[App_rpt-users] Quick sound fob question

Skyler Fennell electricity440 at gmail.com
Tue Oct 13 12:08:43 UTC 2015


Ok, I'll just solder the pin, just making sure. 

It's weird you can't switch the gpio pin for PTT in software.

> On Oct 12, 2015, at 11:54 PM, larry <larry at n7fm.com> wrote:
> 
> Skyler,   Short answer is No!
> 
> My experience with the sound fobs that look similar to yours , You will still need to solder to Pin 13 to get the PTT logic. No way around that as on the CM-108 chip Pin 13 is not connected to anything so no place else to get that logic other than soldering a wire to the pin.
> 
> As for the COS signal (CM-108 Pin 48) that can be gotten from the left side of the volume down switch SW1 if you want to avoid soldering the COS line to Pin 48 on the sound chip. CTCSS can be retrieved from the right side of volume up SW2
> 
> The Green LED is still the heartbeat indicator.  
> The Red Led on the Fob is NOT the same as the PTT LED indicated on the modification schematic.
> 
> In fact if you go here http://www.crompton.com/hamradio/usb_fob_modification/
> 
> You will find a good description of the connections on that particular fob.
> 
> Larry - N7FM
> 
> 
> 
>> On 10/12/2015 06:23 PM, Skyler Fennell wrote:
>> I previously got the CM108 sound fob from startech and had to solder to the tiny pin.
>> 
>> With this one 
>> 
>> http://ebay.com/itm/291156304476?_mwBanner=1&varId=590306532025
>> 
>> It looks like it already has both LED's installed. I am assuming the red led is the same as the transmit LED.
>> 
>> If this is so, does that mean I don't have to solder to the tiny pin on the CM108 and I can just drive a transistor with the same wire as the LED for PTT?
>> 
>> Skyler KD0WHB
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