[DSP-10] U107 Voltages

[Yamamoto Jiro]

Hello Steve,

Thanks for the detailed description for your solution. I will try it 
when I get another 74HC14. BTW I am also interested in a "software fix" 
instead of a "hardware fix". The idea of the software fix is to modify 
the code in UHFA where a bit pattern is set for each of RF gain. For 
instance, What if '10001000' for RF gain 100 were replaced with 
'01000100'? I don't know if this works or not, but I am just curious.

Jiro JQ2LMG

On Sat, 6 Mar 2004 19:13:03 -0700, Steven Bible wrote:
> Hello Jiro,
> 
> The problem comes from the level shifters on the KDSP10 board (the
> PI5C3245S).  Level shifting takes time, and you see this in your o'scope
> traces as sloping traces on the Serial Clock (FL2) and Serial Data (FL0).
> 
> My solution was to use an additional 74HC14 DIP and piggy back it on top of
> U3 on the KDSP10 board.  Bend pins 1 through 6 and 8 through 13 pins
> straight out from the package.  Be careful not to stress the pin too much as
> you bend it, they may break.  Clip off the narrow part of the pin and leave
> the thick part of the pin.  Allow the power (pin 14) and ground (pin 7) pins
> to stay the same, hanging down.  Piggy back the 74HC14 to the top of U3 by
> soldering the power (pin 14) and ground (pin 7) pins to the same on U3.
> This provides power and groud to the top 74HC14.
> 
> Connect a wire from P2-4 (FL2) on the KDSP10 to pin 13 of the piggy back
> 74HC14.  Connect a wire from pin 12 to 11.  Connect a wire from pin 10 to
> the through hole capacitor for FL2.
> 
> Connect a wire from P2-3 (FL0) on the KDSP10 to pin 1 of the piggy back
> 74HC14.  Connect a wire from pin 2 to 3.  Connect a wire from pin 4 to the
> through hole capacitor for FL0.
> 
> I appoligize for only words to describe the above solution.  If you like, I
> can take some photos and post them to a web page.
> 
> Please let us know if this helps solve your problem.
> 
> 73,
> 
> - Steve, N7HPR
>  (n7hpr@tapr.org)