Products > FMC150

Understanding Fmc15xAPP

(1/3) > >>

JoaoFerreira:
Hello,


after reading all the documents and trying to understand all the code of Fmc15xAPP, i'm now trying to change this APP to make it do the things that i want.


What i want to do is to input a sinewave in the ADC0 and retrieve it in DAC0 output. So i came up with a method but i don't know if i can do it like this or if i have to change the firmware first.


Method:


1 - Enable ADC0 and DAC 0 using the function " fmc15x_ctrl_enable_channel() "
2 - ARM DAC0 and make ADC FIFO ready to store data after a trigger event using "fmc15x_ctrl_arm_dac()"
3 - Send a trigger event to ADC0  using "fmc15x_ctrl_sw_trigger()"
4 - Load new data in the DAC WFM using "fmc15x_ctrl_prepare_wfm_load()"


My method is in the right way or i really have to change the firmware?


Other thing that i have a doubt is about the max and min input voltage, in the FMC 150 user manual it says that the input voltage range is 2Vp-p, this means that for example the max amplitude of my sinewave is 1V?


Thanks in advance

lmunoz:
Hi,

First keep in mind that the ADC is going at 250 Msps 14-bit and the DAC is going at 800 Msps 16-bit, so if you just capture ADC data and send it to the DAC you might not get the output you expect.

You can capture data from the ADC to the host computer then upload it to the DAC using the method you describe, i.e., using the functions provided. This is not in real time, you have to change the firmware for that.  But again you will probably not get the expected output without doing some signal processing on the data because of the different sampling rates and the discontinuity.


2Vp-p means the signal oscillates between max 1V and min -1V because it is AC coupled.
 

Regards,
Luis

JoaoFerreira:
But what i want is to input a sinewave in ADC, put the data from ADC in a BUFFER and then input that data in the DAC and get the output from the DAC to an oscilloscope to see if the input sinewave is correctly processed by the ADC and DAC.

So i think using the method i explained, in the previous post, i can get what i want because in the FMC15xAPP code provided the ADC is working 250 MSPS and the DAC at 125 MSPS if i'm not wrong. And as my input will be a 30 MHZ sinewave i think there i'll not have problems or will i have??

Thanks for the help
Joao

arnaudNL:
Joao,


You are trying to change FMC150 star to be streaming. Generally removing wave form memories, increasing the data bus width or clock, etc..


As Luis explained, you will need to make sure the ADC samples are aligned properly for the DAC.


According to Nyquist, you would need 60Msps in order to sample a 30MHz signal.


These aspects are really outside the scope of standard technical support. The reference design is doing the reverse way round, output something from the DAC, loopback that to ADC (using loopback cables) and making sure what we sample is correct.


I hope that helps,
Arnaud

JoaoFerreira:
So basically what you are saying is that i have to change the firmware of FMC150 star to do what i want, right? And to do that i have to change the VHD sip_fmc150 file?


I know that according to Nyquist, i need 60Msps in order to sample a 30MHz signal, that means the DAC should work at that frequency not bigger or smaller? And the ADC should work at that rythm too?


I know that thus is outside the scope of standard technical support and i really appreciate the help you gave.


Best regards,
Joao

Navigation

[0] Message Index

[#] Next page