Introduction

The USB-Serial interface presented here is based on the FT232RL integrated circuit from FTDI. The interface consist simply of the component itself and a few capacitors. The used connector is a USB MINI-B type. A total of five components is necessary to realize the interface. However, the possibilities of the interface are amazing, indeed the characteristics of the FT232RL are the following ones:

• UART interface support for 7 or 8 data bits, 1 or 2 stop bits and odd/even/mark/space/no parity. Fully assisted hardware or X-On/X-Off software handshaking.

• Data transfer rates from 300 baud to 3 Megabaud (RS422/RS485 and at TTL levels) and 300 baud to 1 Megabaud (RS232)

• Auto transmit buffer control for RS485 applications

• Transmit and receive LED drive signals.

• New 48MHz, 24MHz,12MHz, and 6MHz clock output signal Options for driving external MCU or FPGA

• Integrated 1024 Bit internal EEPROM for storing USB VID, PID, serial number and product description strings

•  Each device is assigned a unique number which is burnt into the device at manufacture. This ID number cannot be reprogrammed by product manufacturers or end-users. Then the chip can be used as a dongle to protect software.
  

• True 5V / 3.3V / 2.8V / 1.8V CMOS drive output and TTL input

• Synchronous and asynchronous bit bang mode interface options with RD# and WR# strobes allow the data bus to be used as a general purpose I/O port

• Dricers for Linux, Win98, ME, 2K, XP, XP64, Embedded XP, Server 2003, MAC OS-8-9-10 et WinCE

• Royalty-Free librairies and DLLs to use the chip
  

Moreover, C++ software with source code are available on this website

Schematic

The figure 1 shows the module schematic. On the left, one find the USB MINI-B connector, the FT232RL chip is on the middle like the three capacitors. On the right are the inputs/outputs pin of the DIP20. To do the circuit working is very simple: with an appropriate USB cable (A to MINI-B), connect the module to a PC USB port. Install the necessary drivers given in appendix (or from the FTDI website) and that's all. A simple C++ software with source code is given hereafter in order to play with the module.

PCB

The figure 2 show the two faces of the PCB. The top layer is on the top of the figure. On the bottom layer, one can see the place for the USB MINI-B connector (on the left), here is a photo of this connector: .

It's mechanical drawing can be found here: mechanical drawing.

In appendix, one will find the Gerber files of the project. All these files can be analyzed before the realisation of the PCB thanks to the free Gerber viewer GC-Prevue.

Réalization