Lowest Cost solution to split USB Port
william chan
Posts: 1,326
Hi,
For my next project, I need 2 USB connections to a PC.
But I only have one USB cable to the PC.
So, I am thinking, the most logical way is to embed a USB HUB IC on my board.
Unfortunately, most USB Hub ICs splits to 4 ways wheares I only need to split 2 ways.
Can a USB connection by split using discrete components?
What is the lowest cost USB Hub IC available in the market?
Anybody has experience in this?
Thanks.
For my next project, I need 2 USB connections to a PC.
But I only have one USB cable to the PC.
So, I am thinking, the most logical way is to embed a USB HUB IC on my board.
Unfortunately, most USB Hub ICs splits to 4 ways wheares I only need to split 2 ways.
Can a USB connection by split using discrete components?
What is the lowest cost USB Hub IC available in the market?
Anybody has experience in this?
Thanks.
Comments
I suppose the chip has to capture, buffer, and split addresses.
Also.......The Propeller has code to support a USB Host that might provide some insight.
http://zipdf.com/usb_hub_chip
or a PropPlug?
https://www.google.com/search?q=dual+usb+cable&rls=com.microsoft:en-US:IE-Address&tbm=isch&imgil=dR3ga8pLQDIeDM%3A%3Bhttps%3A%2F%2Fencrypted-tbn0.gstatic.com%2Fimages%3Fq%3Dtbn%3AANd9GcTHQttb2toRr4LBNWCF6twic6eyTqXESc5V7JefPTpEVlPhKJP1kw%3B250%3B194%3BrxcbClAVGeL86M%3Bhttp%3A%2F%2Fwww.dd-wrt.com%2Fwiki%2Findex.php%2FLaFonera_Hardware_Power_from_USB&source=iu&usg=__GPwUtJxPYysBt4utYvKYwHWvUTk%3D&sa=X&ei=zWZRU8eQGtGKyAS7nIL4BQ&ved=0CEkQ9QEwAQ#facrc=_&imgdii=_&imgrc=mqWU_sUUvAp2RM%3A%3B61Of9FrjEAQ_QM%3Bhttp%3A%2F%2Fs291058909.onlinehome.us%2Flist%2FUSB%20Cable%2FA205.jpg%3Bhttp%3A%2F%2Fwww.ebay.com%2Fitm%2FNew-USB-2-0-Female-to-Dual-USB-A-Male-Power-Y-Cable-%2F170626508871%3B421%3B364
EDIT: Third black picture. Would that work for you?
All the cables I've seen like this are "vampire" cables for power purposes. If you have a USB peripheral that is going to draw more than 500ma, you can use these to get over the 500ma per port limits. Your PC sees the power draw split across two ports.
I got the impression that the OP was looking for a way to add 2 USB ports to a board - you'd have one cable coming from the PC but there would be hardware on the project board that would enumerate as only 2 ports (like a mini-mini-hub) on the project board. How many discrete components does it take to build a USB port if it can be done?
What's the cheapest solution? I suspect Ebay has it. I guess you could just buy something and remove the case, and mount it to your board.
What would I do? I'd probably consider adding a card to the PC to provide 4 more USB ports and use two cables.
Ummm... that dual cable is likely just to get more amps out of two Host ports for device that needs more than one USB port can provide. I suspect it doesn't have any hub function..
FTDI does seem to have a USB to dual serial chip that might be what he really desires.
I expect descrete components are not an option. After all, people have been working on USB Host and Client services with a Propeller. It seems to require a processor (this is why I hate USB and love RS422/RS485).
http://www.ftdichip.com/Products/ICs/FT2232H.htm
http://www.ebay.com/sch/i.html?_nkw=usb+hub
William, I think you will find that it is much simpler and less expensive to buy one of the small hubs that are available for a few dollars. The case for some of them is not much larger than the space for USB connectors, and removing the board to use without the case makes it even smaller.
Yes, split into 2 ports. One port is to connect to a USB camera and another port for maybe a FTDI chip which can use it's GPIO pins to control a LCD display.
The customer is looking for 3,000 pcs of the product, so visiting a local computer shop and asking for 3,000 pcs of USB Hubs is not feasible. : )
The Hub IC has to be low cost, minimal number of pins and highly available.
My gut feeling is that all the chips splite to 4 hubs. You'd just wire up two and leave two unused.
When searching DIY usb hub, I get funky builds with chips
http://www.instructables.com/id/Four-port-USB-hub/
http://www.lvr.com/usb_device_hardware.htm
Or switching form one to the other and Windows will give you the pings sound as it think it lost the connection and gain another one.
(though doing that 200 a day probably will crash windows evidently as it always seems to get stack overflow etc)
Switch: the ftdi gpio could switch it to usb, but how would you switch it back to ftdi, I guess you have to tell the mcu do it.
http://www.ti.com/product/ts3usb221
2/3 port hub
http://www.ti.com/product/tusb2036
Here is a 2port usb3.0 hub chip
http://www.ti.com/product/tusb8020b-q1
OK, that puts it into a whole new category. Perhaps you could buy a single low cost unit and crack it open to see what chip is used.
But the chip has to support USB 2.0 High Speed. ( 480Mbps )
http://www.microchip.com/wwwproducts/Devices.aspx?product=USB2502#documentation
Maybe one will fit your requirements.
You have to love late-arriving critical bits on information...
Up until this new info, the FTDI VNC2 would be the ideal
http://www.ftdichip.com/Products/ICs/VNC2.htm
You may want to contact FTDI, and ask them for lead times on the FT900 ?
http://www.ftdichip.com/MCU.html
Interesting looking chip, they suggest USB2512B as a replacement, and that looks low cost ($1.38/100+)
also says
["The SMSC hub supports lowspeed, full-speed, and hi-speed (if operating as a hispeed hub) downstream devices on all of the enabled downstream ports."]
So a pairing like [USB2512B + CP2105] would give High Speed pass thru, and two Serial Ports / GPIO work.
Why do you prefer the CP2105 over the FT230X chip? Is it better?
Can the QFN chips like USB2512B be easily soldered by hand?
The CP2105 has dual UARTS, which can be very useful, and I think is slightly lower cost than FT230X, but they are broadly similar. (USB-UARTS, with fine grained Baud choices)
I admit the QFN package is less low-volume friendly.
If you make the PCB PADS a little longer than normal, and even pre-tin the QFN, then there is usually enough thermal path for a standard fine tip iron to work quite well.
For the centre PAD, a larger central hole can give you soldering access.
-Phil
This one is pretty cool.
reading further I have to chuckle...GL850G also support both Individual and Gang modes ...
aha. Gang modes. And we worry about CORES as name for COGs?
Enjoy!
Mike