10 DACs - 1 Arduino

Does anyone know of a simple way to control 10 DACs with a single arduino?
I am using a DUE right now which has 2 DACs built in so I need another 8...
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I bought the sparkfun/ Adafruit DAC breakout boards but they only have two addresses for I2C so I can only use two at a time with one arduino/I2C.... that only gives me 4 out of 10 :frowning:

I thought of maybe wiring some arduino Pro Mini's to sets of two DAC's so that a digital out from the DUE tells the individual (1 1ProMini/ 2 DAC) groups what to do... but that requires a DUE and 3 more arduinos...

Anyone know of a simpler way to get 10 DAC outputs (10 bit minimum)????

Maxim makes several 8 channel DAC's with SPI interface.
http://para.maximintegrated.com/search.mvp?fam=precision-dac&527=12&tree=daconverters
is the parametric search page. Narrow from there.

The Due has 12 analog inputs. Or more correctly, a 12 channel analog switch to an ADC.

Do you mean that you need 10 separate ADCs? Can they not be switched, or do they all need to be synchronized for some reason?

I actually need 10 DACs not 10 ADCs...
I need 10 true analog outputs from the arduino with at least 10bit resolution each.

Could I maybe do some kind of switching or multiplexing with the I2C to control the 10 dac boards???

This is what I bought only because it has an existing library, but did not realize it can only be set to one of two I2C addresses:(
its a bit misleading because the chip spec sheet claims it can do 8 addresses, but further reading shows only two can be accessed by the user and any 2 of 8 can be preprogrammed onto the chip during manufacturing per user specifications

I tried controlling the device using the PWM (fake analog Outputs) but the radio I'm controlling did not like that....
I am basically bypassing a manually operated potentiometer and controlling it via arduino so I am removing the pot and feedint the connections an analog 0-3.3v signal instead....( 10 times...)

fxmech:
I tried controlling the device using the PWM (fake analog Outputs) but the radio I'm controlling did not like that....

PWM without a RC filter won't give you an analog voltage.

Doh! Sydlexia ksirtes agian.

I see the Adafruit page says:

We break out the ADDR pin so you can connect two of these DACs on one I2C bus, just tie the ADDR pin of one high to keep it from conflicting.

When you tried using the PWM "analog" outputs, how did you filter it?

Have you considered using SPI devices? It'll take more pins, but it seems like it may be simpler. And if you are replacing potentiometers, would digital pots be a better choice? Depends on the resolution you need.

What is the sampling rate or highest frequency DAC should outputs?
You may be need De-Mux, the same way as 1 ADC is able to read 12 inputs, 1 DAC can be DeMultiplexed to 8 or even 16 outputs. SFE has a board with 74HC4067, AFAIK.

When I tried PWM I did filter it with a capacitor and resistor combo but It was either choppy or when a bigger capacitor was used it got less choppy but slower and just wasn't a doable scenario. I am interfacing into a pot on a radio that runs on 12 bit resolution.

The adafruit breakout buards can be set to any one of two prewired channels so I2C is not a good option because it can only talk to two DACs at a time

Havent seen any SPI DACs... my problem is that I am not super savy with these things so working with a plain DAC chip with no library might end up outside my limits.

Just looked at the SPI link.... that might be the ticket!!!

The problem is that most DACs are single or dual channel only. There are some quads but
they seem to all be surface mount QFN style packages. 4 SPI dual dacs would need 6 or
7 pins to drive. (such as MCP4912)

Multiplexing output from a DAC still requires some sort of sample and hold on each channel,
which might just be a capacitor if theres only a high impedance load to drive, or capacitor
plus opamp if not.

So SPI DAC, 1->8 analog multiplexer, 8 capacitors and two quad opamp packages perhaps?
You'd have to refresh the capacitors regularly depending on the input current of the opamps
and the quality of the caps (note: not ceramic or electrolytic for this application, stable
plastic film are needed for 10 bit accuracy)

Alternatively connect 8 parallel-input 10 or 12-bit DACs to the same databus, drive it
from a pair of '595 shift registers, use another shift register to control the DAC strobes?

Or be luckier searching for the right chip. 8 bit DACs are much more plentiful

A TLC5940 with filter capacitor on each output...?

I think we need more specification. What's it connected to? What's the bandwidth? etc.

Using an Op Amp lowpass filter or even a two stage passive low pass is much better than a single RC lowpass.

I am basically bypassing a manually operated potentiometer and controlling it via arduino so I am removing the pot and feedint the connections an analog 0-3.3v signal instead....( 10 times...)

Ar they all 10k pots? ive had some luck with digital potentiometer and an arduino

Yes 10k pots!
I've never worked with digital pots...
Do they work like regular pots with an additional digital input?
If you have any part suggestions let me know...
Trying to stay away from surface mounts for the prototype build

Thanks for all the help

fxmech:
Do they work like regular pots with an additional digital input?

Well yes and no. The voltages present must always be within the supply range,
the device is simply a switched resistor network using CMOS transmission gates
to do the switching, so its like a pot with detents, quite a lot of detents.

Sparkfun.com sell a digital potentiometer break out board that i have had success with. There is even a tutorial floating around on Google.