Hello,

I work with the DRS4 Evaluation Board V5 and I have a problem with the software.

Thanks for the help.

Rebecca

Can you post a screenshot where I can see the channel waveforms, the configuration and the trigger settings?

Stefan

Hello,

It seems that a coincidence with two fixed channels suddenly works. I don't know why.

Screenshot 1 shows the trigger settings for the coincidence with two channels.
Screenshot 2 shows the oscilloscope surface.
Screenshot 3 shows the configuration. In the background there is a coincidence with three channels.

In contrast to the coincidence with two channels this doesn't look good.

Rebecca

Hi,

from our screenshots I see the following:

- you have sometimes a huge oscillation in your preamplifier. Fix this first before doing any waveform recording

- your signals are barely 20 mV, and your trigger threshold is 20 mV. The coincidence only triggers when both signals are below the trigger threshold at the same time, and the overlap must be longer than 4-5 ns. So if your signals  are not exactly in time, you won't get a coincidence trigger

Stefan

 Hi, I read its possible to use channels 2,4,6 to extend 200ns to 400ns (1024bins to 2048).

Is it possible to use same channels to double sampling rate with paralel feeding, one channel delayed by Ts/2, for 5,12GS/s is it cca 3cm delay cable?

Martin

In principle yes (you could split your signal externally and add some cable delay to one side), but it is not supported by the software. You would have to combine the data from the two channels yourself. But it won't help much. The analog bandwidth of the evaluation board is about 700 MHz. So sampling at 10 GSPS vs. 5 GSPS won't give you any additional information, since the highest frequencies in your signal will be only 700 MHz. You could as well take your 5 GSPS measurement and interpolate it with some sinc function to get exactly the same result. See here for details: http://en.wikipedia.org/wiki/Whittaker%E2%80%93Shannon_interpolation_formula 

Good news for all DRS4 users. After many years, I finally understand where the "symmetric spikes" come from and how to fix them.

The "symmetric spikes" are small spikes of 17-18mV, which randomly happen at 1-2 cells. They alwas come in groups of 2 in each channel, symmetric around sampling cell #512. See first attachment.

The reason for the spikes is the previous readout cycle. On each readout cycle, the "read bit" is clocked through all 1024 cells to switch one cell contents to the DRS4 output. At the end of the 1024 cycles, the read bit stays at its last position. The bit is carried by a metal line on the chip, which crosses all 9 channels (second attachment). This bit now influences the sampling cells below the metal line capacitively, so their contents is "pushed up" by a few mV, just like the ROFS offset does. Since the DRS sampling channels are in a snake layout, going 0-512 from left, then 512-1023 back again, the line crosses two cells in each channel, and thus the symmetric spikes.

Previously, there was a software solution for that. In the evaluation board software DRSOsc there is a button "Remove spikes" which tries to fix this in software. Although this works most of the time, it's annoying and not 100% safe. Like when the spike sits on top of a noise signal, it might not be recognized. Fixing this in hardware is however straight forwar. After the readout cycle ends, push the read bit out of the chip:

• Address the read shift register by applying 1011b to A3:A0
• Switch SRIN low
• Apply 1024 clock cycles to SRCLK

This shifts the bit out of the chip, so that the next event is not affected by the read bit. The third attachment show the effect of this. The "clear cycle" increases the readout time a little bit, but depending on the application this might be worth it.

Regards,
Stefan

Hi,

Is it possible to fix it by FPGA changes?  I see readout cycle (proc_drs_reedout) in drs4_eval(4)5_app.vhd, but not sure where to exactly put this three commands. Could you please attach app.vhd file for eval board with example how to fix ?

Regards,

Martin

Yes it's possible, but I have to find time for that. The software of the evaluation board takes care of the spikes ("remove spikes"), so I thought it's not so urgent to fix that in the FPGA (which takes me some time).

Stefan

Ok, so I made it ... and Yes it works :), 

https://youtu.be/0noy4CoFoh8 

here is changed part in drs4_eval4_app.vhd

               
        when done =>
          drs_readout_state    <= spikeoff;
          drs_stat_busy        <= '0';
          drs_dpram_we1        <= '0';
          drs_write_set        <= '1';   -- set drs_write_ff in proc_drs_write
                                         -- to keep chip "warm"

 -- spike fix ELOG 697        
 
          when spikeoff => 
            o_drs_addr       <= "1011"; -- Address the read shift register by applying 1011b to A3:A0
            o_drs_srin       <= '0'; -- Switch SRIN low             
             drs_readout_state                 <= spikecycle;
             -- Apply 1024 clock cycles to SRCLK     
             drs_sr_count         <= 0;

          when spikecycle =>      
             drs_sr_count         <= drs_sr_count + 1;
             o_drs_srclk          <= not o_drs_srclk;
             if (drs_sr_count = 1024) then
                drs_readout_state <= idle;
             end if;      

