Showing posts with label usb. Show all posts
Showing posts with label usb. Show all posts
Thursday, September 18, 2014
USB Switch Schematic Wiring diagram Schematic
Anyone experimenting or developing USB ported peripheral hardware soon be comes irritated by the need to disconnect and connect the plug in order to reestablish communication with the PC. This process is necessary for example each time the peripheral equipment is reset or a new version of the firmware is installed. As well as tiresome it eventually leads to excessive contact wear in the USB connector. The answer is to build this electronic isolator which disconnects the peripheral device at the touch of a button. This is guaranteed to reduce any physical wear and tear and restore calm once again to the workplace.
USB Switch Schematic Circuit Image
The schema uses a quad analogue switch type 74HC4066. Two of the switches in the package are used to isolate the data path. The remaining two are used in a classic bistable flip-flop configuration which is normally built using transistors. A power MOSFET switches the power supply current to the USB device. Capacitor C2 ensures that the flip flop always powers-up in a defined state when plugged into the USB socket (‘B’ in the diagram).
The peripheral device connected to USB socket ‘A’ will therefore always be ‘not connected’ until pushbutton S2 is pressed. This flips the bistable, turning on both analogue gates in the data lines and switching the MOSFET on. The PC now recognises the USB device. Pressing S1 disconnects the device.
Circuit diagram :USB Switch Schematic Circuit Diagram
The schema does not sequence the connections as a physical USB connector does; the power supply connection strips are slightly longer than the two inner data carrying strips to ensure the peripheral receives power before the data signals are connected. The electronic switch does not suffer from the same contact problems as the physical connector so these measures are not required in the schema. The simple schema can quite easily be constructed on a small square of perforated strip-board.
The design uses the 74HC(T)4066 type analogue switch, these have better characteristics compared to the standard 4066 device. The USB switch is suitable for both low-speed (1.5 MBit/ s) and full-speed (12 MBit/s) USB ports applications but the proper ties of the analogue switches and perf-board construction will not support hi-speed (480 MBit/s) USB operation.
The IRFD9024 MOSFET can pass a current of up to 500 mA to the peripheral device with-out any problem.
http://streampowers.blogspot.com/2012/07/touch-switchs.html
Friday, June 6, 2014
Procyon – 80 MHz ARM Cortex M3 with SDRAM Ethernet SD USB
Procyon is a general purpose development board with special features for Ethernet, USB, and audio applications. It is based on Luminary Micro/Texas Instruments LM3S9x9x series of parts. The initial MCU is LM3S9B90.
The board contains the following features:
- 80 MHz, 100 Pin Cortex M3 Processor
- 16 MB SDRAM accessed on a 50 MHz EPI bus
- USB Host/Device/OTG port
- microSD card slot (Attached to SSI1/SPI1)
- 10/100 Ethernet
- I2S header for DAC output interface
- Up to 24 GPIOs available
- 3 UART, 2 I2C, 1 CAN, 2 SPI/SSI (one shared with microSD card)
- 10-bit ADCs
- General purpose timers: four 32-bit or eight 16-bit
- FTDI/Basic UART debug/program interface, on 16 pin GPIO/configuration header
- Three 10 pin headers for daughter boards
- 20 Pin JTAG Header
- User LED and User switch
Eridani – 50 MHz ARM Cortex M3 with USB
Eridani is a LM3S3651 based general purpose development board with USB Host/Device/OTG. You can buy one here. This documentation should help you use it effectively. All of the details on how to setup toolchains for this board are filed under getting started. [Link]
Saturday, September 28, 2013
USB Switch For Printers Circuit Diagram
This circuit switches a printer’s USB connection from a PC to a laptop. What was needed was a method of allowing a laptop to use the printer occasionally while at all other times the printer would be connected to the PC. Instead of unplugging the printer from the PC and then into the laptop, the circuit switches the USB connection automatically. K1 and K2 are standard type-B USB sockets, while K3 is a USB type-A socket. The USB lead from the laptop plugs into K2 while the PC’s USB lead plugs into K1. A USB cable from K3 connects the printer to this circuit. The cable from the PC is always plugged in while the cable from the laptop is only connected whenever this device needs to print. In normal operation the laptop is not connected to K2, so the USB signal to the printer comes from the PC via K1, the normally closed contacts of relay Re1, through to K3 and from there to the printer.
Circuit diagram:
Whenever the laptop is connected up, the presence of the 5-volt power signal on its USB port causes Re1 to switch over to the printer’s connection to K2 and the laptop. Unplugging the laptop returns control of the printer back to there PC. The circuit was tested on a USB 1.1 compliant printer and a PC and laptop that had USB-2.0 high-speed ports. The PCB traces for D+ and D– should be kept as short as possible and ideally should be the same length. The relay should be a low-power type (5 V at 100 mA coil current) with two changeover (c/o) contacts. Switch S1 is only required in situations where the two computers you want to select between are permanently present and connected up to the circuit. The switch then selects the computer having access to the printer.
Author: Liam Maskey - Copyright: Elektor Electronics
Wednesday, September 11, 2013
USB Function Generator Based on AD9833
One tool that I’ve been missing at my lab at home is function generator. They tend to be a bit expensive, so I haven’t bought one. I thought this might be a good opportunity to try and make one myself. I found a pretty common DDS (direct digital synthesis) chip, called AD9833. Then just strap a USB-enabled AVR micro there and maybe some analog electronics.
This board doesn’t do any of the special analog magic to allow for variable amplitude or offset for the signal. The output is fixed to 0-4v. I’m planning to make another completely analog board for adjusting amplitude and offset.
Subscribe to:
Posts (Atom)