[sdiy] sine wave floating point conversion issue

Dan Snazelle subjectivity at hotmail.com
Sat Feb 25 05:42:07 CET 2012

```Thanks everyone!!!

Sent from my iPhone

On Feb 24, 2012, at 10:29 PM, Veronica Merryfield <veronica at merryfield.ca> wrote:

> Divide is often expensive (although not always).
>
> unsigned char DacValue = (unsigned char)((sample*127.5)+127.5);
>
> On 2012-02-24, at 7:20 PM, Jay Schwichtenberg wrote:
>
>> Dan,
>>
>> Try:
>>    sine_int = (int) ((((sine_float + 1.0) * 256.0) - 1.0) / 2.0);
>>
>> Jay S.
>>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of dan snazelle
>> Sent: Sunday, December 31, 2000 4:52 PM
>> To: synthdiy diy
>> Subject: [sdiy] sine wave floating point conversion issue
>>
>> If I have a value in my program that is putting out floating point values
>> (to make a sine wave) between 0.0 and 1.0
>>
>> I would like to get these values into an integer value of between 0 and 255
>> for my dac routine.
>>
>> i tried changing the type and multiplying the value and then dividing it,
>> but then i ended up with negative and positive values....
>>
>>
>> here is the routine which MAKES the sine
>>
>>
>>
>> void loop () {
>> float sample;
>>  int j;
>>
>>    for(j = 0; j < NUM_SAMPLES; j++) {
>>
>>
>>
>>        sample = sin(2 * PI * FREQUENCY * j / SAMPLING_RATE);
>>
>>
>> sample is the value which is a float and puts out the number I want to
>> transform into something usable for the dacOutput function.
>>
>>
>> This has shown me I need to get better and basic type conversion, etc
>>
>>
>> thanks
>>
>>
>>
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>>
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>
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