Hi Steffan,

       In DSR4 DATASHEET Rev.0.9 Page13,  there is a paragraph "If the DRS4 is configured for channel cascading or daisy chaining, it is necessary to know which the current channel is where the sampling has been stopped. This can be
determined by addressing the Write Shift Register withA3-A0 = 1101b and by applying clock pulses to the SRCLK input ...".

       My question is the timing details about srclk, srout, A3-A0 in the above control and its timing relation with stop shift register (Figure 15).  And can this configuration be used in the full readout mode with output MUXOUT?               

Best Regards,
Danyang (sun2222@mail.ustc.edu.cn)

Hello,

We want to use the inner DRS4 counter(scaler) within more than the 100ms integration time. We guess that we need to modify the original firmware around this point:

-- Reference clock used for frequency counter
 
  proc_1hzclk: process(I_RESET, I_CLK33)
  begin
    if (I_RESET = '1') then
      drs_1hz_counter(31 downto 0)          <= (others => '0');
        drs_1hz_clock                         <= '0';
        scaler_reset                          <= (others => '1');
        scaler_ff_reset                       <= (others => '1');
    elsif rising_edge(I_CLK33) then
      drs_1hz_counter                       <= drs_1hz_counter - 1; -- count down
        scaler_reset                          <= (others => '0');
        scaler_ff_reset                       <= (others => '0');
      
      -- toggle refclk if timer expires      
      if (drs_1hz_counter(drs_1hz_counter'high) = '1') then
        drs_1hz_clock                       <= not drs_1hz_clock;
        drs_1hz_counter(31 downto 0)        <= X"0016E35F";     -- 1499999, I_CLK33 is actually a 30 MHz clock
          
          scaler_ff_reset                     <= (others => '1'); -- reset scaler_ff once every 100ms cycle
        loop_scaler_reset : for i in 0 to 5 loop
          if (scaler_ff(i) = '0') then                          -- no activity since last cycle?     
               scaler_reset(i)                <= '1';             -- force clear scaler register
            end if;
        end loop;

          if (scaler_ff(0) = '0') then                            -- no activity since last cycle?     
            scaler_reset(0)                   <= '1';             -- force clear scaler register
          end if;
          
      end if;  
    end if;
  end process;

Could you please tell us how to modify the firmware to increse the time up to 5 seconds for instance?

Thanks in advance, Arseny

Is a 5 GSPS oscilloscope suitable for use with Silicon surface barier detectors?

Is DRS4 suitable for use with Silicon surface barrier detectors?

Aha -- many thanks.  I think what tripped up my test logic is that the "done" state in drs4_eval5_app.vhd that executes post-readout sets DWRITE back to 1 (drs_write_set).  If one then writes to FPGA register 5 while the FSM is in the "idle" state, the conf_strobe and wsr_strobe states occur with DWRITE and DENABLE both asserted.  This is if one sets the "dactive" bit in the FPGA app code, which is probably not the usual use case.  Maybe using the real DRS.cpp avoids this situation.  (I was simulating your FPGA code to test my understanding of what our FPGA code should do.)

Anyway, our own use case is fine: as you suggest, we leave DENABLE asserted, but we deassert DWRITE while reading out or while changing DRS4 register values.

Thanks again,

Bill

Hi Bill,

you keep DENABLE active all the time to keep the Domino Wave running, but you deassert DWRITE if you change any register via SRCLK. There is no shadow register, just a simple shift register, but with DWRITE being low, the domino circuitry does not touch it.

Best,
Stefan

Hi Stefan,

We have for some time now been using custom firmware on a custom board to read waveforms out of DRS4 chips.  Now we are working on cascaded readout mode, 4 channels @ 2048 samples, WSREG=0x55, in order to allow for longer trigger latency.

Doing a testbench simulation of the FPGA code raised a question for me:  Do I need to deassert DENABLE while I shift a new 8-bit value into the write-shift register?  What happens if, during the few-hundred nanoseconds it takes to shift 8 bits into the register, the domino wave crosses cell 768, thereby shifting the write-shift register left by one bit?  Is this shifting suppressed when A=0b1101?  Or does the update of the actual write-shift register occur only once, after the 8th SRCLK cycle?  (Maybe one is really shifting bits into a shadow register that is copied all at once into the actual register?)

