Cm-108 counterfit?

I ordered a cm-108 fob from china, and this is

what I got.
is this a counterfit?
if not what are the pins i need for the ptt and cos ?

Hi Mike,

What markings are on the chip if any? The image you’ve included is very small.

It could be a CM108 chip in a different package, although I’ve never seen a CM108 in a SOP form. I note the board marking is mini CM108.

From a quick search I can’t find a datasheet that shows a pinout for that “CM108” variant.

I recommend purchasing a CM108 board (not the mini CM108).

the only markings are cm108 on the chip.
I ordered the board i always order, but got this piece of…
I am very low on funds so, returning is out of the question. and ordering another may be 10 bux, but its 10 bux I don’t have.
I haven’t been able to find a datasheet on this chip form either.

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It requires some ckt modifications (tricky, requiring a steady hand). I’ll look for my documentation tomorrow on how I modified these unites in the past (cut out a pwb trace and add a wire).


have you modified this particular chip form?


Sorry I shouldn’t have assumed you’d be in a position to order another fob. I look forward to seeing Bob’s modifications.

upon further work, I’ve found that the hamvoip software won’t even recognize that fob.
apparently it isn’t even a cm108.
so My next recourse is to see what ebay can do for getting me a rebate

I have been soldering a # 30 wire to pin 13 - goes to +3.1 for PTT → I add a 4.7K resistor to the base of a 2n2222 (grounded emitter) and use the collector for PTT - Let the DSP handle the Squelch and COS / Tone Decode - so only 4 wires - GND, PTT and RX and TX audio - I remove the 3.5 MM Jacks with hot air and add a 56K or 470K resistor (some need more receive signal) and 4.7K in the spkr out (transmit) line - these on ebay worked OK for me - 10PCS CM108 USB Drive Free Sound Card Laptop Computer External Sound Card Module | eBay steve nu5d

First, I have several variations of this USB device; same CM108 with different layouts. I’m sure they are all made in China. I found I had to reverse engineer each configuration. PTT requires an added open collector circuit. As I said before, soldering is tricky to get a good joint without inserting unwanted solder bridges. It took my old hand/brain coordination a few tries to get the soldering tasks down.

Enclosed are links to work from others.

I was not able to locate my data


The fob I got was definitely counterfeit, It wasn’t even a cm-108
so If anyone gets a fob claiming to be a cm-108 and the chip is a 24 pin dip, you’ve been had.

The pic you posted wasn’t a DIP package. It’s an SOP

Sorry, my terminology is a bit rusty