David,
I did not have my brain fully in gear on this situation before. The
GPIO input is just that - an input to a 3 volt logic device with only a
500 ohm series resistor. So there is nothing to make it either a high
nor a low level. In the digital world it is known as a 'floating input'
and without some other (external) hardware addition, it may appear to be
either at a high or a low level depending on the "shifting of the winds
in the desert"
Sooo - that may be a normal response when a LO function is used on the
GPIO input signal.
Take note of the part in the menu instructions saying that some external
interface circuitry may be required.
The GPIO input has no pullup resistor to 3 volts to keep it high - that
means the voltage just floats at whatever it happens to be. If that
voltage happens to be below the logic threshold for a LO level, the
function will become active when that menu option is selected - and will
happen with nothing connected to the GPIO input. (The same might happen
when HI is selected in the menu too).
The solution is to bring that input level to a high state with an
external pullup resistor. One end of the resistor goes to a voltage
source (ideally 3 volts, but up to 5.5 volts will be tolerated. The
other end of the resistor goes to the GPIO input (ACC2 connector tip) -
and oh yes, the negative of the source powering it would connect to the
connector shell. Two AA battery cells in series and a 33K resistor
should work nicely and the batteries should last a long time.
Then your PTT switch, footpedal, etc. would place a short between the
ACC2 connector tip and shell when it is active.
Note also that if you make the GPIO menu selections for either HI or LO,
that condition may become active any time the plug is removed from the
ACC2 jack. In other words, you must connect an external high or low
logic level before turning the KX3 on.
You may find it easier to build an adapter and use the microphone jack
PTT input which has an internal pullup resistor which assures a high
state when the PTT circuit is open or inactive.
73,
Don W3FPR
-----------------------------------------------------------
David,
Contact KX3support(at)elecraft.com to see if they can offer any
additional wisdom. If it has to go back to Elecraft for work, that
contact at support is the starting place to obtain an RSA.
73,
Don W3FPR
On 10/18/2014 10:53 AM, David - KI4UVC wrote:
Nothing is connected to ACC2 currently - I was mucking around with menu
settings.
I tried reverting back to MCU2.23 and am having the same issue - radio hangs
at any change in ACC2 settings.
I didn't have this issue until I did the Extended Temp Calibration routine.
Radio is in the low 6000 s/n range - has all internal options except for 2m.
Might have to send back to Elecraft for some brain surgery...
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