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[on:]

I was wondering if there was an arduino DAC library upcoming, that is under development?

[Reply #1 on:]

There is an Arduino DAC library under the Audio folder, its used by the Audio library.

..\Hardware\Arduino\SAM\Libraries\Audio\Dac.h

The library is geared towards buffered output, i.e. audio playback from a buffer using an interrupt to push new values from the buffer at a regular interval.

For direct access to the DAC use analogWrite(DAC0,ulValue); this will give you an output range of 0-255.

In the quick and dirty synth I have used analogWrite to set up the DAC, but then use

dacc_write_conversion_data(DACC_INTERFACE, ulOutput);

To write the output directly using 12 bit resolution rather than the 8 bit resolution provided by analogWrite

Duane B

rcarduino.blogspot.com

[Reply #2 on:]

Guys thanks for the help, I was wondering if there was an easy way to produce sine waves,triangle waves, etc.

[Reply #3 on:]

No, there is not, you have to use Direct Digital Synthesis to generate them, this project generates two ramp waveforms using DDS -

http://rcarduino.blogspot.com/2012/11/quick-and-dirty-synth-for-arduino-due.html

Out of interest, what do you want the waveforms for ? Generating them at 44.1Khz takes quite a lot of the processor time, generating them at 8Khz gives a much lower quality but takes very little processor time.

Duane B

rcarduino.blogspot.com

[Reply #4 on:]

Here you go, total overkill - a post on Arduino Due DDS including a sample sketch for a sinewave with frequency controlled by a pot on analog pin 0.

http://rcarduino.blogspot.com/2012/12/arduino-due-dds-part-1-sinewaves-and.html

Duane B

rcarduino.blogspot.com

[Reply #5 on:]

Looking at the assembly, the ISR is around 30 instructions, so accounting for some over head outside the ISR, generating a sinewave at a 44.1Khz sample rate is using around 2% of the Arduino Due processing time. Its huge improvement over the UNO which would really struggle with 44.1Khz. A lot of the improvement is due to the Due being able to operate on 32 bits at a time, the UNO needs 4 cycles to process 32 bits. Add the faster processor clock and the Due is cruising.

Not much happening here -

Code:

00080198 <TC4_Handler>:
   80198: 2101      movs r1, #1
   8019a: b510      push {r4, lr}
   8019c: 480c      ldr r0, [pc, #48] ; (801d0 <TC4_Handler+0x38>)
   8019e: f000 f9a3 bl 804e8 <TC_GetStatus>
   801a2: 4b0c      ldr r3, [pc, #48] ; (801d4 <TC4_Handler+0x3c>)
   801a4: 6819      ldr r1, [r3, #0]
   801a6: 4b0c      ldr r3, [pc, #48] ; (801d8 <TC4_Handler+0x40>)
   801a8: 681a      ldr r2, [r3, #0]
   801aa: 188a      adds r2, r1, r2
   801ac: f1b2 5f16 cmp.w r2, #629145600 ; 0x25800000
   801b0: 601a      str r2, [r3, #0]
   801b2: d901      bls.n 801b8 <TC4_Handler+0x20>
   801b4: 2200      movs r2, #0
   801b6: 601a      str r2, [r3, #0]
   801b8: 4b07      ldr r3, [pc, #28] ; (801d8 <TC4_Handler+0x40>)
   801ba: 4808      ldr r0, [pc, #32] ; (801dc <TC4_Handler+0x44>)
   801bc: 681a      ldr r2, [r3, #0]
   801be: 4b08      ldr r3, [pc, #32] ; (801e0 <TC4_Handler+0x48>)
   801c0: 0d12      lsrs r2, r2, #20
   801c2: f833 1012 ldrh.w r1, [r3, r2, lsl #1]
   801c6: e8bd 4010 ldmia.w sp!, {r4, lr}
   801ca: f000 b9e6 b.w 8059a <dacc_write_conversion_data>
   801ce: bf00      nop
   801d0: 40084000 .word 0x40084000
   801d4: 20070564 .word 0x20070564
   801d8: 20070568 .word 0x20070568
   801dc: 400c8000 .word 0x400c8000
   801e0: 2007076c .word 0x2007076c

Assembly generated using -
http://rcarduino.blogspot.com/2012/09/how-to-view-arduino-assembly.html

Duane B