Redpitaya Forum

Hi all

In the webapp of the Cal scope the time line can have a big area ( up to 500seconds an more) but my graph stops at 9 second is that normal? how can i see a bigger area on my desktop?

greez kuengla

Hi !

I have never used this app, but 500s it seems very huge ! Even 9 second ... How many points does it represent ?

Hi see the attachments at +- 9seconds it stops and if i download the data traces it stops at +- 1 second

What is your sampling frequency ? 125MS/s ?

I dont know it must be the default value

So it should be 125MS/s.

With this sampling frequency, in 1 sec you acquire 125,000,000 points. Data are acquired on 14 bits ==> 2 octets. The size of the buffer is 250,000,000 octets ==> 238,42Mo.

It is strange, because it means data are transfered into the RAM. I'm maybe wrong but I don't think so

yes i understand it i can't see more becuase 8.58 second is the time i can reach with the maximum decimation =)

So it is normal.

Why ?

Because, the max decimation is 65,356 (cf. acquire.c). So you have a Fs = 125,000,000/65,536 = 1,907.348Hz
And, you have a FPGA memory size of 16,384 points. So it is equal to a time of 16,384/1,907.348 = 8.589s

This is the explication. You have to read all the data which are saved into the FPGA memory before saving news data. Or, the other solution is to use the RAM so save data ^^. But without it, I don't think you can read data in streaming.