ADC implementaion in DE2-115

[vrvrao]

Hello,

I am newbe to FPGA, we are using DE2-115 Developmental board.

For a task we need to transfer data from sensor to DE2-115, for which we need ADC.

In DE2-115 user manual we can see Audio Codec ( 24 bit), can we use this as an ADC, please let me know if there is an example or any pdf about it.

Thanks,

Raja.

 

[mrflibble]

What codec? And what does the datasheet for that codec say? Or the documentation for your dev board for that matter...

 

[vrvrao]

Hello Mr flibble,

thanks for your reply, and sorry for replying lately.

What codec? And what does the datasheet for that codec say? Or the documentation for your dev board for that matter...

CODEC is 24 - bit encoder/decoder.

In dev board manual it is mentioned as, board has 24-bit audio via Wolfson WM8731 CODEC.

In Wolfson WM8731 Codec features are
Audio performance
-- ADC SNR 90 dB at 3.3 V.
sampling frequency 8kHz to 96kHz.

So, now can we use this.

thanks,
raja.

 

[mrflibble]

No worries about the late reply, that's a good thing. That means you've now had more than a week to go over documentation and with a bit of luck you have something working.

I took a real quick look at the WM8731 datasheet. The WM8731 has an SPI interface, so you can use that. SPI is pretty simple to implement in verilog/vhdl, so seems to me that would be a good starting point.

 

[vrvrao]

Hi again,

No worries about the late reply, that's a good thing. That means you've now had more than a week to go over documentation and with a bit of luck you have something working.

I took a real quick look at the WM8731 datasheet. The WM8731 has an SPI interface, so you can use that. SPI is pretty simple to implement in verilog/vhdl, so seems to me that would be a good starting point.

Thanks for reply.

Actually its I2c i think, am attching the datasheet provided along with the board. If it so, i need to implement ADC using I2c. am i right.

A query, is ther a possiblity of Implementing with EtherCAT slave.

thanks,
raja.

 

[mrflibble]

You are possibly right and wrong, all at once. I didn't check if it had i2c because who cares. I opened the pdf, did CTRL-F .. SPI ... yup, it has spi, excellent.

So quite possible that it has both I2C and SPI. And on fpga you want to implement it with SPI because that is less troublesome.

Regarding ethercat, I have no opinion. Because "there is a possibility" to connect it with just about anything. The question is not "is it possible", the question is "how difficult is it, and does it make sense given your project requirements". Does it make sense for your project? No idea, I don't know your unwritten requirements.

 

[vrvrao]

Actaully am already implementing SPI interface between the FPGA board and TI microcontroller.

Thats why, i need to look for any other possiblities.

In project is like data aquisition from voltage detection sensor --- FPGA --- TI controller. Later motor control using TI. So, in between FPGA -- TI using SPI.

for faster data aquisition thinking of EtherCAT as slave on FPGA.

does it works.

thanks,
raja.

 

[mrflibble]

Does it work? Sure, it works. And from that point on it is your work to implement it.

Anyways, what kind of bitrate do you need? I mean, if it (the codec) works over I2C it is bound to have a sucky bitrate. Translation: what kind of bitrate does the WM8731 provide, and based on that why do you think you need 40 GBPS infiniband?

 

[vrvrao]

Dear flibble,

The sampling frequency provided in WM8731 is 8 - 96 kHz.

As you said, through I2c we have very slow bit rate, and i think to control the shaft of motor continuously we need high bitrates.

P.S: You are right abt serial interface and am sorry it was I2S not I2c.

thanks,
raja.

 

[mrflibble]

Ah okay, so the choice for ethercat is driven by motor control requirements, and not WM8731 data rate. Since you said "faster data acquisition over ethercat", but I take it faster data acquisition has nothing to do with it if the WM8731 is the only thing doing the acquiring. ;-)

Anyways, if motor control is the application then ethercat sounds quite reasonable.

 

[vrvrao]

you r right mrflibble.

WM8731 is used for ADC purpose. For EtherCAT implementation , do i need to have a EtherCAt controller from Bhakoff or we can just implement a EtherCAT slave.

In ethercat slave case, is there any example available.

thans,
raja.

 

[mrflibble]

I've seen some talk about an fpga implementation of ethercat slave on some CNC forums in the past. But I've never seen an actual open source implementation.

Check for example cnczone or EMC2 project to see if there are people that would be interested to put some time into it.



- - - Updated - - -

Oh and should you find something, please post it in this thread. I might want to use ethercat in about a year or so for some projects.

 

[vrvrao]

thanks for reply.

Flibble, this is what i have an idea tell me whether am right.

1) Am using ADC implementaion to convert analog signals from Sensor to FPGA via serial interface.
In DE2-115 board, i have an RS-232 with Trans receiver ZT3232E and sensor has an RS - 232 at other end. So, can we use this interface.

2) EtherCAT is used for data acquisition, do i need to use this after ADC.

and i will look at the link.

 

[vrvrao]

Hi,

What is the difference between Ethernet MAC and EtherCAT. Can EtherCAT slave implementation is done using ethernet MAC.

thanks,
raja.

 

[mrflibble]

https://en.wikipedia.org/wiki/EtherCAT