Accidentally I found one pretty interesting chip from FTDI: FT4232HL. This manufacturer is quite well known by it's USB<=>Serial solutions and their "driver" war against chinese clones. Nevertheless, this problem has a solution, so I will not go into the details.
FT4232HL is a 4-channel USB<=>Serial converter, which also supports I²C, GPIO and SPI modes. These features are the subject of the separate article, by default device works in the USB<=>Serial mode, which is more than enough for me.
The chip is quite small, but can be soldered with more or less good soldering iron without any problems. It does not require a lot of additional components, but PCB layout is pretty critical for the high-speed USB devices, power decoupling capacitors should be right near the corresponding pins, so I decided to make a small PCB for this chip.
So, here is the schematic:Figure 1: Adapter schematic
The schematic is quite simple and is almost completely copy-pasted from the datasheet. I wanted to have a data transfer indication for each channel (I like blinking LEDs :)), so the appropriate part from the documentation was also implemented. If you think that you don't need it - please think once again. These several LEDs can save you a lot of the debugging time.
Several days I was busy with the 3D models of all the components, and finally the board was implemented. Manufacturing was ordered at the Seeed Studio, in order to save costs this PCB was ordered together with several others, so was cutted manually after the manufacturing. Assembly was done manually as well. Here is the 3D model of the board:Figure 2: 3D model of the board
And here is the real board:Figure 3: Real board
On the photo you can see the first version of the PCB, which has wrong PCB connector pinout. In this post I publish the corrected version.
The adapter works right after the first power-on, I do not have any problems with it.
KiCAD project is here.
KiCAD libraries, which were used in this and other projects, are on the GitHub.