I notice in simulating your drs4_eval5_app.vhd that if one sets bit 27 ("drs_ctl_dactive") of register 0 (do not deassert DENABLE on trigger), then starts the domino wave (set bit 0 of register 0), then issues a software trigger, then later writes to register 5 (config register, wsreg, etc.), DENABLE is not in fact deasserted during the time when A=0b1100 (conf_setup, conf_strobe) or when A=0b1101 (wsr_setup, wsr_strobe).

But my simulation testbench includes a simplified Verilog model of my interpretation of the DRS4 data sheet, and my simulated DRS4 happened to cause the write-shift register to shift (256 samples before DTAP toggled) during your "wsr_strobe" FSM state, thus corrupting the value that was being shifted into the WSREG via SRIN and SRCLK.

So I'm curious:  to be safe, should one deassert DENABLE before updating the write-shift register, or is it safe to update it even while the domino wave is active and looping?  It seems easy enough to be safe, since we should only need to write to the WSREG once during the setup phase and then let it loop forever.

Many thanks,

Bill

The DRS4 input is high impedance. So if you like you can terminate it with 100 Ohm differentially and route it with 100 Ohm. But if you keep the lines short, the reflection is negligible. That’s what we made on the evaluation board.

When you're refering to laying a 50 Ohm trace, you're referring to the SMA input and not the interface between the output of the Op-AMP(THS4508) buffer 
and the inputs  of the DRS4(IN0-IN8). Is there a recommended diffential impedance for IN0-IN8? 

Ismael

The requiremnet is the same as for any high speed analog board, there is othing special with the DRS4. If you want to terminate your line with 50 Ohms and you want a matched impedance layout, you route all lines with 50 Ohms impedance. Truth is however that nothing is perfect. The SMA connector is not exactly 50 Ohm, the PCB gets a 10-20% variation depending on the manufacturer. So even if you try hard, you will never have a 50 Ohm matched impedance. On the evaluation board we made some compromises as you have seen, but for us the board works satisfactory even with this compromises, and you can test it yourself with real hardware (namely the evaluation board). If you can do a better job, try it. But usually these compromises have only little influence on the signal quality.

Stefan

Hi Steffan,

              I'm an engineer at UCLA developing a board with the DRS4 chip. Our team has a question on what might be the required trace impedence for the analog inputs. Can that information be provided? 

Best Regards,
Ismael Garcia

Hello Stefan, 

Thanks for the quick reply. The issue was a faulty SMA connector, should have checked this first. Signal looks good now.

Thanks for your time, 

Brendan

Have you set the trigger correctly to the channel with your signal, polarity and level? Do you undersand the difference between normal and auto trigger? Why don't you post a screendump. Are you ABSOLUTELY SURE that you have a signal on your cable? Have you tried with another oscilloscope? Are you sure that your SMA connector is good?

Stefan

Hello, 

I have recently obtained a DRS4 Evaluation Board (V5), but I am unable to register signals when using the DRS Oscilloscope application. There seems to be some difference in noise when I have an input connected to a signal or not, but I am unable to view a simple, 0.2V amplitude square wave or other small signals. The only way I have been able to view a waveform is when connecting the reference clock to all channels. When running 'info' in the DRS Command Line Interface I am shown correct information. I was wondering if there is any way for me to test the functionality of the board (specifially ability to read signals on Ch 1-4) to ensure that it is indeed working as expected? 

Thanks, 

Brendan

Actually in the original drs_exam.cpp the sine wave oscillator is turned off with this command

/* use following line to turn on the internal 100 MHz clock connected to all channels  */
//b->EnableTcal(1);

If you remove the "//" then the generator gets enabled. Probably you did this by accident. With this line commented out, you see the proper input like this:

Event #0 ----------------------
  t1[ns]  u1[mV]  t2[ns] u2[mV]
  0.000     1.9   0.000    -2.4
  0.195     0.5   0.195     0.3
  0.391     0.1   0.391    -1.4
  0.586    -0.7   0.586    -0.4
  0.781    -1.1   0.781    -2.4
  0.977    -0.6   0.977     0.0
  1.172    -1.5   1.172    -2.8
  1.367    -0.4   1.367    -0.6
  1.562    -1.2   1.562    -3.8
  1.758    -1.5   1.758    -1.7
  1.953    -1.0   1.953    -3.3
  2.148    -0.7   2.148    -1.8
  2.344    -1.6   2.344    -4.2
  2.539     0.5   2.539    -1.5
  2.734     0.2   2.734    -3.6
...

