I`m not Quite sure Where to start here, as some of you may already know from my last couple of blogs, I`v been working with the Duinomite board(s), and have one of these mounted on a breadboard (Kind of?), and of course this allows me to mess about quite nicely.
also some of you May remember that I have a Long-term project in mind involving A to D and D to A, and subsequent data manipulation (playing with Binary functions), to get something interesting out of it in way of Radio.
now DO NOT be put off by the word "Radio" this whole project is being kept as Generic as possible and open to Anyone, with reasonably easy to build kit! I have No desire to lose anyone, go over heads, or keep that Application specific that it would be useless to you unless you were me! 
here`s a pic of a Very simple D to A convertor, it uses a plain old R2R ladder network fired by a single 74245 buffer chip.
you Can use a 74244 if you want, but the 245 lends itself nicely in its pinout to through and though wiring, that`s the only reason I used it.
so yeah, here`s tho top from one angle:
and here`s another angle:
the cap nearest the IC is simple decoupling, the other is part of a Low-Pass filter for really High frequencies, as is the inductor at the rightmost side of the parts. the 330 Ohm resistor is simply for the LED, and Yes, some of you Old `uns will recognise that it`s a Very early LED when ther bases used to be metal (it was a nicer red too!), I just put that on there for old times sake as I love LEDs and the old ones take me back a bit 
for those that like Bottoms, I present This:
Yeah, No probably not at all what you thought it was going to be eh! 
so yeah, a bit of Arduino code to drive this sucker would be great, Right?
well I can`t do that I as it won1t let me cut/pste anything into here (unless it`s a website), but it IS being worked oh
here`s a pic of the D to A being driven by an Arduino Nano (a gift from Farnell):
now That (to me anyway) looks pretty darn Linear!
Not bad for £2 worth of 1% resistors, now I`m rubbish at maths, but I`ll try expalin My logic here, I went for 20K resistors and bought 200 of them (a penny each), I worked on a resolution 250 (yeah I know it`s 256 really) to keep the maths simple, so I got 250 into 20,000 made 80, So I needed a tollerance of 80 Ohms, 1% at 20K is 200 Ohms, so it was time to drag out the test meter and check each one and put them into piles according to their real values.
[a word to the wise, DO make sure you have a Fresh battery in your meter when testing!]
having done so, I soldered them in according to the R2R formula, and used still the same batch of 20k resistors in Parallel to make the R (mitigating by 50% any further error in values). hence the upright parts doubled up.
(you Could use 5% carbons too, but you would need to buy More and thus have more to test to get matching values)
so we have an Ardiono nano, making waves on a homemade D to A, but the titles Dev to Dev... Why?
well here`s the Full setup:
and NOW it all ties in Nicely, the Duinomite is actually working as the Oscilloscope for the D to A that`s driven by the Arduino.
Case solved Dr Watson!
oh yeah, I will post the code for each When I can figure out HOW
