Fyfkin
Posts: 3
Joined: Tue Jul 27, 2021 1:56 pm

Voltage analog output (non-audio DAC)

Tue Jul 27, 2021 5:17 pm

Hi Guys,

We are looking for Raspberry Pi compatible digital to analog converter capable of working with up to 100ksps speeds, minimum bit depth of 18bit and ideally 3-4 channels per board (or potential of multiple boards to be used with single computer at the same time). There are many such data output devices for Windows and there are plenty of audio converters for Raspberry. There are some industrial converters for Raspberry Pi that I found but generally they seem to be happy with 12bit resolution and not very fast.

Our target application is real time signal acquisition, processing and output, therefore to accurately re-build the signal into voltage we need to be able to accurately output voltage at high speed all within allowed time delay. We want to avoid designing custom board if possible.

If you seen any of such device please let us know!

aBUGSworstnightmare
Posts: 3492
Joined: Tue Jun 30, 2015 1:35 pm

Re: Voltage analog output (non-audio DAC)

Thu Jul 29, 2021 7:20 am

Searching mouser for 18-bit DAC https://eu.mouser.com/Semiconductors/Da ... ?P=1z0w2ww

Once pe-decided for a particular part check if there is a kernel driver for it, or what is your understanding of 'Raspberry Pi compatible'?

Fyfkin
Posts: 3
Joined: Tue Jul 27, 2021 1:56 pm

Re: Voltage analog output (non-audio DAC)

Thu Jul 29, 2021 7:41 am

aBUGSworstnightmare wrote:
Thu Jul 29, 2021 7:20 am
Searching mouser for 18-bit DAC https://eu.mouser.com/Semiconductors/Da ... ?P=1z0w2ww

Once pe-decided for a particular part check if there is a kernel driver for it, or what is your understanding of 'Raspberry Pi compatible'?
Of course, there will be many DACs available to buy as IC component that we could use to design our own board. And this is exactly what we are trying to avoid if someone already did this before. We are looking for solution that is already there as a form or HAT or standalone board communicating with Raspberry over SPI, I2C or USB. Raspberry Pi compatible in such case would be:
- Can be powered directly from Raspberry Pi
- There is a clear defined communication method/library available to send real time signal to the DAC at requested speed that was trialed/tested/used with this board so real time data output ability is proven on the platform
- Board already includes some form of output reconstruction filter & buffer amp (at least) for effective analog communication (not just DAC to generate voltage).

It is normally not an issue to receive or send single asynchronous messages over low level interface. But if you need real time communication it is different story as communication timing must be maintained.

It well may be there is no such solution available and we can accept that, however, it is always worth a try to ask.

aBUGSworstnightmare
Posts: 3492
Joined: Tue Jun 30, 2015 1:35 pm

Re: Voltage analog output (non-audio DAC)

Thu Jul 29, 2021 6:22 pm

If 2 channels are sufficient DAC8552, but 16-bit only https://www.robotshop.com/de/de/raspber ... gL0ffD_BwE

Everything else on google search for raspberry pi dac hat is audio. Don't think what you're up for is available as it is too niche.

Fyfkin
Posts: 3
Joined: Tue Jul 27, 2021 1:56 pm

Re: Voltage analog output (non-audio DAC)

Thu Jul 29, 2021 7:24 pm

aBUGSworstnightmare wrote:
Thu Jul 29, 2021 6:22 pm
If 2 channels are sufficient DAC8552, but 16-bit only https://www.robotshop.com/de/de/raspber ... gL0ffD_BwE

Everything else on google search for raspberry pi dac hat is audio. Don't think what you're up for is available as it is too niche.

Thank you! Yes, this is one of the closes I was able to find, too. It is actually very close, 16 bit and relatively accurate DAC with settling time around 10us (probably not good enough to make 100ksps but very close).

Just in case someone will be looking, I also found:
https://store.ncd.io/product/ad5696-16- ... ni-module/

It is 4 channel converter working over i2c with communication speed of 400kHz. Unfortunately, 400kHz clock is not sufficient to meet 4 ch x 100kSps but it also might be very useful for some other applications that people will have for lower speeds and DAC is more accurate than above 2 channel board.

Unfortunately, this both still not good enough for our project. May be you are right and we are looking for very niche product that is not there and is over specified for most people needs. But may be above information will also help some people to shorten their path to the solution.

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