[App_rpt-users] USB FOB pin 13 (PTT)

[Andrew Errington]

> First ... I'll comment on the USB unit.... The chip within is covered by
> a blob but it detects as a CM-109 and appears to function properly as far
> as audio and COS ... only the PTT logic has failed to output during my
> limited testing.

If the chip is epoxy-blobbed, how can you connect to pin 13?  GPIO is not
required for basic sound-card functionality, so it's often not bonded out
from the die.  It's quite possible that you simply can not access GPIO. 
Of course, since I haven't seen your device it's quite possible that you
can access it after all.

Another possibility is that the GPIO you can access is not actually GPIO3,
the one that is usually bonded to pin 13.  You can get the CM109 datasheet
on-line and you can see there are 8 GPIO pads on the die.  If a different
GPIO is bonded out then could you change the app_rpt configuration to
drive a different bit number?


> My assumption about the actual sequence within the chip process was in
> line with your great explanation. What I lacked is understanding if there
> is a way to force the software into a transmit mode for testing purposes.
> Doing so, as you explain should activate the PTT logic.

Well, I don't use app_rpt, but maybe there is a test function you can use.
 It would be quite handy for debugging.


> Your info about Thomas Sailer's soundmodem is something I am very
> interested in. I had another project in mind and decided to venture into
> Asterisk and App-rpt in order to to utilize USB sound modules.
>
>
> Your information may very well be a solution to another problem I would
> like to tackle. I will definitely have a look.
>

Feel free to email me on- or off-list.  I'm no expert, but I have dabbled
a lot, and I have absorbed a lot of the information that others have
written on this topic.

Sadly the CM108 packaged parts are becoming scarce as manufacturers move
to the cheaper epoxy-blob process.

73,

Andrew
ZL3AME