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Topic: Help creating USB Serial CA-42 Cable

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Hi everyone,

I am trying to create a cable as above. I ordered a clone CA-42 from ebay and did some testing with a multimeter, I seemed to have 2 VCC's so I opened it up and to my surprise I found 2 wires soldered to a single point on the PCB, there are 4 wires total so I expected to find a VCC, GND, TX & RX.

Below is a picture with the 2 wires unsoldered, they were on the furthest point on the right.

I just need to know does this look right to anyone else? should those wires have been there? I haven't had experience with this before and some help would be really appreciated

http://s1143.photobucket.com/albums/n64 … 777/CA-42/

Thanks a lot

Not sure, but you don’t need VCC anyway, only the other three. The Wiki gives these identification instructions.

Once found, you can easily check where is the GND, which is connected to the same ground layer than the power connector. The VCC should be fixed at 3.3V and connected to the supply layer ; the TX is also at 3.3V level, but using a multimeter as an ohm-meter, if you find an infinite resistance between the TX and VCC pins, it means they're distinct signals (else, you'll need to find the correct TX or VCC pin). The RX and GND are by default at 0V, so you can check them using the same technique.

And similarly again here:
http://wiki.openwrt.org/doc/hardware/po … ter.method

(Last edited by towolf on 20 Mar 2012, 20:59)

Thanks towolf! smile I should mention that I am looking to do this:

http://forum.nas-central.org/viewtopic. … amp;t=5145

I have just noticed that on the underside of the board exactly where the 2 cables were there is another point labelled "3v" I measured it and it came out at 3.6v

So I connected it to the serial header my NAS along with GND, TX and RX but nothing :'( I guess im just going to have to keep trying.

Thanks

Did you remember to flip RX and TX? RX on one side goes to TX on the other and vice versa.

Hi,

yeah I tried TX and RX both ways as it is easy to mix them up but no joy sad I have ordered a DKU-5 cable from ebay to see how thats wired and will try with that when it arrives.

Il post pics of that too for reference

Cheers

CreepyBloke wrote:

Hi,

yeah I tried TX and RX both ways as it is easy to mix them up but no joy sad I have ordered a DKU-5 cable from ebay to see how thats wired and will try with that when it arrives.

Il post pics of that too for reference

I got this thing last week on Amazon, and it’s pretty cool.
www.elv.de/Mini-USB-Modul-UM2102,-Komplettbausatz/x.aspx/cid_74/detail_10/detail2_28776


http://i.imgur.com/zL6OYl.jpg

(Last edited by towolf on 21 Mar 2012, 22:23)

Ok I am new at this so forgive me, Am I right in saying that you have there a USB to TTL "converter"? if not what is it? smile

And does this device (I guess it does) show up as a COM port on your machine to allow you to interface with UART capable hardware?

Thanks!

(Last edited by CreepyBloke on 22 Mar 2012, 00:25)

CreepyBloke wrote:

Ok I am new at this so forgive me, Am I right in saying that you have there a USB to TTL "converter"? if not what is it? smile

Yes, you are right smile

It has other signals that I haven’t gotten into yet.

CreepyBloke wrote:

And does this device (I guess it does) show up as a COM port on your machine to allow you to interface with UART capable hardware?

Yes. On my Linux laptop after plugging I immediately got a serial device ttyUSB0 and it was ready to go. On Windows I guess you have to install a driver, but you brought that nto yourself by using Windows. The TTL part is just the voltage downshift to 3.3 or 5 volts. It’s still straight serial.

CreepyBloke wrote:

Hi everyone,

I am trying to create a cable as above. I ordered a clone CA-42 from ebay and did some testing with a multimeter, I seemed to have 2 VCC's so I opened it up and to my surprise I found 2 wires soldered to a single point on the PCB, there are 4 wires total so I expected to find a VCC, GND, TX & RX.

wasn't easier to check the corrispondence between pins on the "phone" port, and wires??? without even touching the "usb side" of the cable?

http://buffalo.nas-central.org/index.ph … _Each_Wire

(Last edited by nebbia88 on 22 Mar 2012, 14:44)

Hi sorry I have been away for a few days, I did try that at first nebbia88 but like I said I found 2 of the wires were giving a reading of 3.3V and it confused me so I just opened it up to see what was what.

I now have my DKU-5 cable here and will post some pics tomorrow

Thanks

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