--- WORK IN PROGRESS! ---
In this page you can find a set of useful circuits that you may need to develop your project. Most of them are designed using CadSoft EAGLE PCB and can be printend in our lab without the need of an external PCB supplier.
USB - Serial adapter
This is an FTDI FT232RL based USB - Serial adapter you can use to access serial devices (0-5V levels, NOT RS232) via a standard USB port. At one side of the circuit there is a mini-USB connector, while at the other side you can find a pin header with 6 contacts:
|4||3.3V output from FT232RL|
|5||serial level select (3.3V / 5V)|
|6||5V output from USB connector|
You must connect pin number 5 to pin number 4 (3.3V) OR to pin number 6 (5V) to select the voltage levels of the serial port. If you leave pin number 5 disconnected the adapter will not work.
Here you can download the schematics and the PCB layout: FT232RL.zip
USB - Serial adapter (insulated variant)
This is the same USB - Serial adapter circuit you can find above, with the addition of a [ADUM1201 http://www.analog.com/en/ADUM1201/productsearch.html] digital insulator than makes the USB port and the serial port completely insulated. Also the grounds are separated, so you should interface to your circuits without damage risk for your computer (no guarantees at all - use at your own risk ;-). In this variant, you have to provide the power supply for the serial-side of the insulator, that works at 3.3V as well as at 5V. So, the pinout of the serial connector is:
|4||serial level select (3.3V / 5V)|
Here you can download the schematics and the PCB layout: FT232RL-ADUM1201.zip
USB - Serial adapter (iRobot Roomba variant)
This is a variant of the USB - Serial adapter designed to interface with iRobot Roomba robots. In this circuit the serial level is imposed at 5V, as the Roomba serial port works at that voltage, and the PIN #4 of the serial connector is wired to RTS signal, that you can use to wake the Roomba or to switch the baud rate (see Roomba interface specifications for details). These pins need to be connected to the DIN-8 serial connector of the Roomba, following the scheme shown on the Roomba interface manual.
The pinout of the serial connector is:
Here you can download the schematics and the PCB layout: FT232RL-roomba.zip