FTDI HARDWARE INTERFACE
An FTDI-integrated circuit has the two interfaces (USB and UART) (as shown in Figure 44-2). As per typical UART devices, serial signals are only at TTL or 3.3v levels, not RS232 voltage levels. This means that the UART can directly interface with a microprocessor UART. An FDTI device such as the FT232R would typically integrate into a microcontroller system to implement a USB interface for the system. This would enable the target system to directly connect to a computer system via that system’s USB host. The USB interface is implemented, as shown in Figure 44-3. The FT232B UART interface would be directly interfaced to the UART interface of a microcontroller, as shown in Figure 44-4.
A USB to Serial cable can be implemented using the device. The FT232R UART signals would be level shifted to RS232 levels via a MAX232 device, as shown in Figure 44-5. The other RS232 modem signals, such as DTR, DSR, DCD, can be similarly implemented.
The simplest use of the FTDI technology is as a USB to Serial cable (refer to Figure 44-4). The EasySync Ltd USB-RS232 Adapter Cable is an example of such a cable. Install the FTDI ...