[Elecraft] ATTN LED low level activity

[Ron Hansen]

Hi Don, yes the rig is a K1, sorry I don't post much so I forgot.
Yes that has to be how the ATTN LED is getting pulsed. In my case
I am running the radio at 13.8 volt input so I wonder why all K1's
don't exhibit this issue... I will have to get my o'scope on it and look
a little deeper..
Being an old hardware guy I'm sure I can blame this on the software!!
Ron WA9ADT
--------------------------------------------
On Wed, 9/30/15, Don Wilhelm <w3fpr at embarqmail.com> wrote:

 Subject: Re: [Elecraft] ATTN LED low level activity
 To: "ron hansen" <ronadt123 at yahoo.com>, elecraft at mailman.qth.net
 Date: Wednesday, September 30, 2015, 7:39 AM
 
 Ron,
 
 That has to be a K1 that you are dealing with, although you
 did not 
 state it.
 When BAT is selected, the MCU samples the voltage produced
 by the R6 and 
 R7 voltage divider.  When ATTN is to be indicated, the
 MCU pulls pin 3 
 to a low state which turns on the LED.
 I suspect you are seeing the result of brief negative going
 pulses 
 between intervals when the voltage is sampled at the MCU pin
 3.
 I do not see any evidence of that behavior with a 13.8 volt
 power 
 source, but I suspect it may become evident with a low
 supply voltage.
 As you indicate, it should not be a big deal, but is only
 "interesting 
 behavior".
 
 73,
 Don W3FPR
 
 On 9/29/2015 11:20 PM, ron hansen wrote:
 > Just finished receiver portion of build on unit ser no
 3388. Everything
 > working so far but I discovered a strange condition
 with the ATTN LED.
 > Whenever the display is set for BAT voltage the ATTN
 LED very dimly flashes
 > at about 10 times per second. The flashing is sort of
 random and only
 > happens when BAT is selected. Seems like this control
 is coming from the
 > PIC, there is no other input to the LM358...
 > Not a big deal, otherwise the ATTN LED works fine..
 > Ron
 >
 >