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Re: A Little Help Here?

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On 5/12/2015 10:48 AM, Tessa Bonting wrote:
> Op dinsdag 12 mei 2015 10:08:51 UTC+2 schreef Rod Pemberton:
>
>>
>>> Nevermind.  I spent a little more time on it and found there was some
>>> overlap of the different digits on the select lines.  So I ignore any
>>> digit selects that aren't one-hot and it is working fine now.
>>>
>>
>> So, the one-hot digit selects weren't actually one-hot, but two- or
>> three-hot ... ?
>>
>> Was the data being latched?  So, this was just some sampling jitter?
>>
>> You didn't post your Forth fix, so I'm left wondering if an adjustment
>> to 'delay' in newdigit@ would've fixed this issue or not.

The fix was to reject anything that wasn't a one-hot value.  The delay 
was only inserted to allow viewing of the debug data on the output 
without being overrun.  I don't have the old code, but here is the new 
code, actually *very* new.  I just rewrote some of it for simplification 
and I no longer have the code I tested last night.  So this is untested 
and may have Jeff Fox counting bugs (as in, "it proves you can't count").

: one-hot ( n1 -- n2 ) \ return value if exactly one bit set
   case
     1 of 1 endof
     2 of 2 endof
     4 of 3 endof
     0 ( default )
     endcase ;

: newdigit@ ( c1 -- c2 ) \ sync to new digit
   begin digits@ one-hot 2dup = over 0= or key? not and while
     drop delay repeat nip ;

This code should work fine without the delay.  If you would like I'll 
test it without the delay.


> When I was programming for digital readout systems, like AtoD converters,
> I allways used to swith the display of by writing a all segments off
> to the display post, change the digit number and afther a little delay
> the new digit segment info to the proper port.
> This just to get rid of aftherclow of the prefious to the next digit.
> Thats why there is a possibility to read a double change.
> Succes, Tessa

The LEDs are being driven by an MCU.  I expect they are changing the 
digit selects and the segment drives at the same time.  Still, that 
would be a very low likelyhood that my MCU would see them both set at 
the same time (a few nanoseconds every 5 milliseconds).  I think it is 
likely that there is some slowness to the voltage transitions.  The 
anodes are pulled up hard by the outputs and tristated for a low which 
means they are pulled down passively so the transitions are relatively 
slow.  Actually I have seen this on the scope and didn't give it much 
attention.  The only reason the undriven anodes pull down at all is the 
10 kohm voltage dividers I added for 5v > 3v on the MCU inputs.

-- 

Rick

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A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 00:53 -0400
  Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 03:51 -0400
    Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 03:54 -0400
    Re: A Little Help Here? "Rod Pemberton" <bork@lllljunkqwer.cpm> - 2015-05-12 04:09 -0400
      Re: A Little Help Here? Tessa Bonting <tessa.bonting@gmail.com> - 2015-05-12 07:48 -0700
        Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 13:51 -0400
          Re: A Little Help Here? "Alex McDonald" <blog@rivadpm.com> - 2015-05-12 19:46 +0100
            Re: A Little Help Here? "Alex McDonald" <blog@rivadpm.com> - 2015-05-12 19:53 +0100
              Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 20:15 -0400
                Re: A Little Help Here? "Elizabeth D. Rather" <erather@forth.com> - 2015-05-12 19:29 -1000
            Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 21:18 -0400
  Re: A Little Help Here? all2001@spambog.com (Wolfgang Allinger) - 2015-05-12 08:37 -0300
    Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-12 20:18 -0400
      Re: A Little Help Here? all2001@spambog.com (Wolfgang Allinger) - 2015-05-12 23:08 -0300
        Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-13 03:31 -0400
          Re: A Little Help Here? all2001@spambog.com (Wolfgang Allinger) - 2015-05-13 07:32 -0300
            Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-13 16:47 -0400
              Re: A Little Help Here? all2001@spambog.com (Wolfgang Allinger) - 2015-05-13 17:48 -0300
                Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-13 22:01 -0400
  Re: A Little Help Here? Tessa Bonting <tessa.bonting@gmail.com> - 2015-05-13 08:56 -0700
  Re: A Little Help Here? Tessa Bonting <tessa.bonting@gmail.com> - 2015-05-13 09:22 -0700
    Re: A Little Help Here? rickman <gnuarm@gmail.com> - 2015-05-13 16:56 -0400

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