microcontroller for simple audio project

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

Reply to
ethan
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I use some of the higher end SI-Labs parts and am relatively happy with them. One thing to watch out for: The 'free' compiler that comes with the development kit is only good up to 4K of code. The uncrippled version is over a KBuck.

Bob

Reply to
Bob Stephens

Theres a huge choice out there. What resolution DAC were you looking for? 16 bit audio grade might be pushing it a bit!

TI have their MSC series, 33MHz 32KB Flash, 1.2KB RAM. Not sure what their dev tools are like though, and I think the DACs are only 8 bit.

What about Analog Devices ADUC841? 20MIPS 62KB Flash, 2304bytes RAM, built in 12 bit ADCs and DACs $6:56

I'm not sure that an 8052-based system will have enough power for an audio app, so something like the the Analog Devices ADUC702x ARM based chips might be better: 45MIPS 62KB Flash 8KB RAM, 32 bit Multiply (also has 12 bit ADCs and DACs).

They seem to be having production problems with this family though, as it was announced in August but production quantities aren't yet available.

Continuing on up the ARM scale, Atmel have a wide choice of devices, most of which have more horsepower and memory than you specify. Not many have a ADC/DAC built in, but there is a huge range of converters out there to choose from.

Mike

Reply to
MSC

thanks for the warning and the info. if i choose an 8051 i'll probably use SDCC (or another free compiler, any advice?) for development purposes.

Reply to
ethan

thanks for the reply!

DAC resolution: basically just something that matches the native datatype of the processor. since i'm pretty sure i'll be using an 8 bitter, 8+ bits of precision should be fine.

TI MSC: hmmm, this might be worth looking into. the MSC1202Y3 is pretty similar to the SI Labs part i'm considering. that said, i'd rather not pick a TI part since i work for analog devices. ;)

ADUC841: speaking of analog devices, that one looks pretty good. lots of memory for the price. if 8k FLASH won't cut it, this looks like a viable option.

ADUC702x: those look great, but i bet the price is going to be too high. plus there's that whole not existing thing to contend with.

atmel ARM7 uC: i like these, but i think they were going to be too pricy. plus there's no integrated DAC and i'm trying to keep this as simple as possible.

as for whether an 8052 will have the power for an audio app, i suppose that really remains to be seen. i have some synthesis code written for an ADSP-218x DSP, need to try porting a bit of it to find out just much i'll be able to get done.

Reply to
ethan

I think more useful information could be given if you said what this 'simple audio project' was. What exactly does your micro need to do with audio?

ttyl,

--buddy

Reply to
Buddy Smith

This message is intended to be my own personal view and it may or may not be shared by my employer Atmel Nordic AB "ethan" skrev i meddelandet news: snipped-for-privacy@o13g2000cwo.googlegroups.com...

May not meet you price tharget but the AT89C51SND2 has both MP3 player decompression and a DAC. If you store lots of audio, then the compression may allow you to save on memory.

You can use rsiastors or PWM to generate a DAC. The new AT90PWM parts (which are hard to get) have

12 bit Resolution enhanced PWM from a 64 MHz input source which could be useful to generate a DAC. The high frequency allows you to use small components..

The 5V ATmega88 should meet your requirements if you use an 8 bit port and an external resistor ladder.

-- Best Regards, Ulf Samuelsson snipped-for-privacy@a-t-m-e-l.com

Reply to
Ulf Samuelsson

For audio outputs why not do it the way a cd does with a single digital output through a low pass filter. This is the same as the sigma part of a sigma delta codec. You can get a surprising amount of resolution with just a single resistor and capacitor.

The code to drive such a D/A is a few lines of C

w..

ethan wrote:

Reply to
Walter Banks

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

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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.

Reply to
ethan

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!

Reply to
ethan

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...

Reply to
ethan

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

Reply to
Mark Borgerson

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

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and other people are available. This one in particular has a math coprocessor. It really depends on where you want to expand to. Tony

Reply to
Anthony Marchini

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

Reply to
Anthony Marchini

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

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Perhaps include a SO8 SPI memory option, as the newest ones can read continually up to 50MHz, and give some MBytes of storage.

-jg

Reply to
Jim Granville

Just in case you aren't aware, Circuit Cellar issue 174 has an article on using the 1MIP ADuC812 as a digital filter. Unfortunately their single channel FIR/IIR filter has a Nyquist limit of 250Hz. The slow multiply instruction seems to cripple it somewhat.

Mike

Reply to
MSC

time

you...

read

wow the 410 looks great! too bad it doesn't seem to exist quite yet. any idea when this will be in production? the advance datasheet is dated almost a year ago (assuming they use DD/MM/YYYY nomenclature) - not that that really means anything in the world of microprocessor design!

Reply to
ethan

Somewhere ( Fujitsu ? ) was application note about using 2 PWM channels to get 16 bit resolution, "extra" hardware has 2 resistors, R for high byte pwm channel and 256*R for low byte.

r.

Reply to
Raivo Leini

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