DAC1280 Bitstream

Zhuo Peng

Intellectual 410 points

Other Parts Discussed in Thread: DAC1280, DAC1282, OPA211

Hi,

Is anybody know how to accomplish creating the bit stream file for DAC1280?

Is there any document that describes how to accomplish creating the bit stream file ?

Thank you!

over 15 years ago

0 Zhuo Peng over 15 years ago in reply to Tom Hendrick

Intellectual 410 points

Hi,

I have a question about the DAC1280 bitstream file which have puzzled me for a long time.Thank you for your atttention.

On page 12of the datasheet of DAC1280,it's said" The bitstream originates either from an FPGA-based digital modulator or playback from a ROM device holding a stored bitstream file. "

But how to make the bitstream file.If my wanted wave is periodic,can I only save a period in the file?

Could you tell me same details about how to make a bitstream file?Is there any arithmetic?

I want to make a 31.25Hz sinewave.Could you please help me to make a bitstream file.

Thank you!

0 Tom Hendrick over 15 years ago

TI__Guru**** 182601 points

Hi Zhuo,

Can I ask what your application is?

The means to create the bit stream file involves some proprietary algorithms that I can not publish here. We are looking at ways to do a web based application that allows you to input a desired frequency and amplitude and have it produce the file for you. That app is non-existent at the moment, so currently we have two alternate options:

1.) Let me know the frequency and amplitude of the signal(s) you want to create and I will see if I can have the bit stream file created for you.

2.) With a signed non-disclosure agreement, we could provide the Matlab source code to generate the bit stream files.

0 Zhuo Peng over 15 years ago in reply to Tom Hendrick

Intellectual 410 points

Hi Tom,

Nice to meet you again!

My application is for selftest on a Data Acquiring board.It's a rearch in university,somthing about Seismic Monitoring.

I want to get several frequencies,such as 25Hz, 31.25Hz, 50Hz, especially 31.25Hz. The amplitude is 2.5V.

If possible, I expect to find help in the Matlab source to get more suitable TBS for my application.

Thank you!

Regards

0 Tom Hendrick over 15 years ago in reply to Zhuo Peng

TI__Guru**** 182601 points

Hi Zhou,

For the DAC1280, I have attached an archive that contains the three frequencies you are interested in. Hopefully this will get you started. Will keep you posted on our progress with the web bit stream creation project as well as any application notes regarding the usage of the bit stream files.

Bit files.zip

0 Zhuo Peng over 15 years ago in reply to Tom Hendrick

Intellectual 410 points

Hi Tom,

I am soory to trouble you again.I still have some problem about the bitsream.

Is the bitsream periodic?For example,if I want to make 31.25Hz sinewave with the 256KHz bitsream,Can I only save 256000/31.25=8192 points in the ROM and read them out periodically.

Why the bitstream you supply in the archive is not periodically?

Regards

0 Trond Danielsen over 13 years ago in reply to Tom Hendrick

Prodigy 75 points

I'm also interested in the Matlab source code for the DAC1280. Currently we are using a simple first-order delta sigma modulator implemented in an FPGA to generate the bit-stream, but I not very pleased with the result. I'll sign any NDA needed to get access to the code.

Best Regards,

Trond Danielsen

0 Tom Hendrick over 13 years ago in reply to Trond Danielsen

TI__Guru**** 182601 points

Hi Trond,

What sort of application are you dealing with? Before we go the NDA route with the Matlab source, have you taken a look at the DAC1282? That device has very similar specs to the DAC1280, but it has on-board signal generation so you don't need to deal with the bit-stream.

0 Trond Danielsen over 13 years ago in reply to Tom Hendrick

Prodigy 75 points

The DAC1282 looks great, but unfortunately the hardware is already finished. The application is obviously one of the ones mentioned in the datasheet and on the website :-).

0 Trond Danielsen over 13 years ago in reply to Tom Hendrick

Prodigy 75 points

Hi Tom,

I decided to test these bit files on your board, but I am concerned if I am using them correctly. I assume the values in the data files are the raw byte values, and I'm clocking them out to the DAC1280 least significant bit first. Is this correct? The generated signal is saturated and very distorted long before the maximum level, but if I reduce dac gain it cleans up.

0 Tom Hendrick over 13 years ago in reply to Trond Danielsen

TI__Guru**** 182601 points

Hi Trond,

I believe LSB first is the correct way to send the bit stream - can you post a screen shot of the waveform?

0 Trond Danielsen over 13 years ago in reply to Tom Hendrick

Prodigy 75 points

Hi Tom,

I found a couple of embarrassing bugs so now it's working fine, but thanks for the confirmation regarding the bit order. Wrong endianness tend to make a mess whenever it happens...

Regards,

Trond

0 pony henry over 12 years ago in reply to Tom Hendrick

Prodigy 10 points

Hi Tom,

I want to create a sinewave with your attached bitstream files.Could you tell me the data bit in you excel files and In which way should I send these datas to the DAC1280 to produce a sinewave?

Regards,

Pony

0 Prad1 over 12 years ago in reply to pony henry

Genius 3825 points

Hi,

Any updates on the application notes and Bit stream utility for DAC1280.
We are also planning to use DAC1280 for our new project.

Regards
Prad

0 Zhuo Peng over 12 years ago in reply to Prad1

Intellectual 410 points

Hi, you can try DAC1282 which dosn't need bit stream.

0 Prad1 over 12 years ago in reply to Zhuo Peng

Genius 3825 points

Thanks...that is not possible this time as DAC1282 is $6 more than DAC1280.

The datasheet mentions that it requires around 7 pins from a controller.
But is it necessary to connect all those pins?

We would like to know if there is any example applications or circuit details
on connecting DAC1282 to a DSP/MCU.

0 Zhuo Peng over 12 years ago in reply to Prad1

Intellectual 410 points

First, the DAC1282 can output voltage so it dosen't need I/V converter as DAC1280 dose. The datasheet of DAC1280 uses two OPA211 as I/V converter which cost about $7. So if you use DAC1282, the total cost may be lower and your product may be smaller and smarter.

Second, you can find some circuit details about DAC1282 to DSP/MCU on page 35 of the datasheet of DAC1282.

0 Christian Wilde over 12 years ago in reply to Zhuo Peng

Prodigy 10 points

Hi,

we are currently running into trouble setting up a proper bitstream for the DAC1280. For a medical device (academic use) we need adaptable current output, i.e. we want to generate sine, square, sawtooth... waveforms of different frequencies and phases, such that we definitely need a proper bitstream generator. (That is also the reason why DAC1282 is not suitable for our application...) A starting point would be the aforementioned MATLAB routines. Is it possible to get a copy of these? Further correspondence can take place offline.

I really appreciate any help you can provide.

Best regards,

Christian

0 user4662991 over 10 years ago in reply to Tom Hendrick

Prodigy 10 points

Hi Tom,

I see your answer about DAC1280.

1, could you tell me the web which is create the bit stream?

2, could you send Matlab source code for me ?

my email is qgRuan@outlook.com

Thanks for you help~!

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DAC1280 Bitstream