[CART360] CART 360 _Arduino 'sample rate'

[Vincent Leclerc]

8-bit w/ r2r = 8 I/O pins from the arduino.

In the makezine example they use D0-D7.

Vincent

On Sat, Oct 17, 2009 at 12:03 PM, Morgan Sutherland
<morgan at morgansutherland.net> wrote:
> The R2-R ladder used 1 output from the Arduino. How does adding a bunch of
> resistors add sample resolution to a signal that was originally 1-bit?
> That's a rhetorical question – it can't – but perhaps it interpolates?
> Ah, the wikipedia article[1] leads me to believe that this is the case (as
> it describes the circuit as useful for D/A conversion).
> 1. http://en.wikipedia.org/wiki/Resistor_ladder
>
> On Sat, Oct 17, 2009 at 10:37 AM, Vincent Leclerc <v at uttermatter.com> wrote:
>>
>> Hi Jon,
>>
>> This is often confusing. There is a big difference in sample rate and
>> sample resolution. I added a graphic at the bottom of:
>> http://hybrid.concordia.ca/~cart360_vincent/studio/05/
>>
>> The 2 graphs show 2 completely different sound samples.
>>
>> The first graph shows a 1-bit resolution sound sample and the second
>> shows an 8-bit resolution sound sample. That is sample resolution.
>>
>> Now for sample rate -- the amount of samples you record (or generate)
>> per second -- you can see that at [a, b, c] we record samples at the
>> same time. In the 1-bit resolution sample, you always record 5V, but
>> for the 8-bit sample we record [2.5V, 1.88V, 1.25V]. This is why
>> sample resolution is as important as sample rate.
>>
>> Generally the Arduino outputs with a single digital pin, so it outputs
>> at a 1-bit resolution, regardless of your sample rate (which can be
>> quite surprisingly high as you said in class).
>>
>> If you want 8-bit resolution output, R-2R ladders are the
>> easiest/cheapest way to go about it.
>>
>> http://blog.makezine.com/archive/2008/05/makeit_protodac_shield_fo.html?CMP=OTC-0D6B48984890
>>
>> Hope it makes things clearer.
>>
>> Vincent
>>
>>
>> On Fri, Oct 16, 2009 at 10:33 PM, joN <jonnygexter at gmail.com> wrote:
>> > Hi.
>> >
>> > There's something confused in my understanding of sampling (or the
>> > opposite,
>> > reconstructing)..
>> >
>> > I was thinking about what you said in class when I mentioned the Arduino
>> > was
>> > shooting out samples at a rate equivalent to a CD player. Did you say
>> > that
>> > the resolution of the Arduino is be one BYTE or one BIT?
>> >
>> > Using digital out means the speaker is either HIGH or LOW, which would
>> > be
>> > equivalent of one BIT. But my guess is that the voltage being either
>> > high or
>> > low relates to amplitude.
>> >
>> > On the other hand, if you said one BYTE, I would think you meant the
>> > integer
>> > stored as the timeHigh value (time period to switch the speaker
>> > HIGH/LOW),
>> > (though the Arduino reference says that ints are stored as 2 bytes). If
>> > this
>> > is what you were referring to, then my thinking is that this value
>> > relates
>> > to the possible quantized units, as in discrete, non-analog values, I
>> > can
>> > use to set the frequency.
>>
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>
>



-- 
Vincent Leclerc

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