[minima] Re: Minima - Essential Modifications Errata & Notes
- From: Thomas Sarlandie <thomas@xxxxxxxxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Sat, 18 Oct 2014 11:37:19 -0700
Steve,
Some answers below in the text and some additional suggestions.
>
> 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?
>
>
The only available software that supports it is Eldon firmware (as far as I
know). I am working on merging this into the mainstream firmware. The pin
he used is pin 7 (Also called BAND_LOW_PIN).
> > - Adding a LM7809 to get a stable 9v supply to the BFO.
>
> Will do. Zener do the same thing more cheaply?
>
>
Probably. Not as much familiar with Zener as I am with lm7809 though. Will
the power consumption impact be similar? Is the stability in time and
temperature sufficient?
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?
>
>
I am not a big fan of those keyboard and do not see myself adding one to
the front panel of my Minima but I second the fact that we should have this
as an available option and the stock firmware could support it.
> 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.
>
>
This is an interesting idea (reusing the PB pins). It does make the wiring
a bit more complicated for those of us doing it manually but in a world
where we have PCBs for the main board it sounds better than pulsing.
I guess the question is do we really need 16 filters? Who is going to build
that many filters in a Minima? If you want to go that far, why not just use
a i2c i/o expander? That is less wires to route to the LPF board.
> 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!!
>
>
I agree that finding a way to have pins available for that would be great
so that one schematic could support different input methods without
requiring too much rewiring or reprogramming.
More ideas for changes:
- Separate the serial port adapter. Most people will use a cheap
USB-serial adapter and many of those work in 5 volts. We do not need the
transition to 12v. We can keep the adapter parts (two transistors and a few
resistors I believe) as an optional block on the schematic.
- Add a 1uF capacitor between the DTR pin of the serial adapter and the
reset pin of the arduino. With this extra capacitor, the standard Arduino
environment is able to automatically reset the board and you do not have to
do "press reset a few seconds after clicking the programming button" trick
anymore. I think this is a must have for anyone trying to make changes to
the firmware. Otherwise Arduino will drive you crazy because you will not
press the button at the right time.
I would call this schematic Minima 1.1. Since we do not have a clear
decision on the mixer we could publish that now and then make a Minima 1.2.
I vote for Kicad to draw and distribute the schematic. It is open source
and most open projects have switched or are switching to this tool. I was
more familiar with eagle but I think it is time to follow the wind of
change. I believe someone already re-drew Minima 1.0 in Kicad. Correct?
73,
thomas
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