microchip ADC - DAC

[Dimitree]

hi everyone
I was wondering if microchip make some good ADC or DAC, so I searched on their website and noticed that the only ADC with a high sample rate is the MCP3901. it says: Max Sample Rate (samples/sec) 64000. this means that it can be used to sample an analog signal at 44.1khz? it's a 16bit ADC.
for the DAC, the max value is 12bit. now since I'm not an expert of those things, how can I understand if those DAC could be used for audio? (I don't mind for the 12bit, it's just for fun)
many thanks everyone!

[zeptin]

I'm finding it a bit hard to interpret the datasheet for the MCP3901, but from what I can see it isn't suitable for good quality audio. Judging from some of the performance graphs it isn't intended to be able to handle the full audio range (i.e. up to 20kHz) and I see the figure of 15ksps popping up a lot. If you want my opinion, go for a codec chip like the ones made by Analog Devices: http://www.analog.com/en/audiovideo-products/audio-codecs/products/index.html

Those are designed for audio and are easily capable of 16 or 24 bit operation. They also have the ADC and DAC in one chip, which makes it a bit easier to work with them. The only downside is that they're all almost certainly surface mount packages, which may make them unsuitable for what you want to use them for.

Another option is using one of the dsPIC microcontrollers from Microchip, there are a few models that have 16 bit DACs for you to use, along with 12 bit ADCs, and they're reasonably powerful devices for basic DSP or audio work. The two devices I know have DACs are the dsPIC33FJ128GP802 and the dsPIC33FJ128GP804. You might be able to get these in a DIP package, which will be a lot easier to work with than a surface mount codec.

Hope this helps a bit :-)

[Dimitree]

thanks it helped!
I have a dsPIC here, the GP804 you mentioned, but my programmer is old so I never used this pic. about the microchip DAC and ADC I wanted to try those just to start, since are cheap and easy to find. which one on the AnalogDecive page you recommend to start with? I don't need perfect audio quality, I just want a sound out of the PIC 

[zeptin]

Well, just about any of those codecs would work, but they might be complicated to work with. If you just want to be able to hear sound from the chip, have you considered using the 12 bit ADC that just about every Microchip processor has built in, and then just use a PWM pin with an external low pass filter to generate the sound? It won't sound amazing, but it's not very difficult to get it to work.

Alternatively, it looks like this guy is on the right track to getting something working, and he's using Microchip ADCs and DACs: http://www.diystompboxes.com/smfforum/index.php?topic=88921.0. I can't guarantee his circuit layout is perfect, but it might be useful to see how he's done it.

[Dimitree]

ok I could try one of these by Analog Devices, but, in the product description there's a lot of infos,
could you help me understand which kind of converter could be more suitable for me, to use it with a pic (obviously not for DSP operations with a PIC, just for interfacing) ?

[cctsim]

You could try this dev kit for speech and audio:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en534506

It is also relatively cheap and has a mono codec integrated on top of the dspic ADC/DAC capabilities.

[Dimitree]

You could try this dev kit for speech and audio:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en534506

It is also relatively cheap and has a mono codec integrated on top of the dspic ADC/DAC capabilities.

many thanks for the suggestion, but my aim is more about understanding how to combine the different devices togheter rather than using a dev kit to start learning the DSP programming, so first I'd like to choose the single components and use them (even with bad results)

[cloudscapes]

maybe a dedacated codec chip?

I bought a few pcm3500's the other month. though I haven't actually seriously looked at them yet, according to the datasheet, you can simultaneously send to its DAC and recieve from it's ADC in far less time/clock cycles than communicating with seperate ICs would take.