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19 octombrie 2012

Another USB Interface

As some of you may already know, I made a complex USB interface with soundcard, CAT (Computer Aided Tuning)  COM Port, another COM Port for PTT and Carrier Detect and a 4 Gb flash memory.
It works very well on my home radio station but is not worth to carry it when portable.
I like to go portable and from time to time I miss digimodes when working with only 5 or 10 watts from my old and trusty Icom IC703.
I made a smaller box with the same configuration (not with flash memory) but even that is too large to carry on the backpack. No, I don't have the pictures yet...
So, it was time to made another one, even smaller and suitable for a pocket.
I already had some of the needed parts. It was here a small USB 2.0 hub, a USB sound card and some USB to COM adapters.
You already know the principle schematics so I don't bother to explain it.

 Here is the "box", finished.





It is barely larger than a small cigarette box! I choose to have the USB cable pigtailed.
On the transceiver side, I used the same DB9 COM connector like all my other interfaces.
Therefore, I can use the same cables that I already made because I hate doing cables!
The LED's are for:
Rx Squelch open, POWER, Transmit (PTT)
I "reused" a case from another project so , the first two LED's was already there. It was a PIC programmer.

You can click on the pictures for higher resolution.


What's inside?




In the left, it's the USB soundcard. I removed the jack connectors.
In the middle is the USB<>COM adapter. I was afraid that this one cannot work with CD and CTR but I selected in the properties "hardware flow control" and seemed to be OK.
For testing I used WINDMILL's COM Debug software. I could see how CD worked.

In the right, is the USB 2.0 4 port hub. I wired the LED for Power indicator.
In the upper side, is a custom PCB test board which have the audio level divider and two optocouplers for PTT and Squelch detect.
Why I put here a Squelch detect? Well, this interace may be used also for Echolink or for some repeater software so, a detection of carrier is essential! And why not to have this if it is so simple?


More details


 You can see here the two potentiometers. The one for Rx audio is 100 KOhm and the one for Tx is 1 KOhm.
It was necessary to put a 1,5 KOhm onto the microphone input of the USB soundcard. It seems that the integrated circuit detects the presence of the microphone!

On the other side there are some SMD resistors which protects the optocouplers from high currents.




 Another detalied view....


So, this is it! This is the third and, I believe, the last USB interface!
I do not put a CAT COM Port on this because I wanted to keept it smallest possible and with only necessary wires.

I will make the first QSO's right now!

73 de Adrian, yo3hjv

PS
I made this in around 90 minutes!
Of course, it was a trick! I was searching for the USB<> COM adapter's driver for more than 2 hours!
It is a CH340, the cheapest f^%$$%# adapter on market!

PPS
The forst contact is with Peter, PE1CDE!

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