USB hard wiring. - Page 1
Forum section: electronics / general

author: G7PSK
author_rank: Super Contributor
timestamp: May 31, 2012, 07:28:54 pm
content: I want to install what is basically a piece of usb connected hard ware inside a laptop, I was thinking of hard wiring it by removing the usb socket on it ans soldering the wire direct to it and the other end to the back of a usb port on the motherboard will this cause any problems do you think.

author: IanB
author_rank: Super Contributor
timestamp: May 31, 2012, 07:35:37 pm
content: I would imagine it will work as long as you take care of signal integrity. In other words use the correct cable and keep the non-cable interconnects as short as possible.

author: SeanB
author_rank: Super Contributor
timestamp: May 31, 2012, 07:44:24 pm
content: No problem, as long as you are comfortable with not using that socket on the laptop again. If there is a Wifi card then the riser has a USB d+ and d- pad that is probably unused, or you can lose the internal camera and use the 2 data wires for the device. you will need to get 5V and ground from somewhere though, as normally a usb internal webcam has a switched power rail.If you get a service manual for the laptop you will probably find there are unused USB ports on the chipset.I did this with my EEEPC, to add extra USB memory, using the internal camera port ( Where I found out about the power switching so went to the board to get 5V) and the unused riser usb connections to add 2 flash drives stripped of housing and connectors into the casing. I used 24AWG network cabling to wire them in, and taped them down to assorted patches of board where they would fit.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: May 31, 2012, 10:34:18 pm
content: Use twisted pair for the data lines. I saw one guy who had no success doing something similar until he twisted the data lines together.

author: Psi
author_rank: Super Contributor
timestamp: June 01, 2012, 12:49:51 am
content: If you have a google you should be able to find other people that have done this.I remember reading about someone who put usb wifi, usb bluetooth and usb 3G module inside a tiny laptop that had neither.

author: amyk
author_rank: Super Contributor
timestamp: June 01, 2012, 07:15:16 am
content: Quote from: Jon Chandler on May 31, 2012, 10:34:18 pmAlso keep the D-/D+ pair as close in length as possible. Low speed and full speed are reasonably tolerant of mismatched lengths, but the tolerances for high speed are much tighter. It also depends on the devices --- I've noticed lesser-known Chinese USB chipsets seem to have bigger tolerances with respect to matching the lengths, but at the same time are more susceptible to random bit errors: sometimes you'll get intermittent behaviour where it seems to work most of the time but randomly disconnects or corrupts data.

author: G7PSK
author_rank: Super Contributor
timestamp: June 01, 2012, 07:47:12 am
content: Thanks for the info, all. I have connected to the back of the usb socket as although I have the circuit diagram and service manual the only other break in point I could find is the port replicator socket and the wires and tracks are so small and close together that it would be very difficult to make a connection. The laptop in question is a Panasonic CF28 circa 2002 there is only one usb fitted if I find that the usb will not work with the wiring connected to the other equipment (a usb oscilloscope, I hope to make a touch screen super tough oscilloscope) I will most likely just fit a switch.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: June 01, 2012, 12:45:30 pm
content: Quote from: G7PSK on June 01, 2012, 07:47:12 amDo you mean more than one USB device connected to the same USB port at the same time? That's definitely not going to work!

author: Unknown
author_rank: Unknown
timestamp: June 01, 2012, 02:48:21 pm
content: Just use a bus-powered hub and stop treating USB like a DC/audio frequency circuit. Running fast differential signals through a switch (connecting multiple devices to the same port is definitely not going to work) designed for DC/mains sounds like a signal integrity nightmare. There will be an impedance mismatch, and the two signals are not going to be tightly matched. You may be able to fit the hub internally if you're creative.

author: G7PSK
author_rank: Super Contributor
timestamp: June 01, 2012, 03:01:57 pm
content: I had thought about a hub and it may be the way I go but having removed the GPRS board in order to make room for the new board I looked at the circuit diagram again there is a USB+ and - onthe connector and a 5 volt as well. the only problem that in order to make a connection I need to break into a ribbon wire that has 50 wires in and is only 25.53mm wide what I don't know is are the wires copper or aluminium, the connectors are the usual sort of clamp things that are used in computers and I need to be able to solder.

author: SeanB
author_rank: Super Contributor
timestamp: June 01, 2012, 03:06:18 pm
content: Check the chipset, there are bound to be unused usb ports.

author: amyk
author_rank: Super Contributor
timestamp: June 02, 2012, 11:10:09 am
content: Quote from: SeanB on June 01, 2012, 03:06:18 pmAlthough they may not be brought out from the pins/balls, and disabled by firmware or strapping options.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 02, 2012, 11:41:50 am
content: i used very long big "mains cable" connecting my remote USB device (2 of em in pair, since mains only 3 core usb 5), worked like a charm, but i got warning "sorry, Windows unable to use full speed potential of this device"

author: G7PSK
author_rank: Super Contributor
timestamp: June 02, 2012, 04:26:28 pm
content: I have found another usb point I can use the only problem is that the connections are only 0.3 mm wide with 0.25 mm between the tracks I am not sure if I will be able to attach to these due to the small size, I am used to working with somewhat larger stuff these days.What is the best way to make connections by hand at this small a scale.

author: SeanB
author_rank: Super Contributor
timestamp: June 02, 2012, 05:46:51 pm
content: Fine tipped soldering iron and 36SWG wire, with a pretinned tip cut to a 1mm length. Then after soldering you can place a drop of superglue over the soldered joint, and another nearby to hold them down. A small piece of veroboard 2 by 2 holes then can be used as an anchor, and allows thicker wire to be attached, then glue the board down. I did this years ago on my alarm clock, and it still is in use 20 years later.