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Re: CW Offset does NOT work on Raduino_v1.14.1 for BITX40

 

Hmm, yes you may be right that in some cases the 7805 output hasn't
dropped sufficiently to represent a digital LOW.

Another way to circumvent this situation might be to define A0 as an
analog input and define a higher threshold for a digital LOW/HIGH. What do
you think?

73 Allard PE1NWL

On Wed, June 14, 2017 18:07, Jerry Gaffke via Groups.Io wrote:
The code is doing a digitalRead(PTT_SENSE), I'd expect the threshold on
the nano to be somewhere between 1 and 2 volts
The problem is that when the +12v TX line into the LM78L05 at U3 goes to
zero volts, the output of U3 remains up around 5v because there is no
place for the charge on C150 and C151 to go. ??The pulldown resistor will
eventually discharge those caps. ??The RC time constant of 0.2uF*20k = 4
milliseconds, which should be fast enough. ??I'd put that new 10k resistor
from U3-1 to ground, rather than from A0 to ground, the latter case would
reduce the maximum voltage into the Nano A0 pin down from 5v to 2.5v.
??This also reduces the RC time constant to 2 milliseconds.
??

On Wed, Jun 14, 2017 at 08:28 am, Jack Purdum wrote:


Given your code, Allard, I'm surprised he needs a dropping resistor on
that line.
??
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