C. This is the product screenshot:
This part comes completely without any documentation. In FH Lübeck we worked out this connector using some sources coming from internet and finally we got a small document and a C# application software with source code presented on this page. The document is in German, but source code can be used in any language. We can access with this chip several examples of I2C- chips like ELV- 4- digit- display to display four digit numbers using chip SAA1064, the read out of a temperature sensor MSP9801, the digital to analog DAC- chip MCP4725 and the analog to digital ADC- chip ADS1015. The I2C- speed can be changed from 100 kHz to 750 kHz.