167.969    -3.4 167.969    -5.2
168.164    -3.7 168.164    -3.6
168.359     0.0 168.359    -2.0
168.555     1.9 168.555    -0.2
168.750     2.8 168.750    -2.8
168.945     5.4 168.945    -1.4
169.141    18.0 169.141     1.2
169.336    26.6 169.336     2.7
169.531    46.2 169.531     0.4
169.727    56.2 169.727     1.6
169.922    93.3 169.922     0.1
170.117   115.6 170.117     0.0
170.312   174.4 170.312    -1.5
170.508   206.9 170.508    -0.8
170.703   282.2 170.703    -2.4
170.898   328.4 170.898    -1.2
171.094   419.6 171.094    -3.2
171.289   465.8 171.289    -2.5
171.484   500.0 171.484    -2.0
171.680   500.0 171.680    -0.6
171.875   500.0 171.875    -4.0
172.070   500.0 172.070    -1.1
172.266   500.0 172.266    -3.7
172.461   500.0 172.461    -2.1
172.656   500.0 172.656    -5.0
172.852   500.0 172.852    -3.3
173.047   500.0 173.047    -4.8
173.242   500.0 173.242    -4.1
173.438   500.0 173.438    -5.1
173.633   500.0 173.633    -3.3
173.828   500.0 173.828    -6.4
174.023   500.0 174.023    -3.9
174.219   500.0 174.219    -5.5
174.414   500.0 174.414    -3.2
174.609   500.0 174.609    -3.6
174.805   500.0 174.805    -2.6
175.000   500.0 175.000    -5.2
175.195   500.0 175.195    -2.7
175.391   434.3 175.391    -3.9
175.586   391.7 175.586    -2.4
175.781   312.2 175.781    -4.1
175.977   275.7 175.977    -1.8
176.172   202.4 176.172    -3.8
176.367   167.6 176.367    -1.4
176.562   117.4 176.562    -2.9
176.758    96.1 176.758    -2.3
176.953    62.8 176.953    -3.3
177.148    49.1 177.148    -1.8
177.344    35.9 177.344    -4.3
177.539    33.4 177.539    -2.6
177.734    30.4 177.734    -4.2
...

Hi Rodrigo, I'm wondering how you solved your original triggering problem. We are also having trouble with collecting data continously using the example. Thanks.

I see. Where is the code that we can use to turn off the generator? I thought the example is taking data with CH1 as the trigger.

For our board, which is BoardType == 9, it is running these lines:

      b->EnableTrigger(1, 0);           // enable hardware trigger
      b->SetTriggerSource(1<<0);        // set CH1 as source

Is that not using the hardware trigger with CH1 as the source?

Sure, that’s correct. The example program turns on the internal sine wave generator in case people don’t have a real signal. That’s why it’s called „example“. Find the code which turns on the generator and change it. You will also have to change the trigger settings depending on your actual signal.

Stefan

We are using the drs_exam.cpp to read out waveforms, but it seems to be outputting only sin waves on all channels - as if it was reading out the simulated waveform from the oscilloscope program if we run it without the board plugged in. Does anyone know what is causing this?

We are taking data with a pulser plugged into channel 1, which produces a single pulse with width of 8ns, and nothing plugged into channel 2. 

Our board is as follows:

Found DRS4 evaluation board, serial #2567, firmware revision 21305
Board type: 9

The output is something like the following:

Event #0 ----------------------
  t1[ns]  u1[mV]  t2[ns] u2[mV]
  0.000  -452.7   0.026  -469.3
  0.289  -460.8   0.293  -469.8
  0.413  -477.3   0.400  -481.5
  0.642  -485.3   0.650  -482.4
  0.806  -486.9   0.821  -477.8
  1.086  -476.8   1.085  -457.2
  1.183  -467.3   1.162  -446.4
  1.450  -435.6   1.459  -405.1
  1.619  -410.1   1.630  -373.3
  1.843  -366.2   1.851  -323.9
  1.945  -342.9   1.948  -298.9
  2.221  -275.7   2.210  -229.3
  2.359  -237.6   2.357  -187.6
  2.602  -165.6   2.609  -111.2
  2.687  -141.1   2.697   -84.3
  2.976   -50.5   2.987     5.5
  3.164     8.4   3.144    53.3
  3.377    73.9   3.384   124.2
  3.503   111.4   3.506   158.0
  3.753   182.0   3.769   226.9
  3.924   227.5   3.929   265.8
 

Dear Stefan, 

Thanks so much for clarifying this. We made wait_vdd a parameter controlled by software and will try to experiment with it to find some compromise between deadtime and the offset added by the droop in VDD. 

Best regards, 

Andrew