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USB serial cable [pinouts]

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12 replies

by gergerdotcom

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i'm tryin' to figure how do I add another USB device of my computer ... can i use the serial COM ports and manage it to function if connected with a DB9 (male connector) and have it outs as USB port?

i see this item in the market but don't have idea how reliable or fast if used it and the complicity:)

12 replies

by robo_dev

The reason a db9 to USB converter costs $20-50 is that it has circuitry inside to do the protocol converison, voltage conversion, etc.

by gergerdotcom

what i'm tryin' to figure out is if i can manage serial COM ports to function if connected with a DB9 (male) and have it outs as USB port.

is purchaing the db9 to USB converter is the only solutions and no other way on how do I add another USB device to my computer if I am out of USB ports?

though i understand that its already available in the market but how reliable is the USB serial cable and its effectivity?

i'm planning to fabricate if i can do it myself so to learn also.

by oh smeg

These are slow and not overly reliable. The fact that they work only means that they =should be used as a Last Resort option.

You also can not plug any USB Powered Device to them as they do not have enough current available. They at best only have limited functionality.

Col

by oh smeg

It is possible to add 128 USB Devices per USB Port so I don't think that you will have exceeded each Ports limits but you do need to add a Hub to attach more than 1 USB Device per port and if you need more USB Ports you just Daisy Chain the USB Hubs till you have sufficient USB Ports available.

If you have High Powered Devices add a Powered USB Hub which is effectively the same as directly connecting to the M'Boards USB Ports.

Col

by computercookie

COM ports are slow compared to USB(I've seen some useless mobile phones that use USB ports to connect as COM ports whatever for I don't know).

Use a Hub, a lot cheaper than specialised cables.

by thechas

Here is a link to the USB cable pin-outs.

http://tinyurl.com/5rrf6x

However, it will not do you any good for what you need to do.

First, a standard serial port is WAY too slow to function as even a USB 1.0 port.

Second, as has been stated, the data standards are very different. Nor, can you be sure to have the 5 volt port power available from your serial port.

As has been stated in other answers, the easy way to add more USB ports to any system is to use a USB hub. I recommend a powered hub. That way, you don't risk trying to draw more port power than your PC can supply.

Another option, is to install a PCI USB card. Depending on the card, you can add up to 8 ports.

Chas

by gergerdotcom

hello all:)

thanks for all those who have contributed in my inquiries.

at least now i'm enlighted about USB serial cable [pinouts]. perhaps who knows their might be available in the market soon that has something to do booster to amplify if its not that fast to use USB serial cable being attach COM ports.

but if ever i'll really use the USB serial cable by attaching it to COM ports, do i have to used the "hyperterminal" to change settings or no need?

cheers!

by thechas

I think we are loosing something in the translation between our languages.

You will NEVER be able to run a standard USB device from a standard computer COM port.

Not only are there differences in the signal levels and the USB required device power, the data transfer rates and the data word structure are different between a COM port and a USB port.

Connecting a COM port to a USB device would be similar to using a motor scooter in place of one of the jet engines on a 747 airliner. While there is a base similarity, you cannot substitute one for the other.

There are only 2 ways to add USB ports to a computer.

Install a USB controller card.

Connect a USB hub to an existing USB port.

There is not way to have a functional USB interface that would connect to a computer through the COM port.

Chas

by gergerdotcom

hi Chas:)

thanks really for giving me the clear picture. now, i can say that i still need additional stuff related to all these.

cheers!

by robo_dev

The basic concept is that if you can connect with a $2 cable, it's the same protocol.

A Serial to USB interface converter costs $50 because there's a logic chip, software drivers, and protocol conversion going on. The complexity drives the cost.

You cannot bolt wings on a car and make it fly.

You cannot graft gills on a bird and have it swim underwater.

You cannot solder a DB9 connector to a USB cable and expect +5V and the correct USB signals to come out the other end...

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