[minima] Re: Minima - Essential Modifications Errata & Notes
- From: "Steve VK2SJA" <vk2sja@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Sat, 18 Oct 2014 19:26:05 +1100
Hi Thomas/All,
> I would add:
>
> - Updating on the schematic the lines that control the LPF relays in the
> amplifier (Instead of the initial 3 we now use one for the LPF on the main
> board and one for the RF386 amplifier).
Will do. Question. What pin in on the AVR is being used for the RF386 band
select? I never saw anything documented on that one. Did I miss something?
> - Adding a LM7809 to get a stable 9v supply to the BFO.
Will do. Zener do the same thing more cheaply?
> And if you have the energy to start a list of optional changes, I would
> include:
> - 9 buttons by eldon
> - Rotary encoders by eldon
Can do.
While we're talking about "enhancements". I've got a couple of ideas to
throw out there for discussion (and this is not intended to be dismissive
of Eldon's most excellent coding efforts. Great work Eldon!).
But my musing goes something like this...
Rather than using ~6 resistors for ~6 buttons (yes I know I'm
approximating). Why wouldn't we cut to the chase and do this:-
http://playground.arduino.cc/Code/OneWireKeyPad
That's pretty much the same number of resistors but you get an entire 4x3
or 4x4 keypad. Still only uses one logic pin on the Arduino. The cheapest
pushbutton switches I can buy from the local electronics store are about
$1.50 each 7*1.50 = $10.50. Whereas a 4x3 keypad from the same place is
about $9 and a 4x4 keypad is $13.00. So the cost is about the same and I
don't know how others feel. But I think the keypad would be a lot easier
to mount neatly in a project than fussing with 6 or 7 individual
pushbuttons. And the keypad would open up a world of options for the
software. Direct entry of a frequency anyone?
Well that's one thought. What thinks 'ye all? Eldon, would this keypad
idea integrate with your software without major re-write?
That's idea number one.
Next idea. Band switching.
Why wouldn't we get a four bit latch chip. Something like a 74LS75. Cost
about $1.50 about the same as the CD4017. Daisy chain the LCD data lines
to the 4 bit latch (PB0, PB1, PB2 & PB3). Use pin 11 PD5 for the latch
enable. Now instead of using 2 AVR pins your only using one. You have a 4
bit binary code to use of band selection. So that's 16 bands. You still
use the MSB for the LPF selection. Similar to the encoding scheme Mark
originally proposed. Except now we have 4 bit encoding instead of three.
So we have 8 possible bands below 15Mhz and another 8 above.
Latched bits to my mind seem somehow more "bulletproof" than pulsing a
counter. And the transition from point A to point B is direct and only
involves switching the relays actually required.
But the best part if you do this. Is that then you can permanently assign
the two free pins PD7 and PD6 to a rotary encoder!!
Anyway. just a couple of thoughts to throw out for comment.
73, Steve.
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