Found on notebooks with serial port can output this circuit on the circuit board Protel PCB FT232A and MAX3245 have a schema file .. USBPCB3.PCB and usb1.sch schema files prepared by PROTEL99-SA
The USB to RS232 Dongle
Require extra Serial Ports on your new Laptop or PC? Would you like to add USB to your next project? With serial and parallel ports being phased out on new computers, hardware designers and hobbyists have no choice but to convert the USB port back to RS232 serial. FTDI have a very nice chip that does just that, the FT232AM. This chip converts USB to a standard high-speed serial port.
The bonus with FTDI is the drivers are already written for you. All you have to do is design the hardware and download the serial USB drivers from FTDI’s web site.
The schematic is quite simple, however the FT232AM requires a lot of external components to get it working. FTDI now have a FT232BM 2nd generation device. This device requires less external parts, therefore making it easier and cheaper to convert your old projects to USB!
source http://www.embedtronics.com/usb/usb232.html driver: http://www.ftdichip.com/FTDrivers.htm USB to RS232 Converter Circuit FT232AM MAX3245 alternative link:
Password: 320volt.com
Published: 2008/03/20 Tags: analog circuits projects
USB Port Audio Output
USB Port Audio Out USB Audio DAC project using the computer’s USB port can receive audio output source PCM2902 and used LP2951CM Eagle has PCM2902 Scheme and PCB files.
Circuit includes DAC, ADC, SPDIF output, input and HID part with 3 buttons for MUTE, VOL+ and VOL-. I used only DAC part. Other parts are not used. For high quality playback is needed to use external low-drop voltage stabiliser for DAC part. I used LP2951CM which was available at local store. Output voltage is set to about 3.7V with two resistors. Circuit board is designed regarding to good ground placement and separating of analog and digital ground. These ground are connected in one point at USB connector.
USB to AUDIO