microcontroller for simple audio project
in [Embedded]
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From: ethan on 2 Feb 2005 15:38 i'm looking more for audio generation as opposed to audio decompression, so the AT89C51SND2 is probably out. do you know of an app note that explains how to use PWM to generate audio output? the atmel AVRs are appealing for a number of reasons, i guess i need to figure out if the DAC is a requirement or not...
From: Mark Borgerson on 2 Feb 2005 16:09 In article <1107376351.002612.227710(a)c13g2000cwb.googlegroups.com>, ethan.bordeaux(a)gmail.com says... > i've thought about this, but am concerned about MIPS and power > consumption. any idea on the processor overhead to implement this? is > this something that could be implemented with PWM or a typical uC timer > allowing for very low overhead? i want as many cycles as possible to > calculate new outputs, so i'd rather not be stuck shifting bits. an > onboard parallel DAC seems like the easy choice, but since i'm trying > to be very cheap, i might not have the luxury of going the easy route! > > Yes, this chore is something that many MCUs with a hardware PWM capability could handle. Changing the output voltage then becomes a matter of storing the new value in a register. The output sample rate is then limited by the timer clock rate and the number of bits resolution. For a timer with an 8MHz clock and 8 bits output resolution, the PWM period is 256 cycles, or about 31,250 steps per second. That, and the acceptable distortion, will limit your maximum output frequency. If you only need 5KHz output response, you could use a slower clock speed or more bits of resolution. The PWM generation will probably not be the limiting factor in determining your maximum frequency. It will take only a microsecond or two to adjust the output. You still have to calculate the next output before the next output sampling point. Mark Borgerson
From: Anthony Marchini on 2 Feb 2005 17:20 ethan wrote: > hi, i'm looking for a uC for a simple portable audio project. the > basic specifications i'm looking for are: > > - 8/16 bit datapath > - hardware multiply (8x8 ok, more bits the merrier) > - 20+ MHZ instruction execution > - onboard flash/SRAM (8kbytes+ FLASH, 1kbyte+ SRAM) > - UART > - onboard DAC (mono ok, stereo better) > - free build tools > - cheap! > > right now i'm looking at the SI Labs C8051F330. it's right at the low > end of most of my criteria, but it's the only inexpensive uC ($4.27 > quantity 100) i've seen with an onboard DAC. does anyone out there > have experience with this part? also, is there something else i should > be looking at? SI Labs have some larger FLASH variants (for example > the C8051F017) but they sell for $12 in similar quantities, so that's > out. the atmel AVRs are appealing for a number of reasons, but they > don't have a DAC. anyone aware of a cheaper option than the C8051F330 > for a full uC/flash/DAC system? is there a good very cheap DAC one > could easily interface with an AVR? > > i'd love to use a DSP, but i believe they're just too pricy and don't > come with the level of integration i need. feel free to prove me wrong > on this assumption. > > thanks a lot for the help! > > ethan > Well, I don't know what your idea of cheap is, but you could look at the Cirrus Logic EP9302, you need a lot of extra components, but these things were designed for media output I believe. Experimental boards from www.embeddedarm.com and other people are available. This one in particular has a math coprocessor. It really depends on where you want to expand to. Tony
From: Anthony Marchini on 2 Feb 2005 17:25 Anthony Marchini wrote: > ethan wrote: > >> hi, i'm looking for a uC for a simple portable audio project. the >> basic specifications i'm looking for are: >> >> - 8/16 bit datapath >> - hardware multiply (8x8 ok, more bits the merrier) >> - 20+ MHZ instruction execution >> - onboard flash/SRAM (8kbytes+ FLASH, 1kbyte+ SRAM) >> - UART >> - onboard DAC (mono ok, stereo better) >> - free build tools >> - cheap! >> >> right now i'm looking at the SI Labs C8051F330. it's right at the low >> end of most of my criteria, but it's the only inexpensive uC ($4.27 >> quantity 100) i've seen with an onboard DAC. does anyone out there >> have experience with this part? also, is there something else i should >> be looking at? SI Labs have some larger FLASH variants (for example >> the C8051F017) but they sell for $12 in similar quantities, so that's >> out. the atmel AVRs are appealing for a number of reasons, but they >> don't have a DAC. anyone aware of a cheaper option than the C8051F330 >> for a full uC/flash/DAC system? is there a good very cheap DAC one >> could easily interface with an AVR? >> >> i'd love to use a DSP, but i believe they're just too pricy and don't >> come with the level of integration i need. feel free to prove me wrong >> on this assumption. >> >> thanks a lot for the help! >> >> ethan >> > Well, I don't know what your idea of cheap is, but you could look at the > Cirrus Logic EP9302, you need a lot of extra components, but these > things were designed for media output I believe. > Experimental boards from www.embeddedarm.com and other people are > available. > This one in particular has a math coprocessor. > It really depends on where you want to expand to. > Tony > I think I reversed the spec, this thing has AtoD not Dto A. Its a big chip, my guess is you don't want to bother with an operating system either. Tony
From: Jim Granville on 2 Feb 2005 18:58
ethan wrote: > sure no problem. basically i'm looking to create an extremely simple > autonomous synthesizer. waveforms would be generated through wavetable > synthesis (with linear interpolation if i can afford it) and others > through simple bitshifting algorithms and reading noise buffers. there > will also be some simple FX (FIR filters and other more novel but cheap > functions), envelopes, and a basic sequencer. as for sampling rate, > it's TBD. i just need to be able to generate enough channels of audio > to make something interesting, then i'll set the sample rate as high as > my MIPS with allow. no MIDI, at most some rudimentary interaction via > knobs or pushbuttons. i've implemented all of this on a DSP (see > www.dspmusic.org or www.dsperado.com/chiclet for some info), but the > total manufacturing cost is going to be too high, so i need to move to > a uC. i know i can make reasonably good music with a 33MHz ADSP-2181; > i'm hoping that if i cut some corners i can make something passable > with a 20MHz 8052. ideally the processor would have a DAC and flash > onchip for lower system cost. the DAC is proving to be the tough > request; only a couple manufacturers include them in low cost > processors. once i start looking at things like a standard product > ARM7 the price difference between them and a DSP is pretty small, so > there's little advantage to port. however getting a whole system on > chip (like the C8051F330) for ~$4 is quite enticing. Then start with the F330, and get it operating. If you have some time headroom, but need more flash, the ADI family has obvious appeal to you... If when you are finished, you find more speed would help, look at the upcomming C8051F410. 66MHz core, Dual 12 bit DACs, up to 32K Flash, wide Vcc http://www.eltis.kiev.ua/pdf/C8051F410_short.pdf Perhaps include a SO8 SPI memory option, as the newest ones can read continually up to 50MHz, and give some MBytes of storage. -jg |