        -- set-up of configuration register        

 Hi, Stefan, I see in your ppt "Design and performance of 6 GSPS waveform digitizing chip DRS4" , you define DRS4 ENOB as 1Vpp/0.35mv(RMS) = 11.5bit, where, 1Vpp is the linearity input range, and 0.35mv is the rms voltage after offset correction. What I understand is that 0.35mV is obtained from DC offset Correction, hence 11.5 bit is for DC input, am i right?  If true, what about ENOB for AC input in the whole analog bandwidth?  thanks~

The expression ENOB for 1Vpp/0.35mV(RMS) is wrong, but I learned this later. Now I call it SNR. The ENOB is calculated in a more complicated way, see for example http://en.wikipedia.org/wiki/ENOB. If you measure the ENOB without timing correction, it's pretty poor (in the order of 7-8 bits). This is because without timing calibration, a sine input has huge side bands, and the ENOB involves the power of your signal over the power of the side bands. If you do a proper timing calibration, you spectrum gets "sharper", and hence the ENOB increases. But I have to admit that I never measured it carefully, since we are still optimizing the timing calibration. Once we have a perfect timing calibration, I will do it and update the data sheet. 

Hi

I have a question about the function SetTriggerSource in the class DRSBoard (DRS.h/DRS.cpp)

In the implementation there is the following comment:

// Set trigger configuration

// OR 0=CH1, 1=CH2, 2=CH3, 3=CH4, 4=EXT

// AND 8=CH1, 9=CH2, 10=CH3, 11=CH4, 12=EXT

What does this exactly mean? I am assuming that this are the bits which are set?

e.g

source = 1 ==> CH1

source = 4352 = 0x1100 ==> CH1 and ext

How is the AND/Or logic implemented?

When i have:

source = 0x1803 (bit 12,11,1,0)

what is the right way to set the brackets to expalin the logic?

(EXT and CH4 ) or CH2 or CH1 ?

Cheers Felix Bachmair

ETH Zurich

Your first assumption is correct, e.g.

source = 00000000'00000001 = 0x0001 ==> CH1

source = 00010001'00000000 = 0x1100 ==> CH1 and EXT

So the lower byte is the "OR" block, and the upper byte is the "AND" block. Both blocks are combined via an "OR" so

source = 00011000'00000011 = 0x1803 is (EXT and CH4) OR (CH1 or CH2)

The "OR" combination between the two blocks is fixed in the firmware and cannot be changed without changing the firmware, but theoretically any logical combination between five inputs would be possible if you touch thr firmware.

/Stefan

Hallo,
I'm using DRS4 Evaluation Board Rev 4.0 and I'm trying to change the output of the samples to be an average of  #  measurements (1000 or even more)
during the process I have encountered some difficulties I hope you will be able to help me  with:

1. the DRS chip have 8 channels but the Evaluation board have only 4 channels. does the default mode of the DRS in the Evaluation Board is 1024 bins for each channel or 2048?

2. in the readout mode, does it samples all the 1024 bins waveform from a channel and then move to the next one, or after each bin it move to the next channel?

3. In the file "drs4_eval4_app.vhd", I have a problem finding the names of the signals that represents the registers bits which tell me what is the number of the bin (1-1024) the ADC is reading from the DRS, and the signals

that represents registers A0-A3. can you send me their names? 

4. In another matter- is the -0.5V to 0.5V is the  upper and lower  limit of the input (or just a working range), and if not what is the limit for AC?  is there a fuse on the board in case of overload from the input? (I didn't see  it in the User's Manual, but I didn't know if you will mention it there in case there is one).

thanks in advance and have a nice day,

Tmiron

1. All 8 channels are read out, but only 4 are displayed in the oscilloscope.

2. It reads all 1024 bins from a channel, then switch to the next channel.

3. The ADC readout happens in lines 1576+. The register for the sample count is drs_sample_count, and the signal for the address is drs_addr.

4. The evaluation board manual explicitly mentions the maximum allowed input range on page 5.

/Stefan 

  Hello everyone！I'm a new user of DRS4 board,but it seems that some files are missing in my demo project.So I hope someone could help me by sending a correct VHDL hardware project to my Email:lcyiss900@gmail.com.Thanks in advance!

T

 I checked my project today and I think I need the file USR_LIB_VEC_IOFD_CPE_NALL.I don't know if is it a VHD files or a IP core.

I'll be extremely grateful.

 USR_LIB_VEC_IOFD_CPE_NALL is defined in firmware/srs/usr_lib.vhd which is part of the software package.

Hello Stefan,

I just stumbled again over a phrase in the DRS4 datasheet I never really understood, but didn't find the time to ask.

On page 8 it says: "An internal circuit ensures that the write signal is always 16 cells wide."

So when I look at a single channel, do I understand correctly, that at any given time during sampling, always 16 cells are open, i.e. 16 cells are connected to the analog inputs? So when the domino frequency is e.g. 5GHz then each cell sees the analog input not for 200ps but for 3.2ns correct?