I'm not so sure about the temperature stability of the default (DRS4 internal O-OFS) value, that's why I used a precision DAC in my design. But actually I never tried without. Probably the default internal value is good enough if you calibrate each chip (which you do anyhow).

Most designs use no filter between DRS4 and AD9222. Since the DRS4 output is BW limited at around 50 MHz, there is not much you win if you put a 32.5 MHz low pass there. And the PCS gets just so much simpler.

You are right with the latency of the AD9222, this is an issue. From the remaining 81 ns you loose a few going out of the FPGA, you need one or two FPGA clock cycles to make the decision, the DRS4 has also some stopping latency (maybe 10 ns). So you are at the edge. Some people use hardware comparators which are faster than the AD9222, one guy uses even directly an LVDS input of the FPGA "mis-used" as a comparator, where the comparator level (=LVDS negative input) comes from a DAC.

- Stefan

 Like Stefan pointed out, your time constraints are quite tight. In those 81 ns, you also need to deserialize the AD9222 output. Unless you implement some really fancy input comparison logic, this will consume another 1-2 ADC clock cycles. Perhaps you should first verify that your FPGA design actually can do its job within those 81 ns. In our system, we sample at only 1-2 GHz and have enough margin to implement really complex triggers in FPGA. But the total latency (ADC + FPGA deserialization) takes 250 ns.

Depending on the application, you do need a low-pass filter. Not only because of the noise, but also in order to be able to trigger reliably. Using fast PMTs for example, you will not be able to see all pulses in full size if the bandwidth is 50 MHz and you're only sampling at 65 MSPS.

Hannes

Thank you for your answers,

Another question : Have you ever tried to split the differential signal at the output of the DRS4 chip ? For example to feed both an AD9222 and a diff. amplifier (followed by discriminators) ?

Yes. Just have a look at the schematics of the evaluation board. This is exactly what is done there.

Actually in the newest version we went one step further and put the comparator at the input of the DRS chip. This way it is active even during the readout of the DRS4 chip and we can use this as a counter to count the overall hit rate at the input.

- Stefan

Hi,

I wish to interface the DRS4 with the 8-channel ADC AD9222 (or AD9637).

I'm reading from the DRS4 datasheet that "the analog output of the DRS4 chip has been designed to match directly the input of the AD9222". OUT+ output of DRS4 is in the range from 0.8V to 1.8V and OUT- output is shifted by the voltage applied to the O-OFS pin.

The span of the AD9222 ADC core is defined by REFT and REFB which are resp. 1.4V and 0.4V in a typical case (AVDD=1.8V, VREF=1V). My understanding is that the ADC analog inputs must be within the voltage range defined by REFT and REFB and so I don't quite see how this matches the DRS4 outputs.

Can we use the full-scale range indeed? Do we have to use AC-coupling with mid-supply bias? What is the point I missed?

Thank you for your help.

Dear Stefan,

I am trying to setup DRS inside radiation enclosure and would like to write a simple script that will automatically save certain number of events.

Could you please point to me an example that can I use for Mac OS? I saw there is drs_exam.cpp in the directory but was not able to get work in Mac OS. Any help would be greatly appreciated.

Thanks

Dear Maksat,

If your car does not run, and you call the car dealer and tell him "my car does not run", what will the car dealer ask you? Eh... ? Right ! He will ask "what are the symptoms, what did you try, what did and what did not work". Here it's the same. "was not able to get it work" is not a valid statement, since I have absolutely no idea what did not work and what you did try.

The official way is to follow the instruction in the evlauation board manual on section 2.4 - Installation under Linux. If that does not work, please be a bit more precise what errors you get.

Cheers,
Stefan

I am having a general problem getting read back using the ROI mode.  In the transparent mode everything looks good. These are the steps that I take:

1) configure register (b"11111111",addr = "1100")

2) configure write shift register (b"11111111", addr = "1101")

3)  assert DENABLE and DWRITE

4) wait for trigger

5) on trigger deassert DWRITE

6) Strobe RSRLOAD

7)Set drs4 address to enable all channels (address = "1001")

8)give n SRCLK pulses

9) goto 3 and repeat.

Am I missing something? Everything looks straight forward based on the manual yet in the readout mode I only get noise. I do get the stop position on SROUT and the refclk is at 475 KHz as desired and I get the desired behaviour  for DTAP toggling at the same frequency as refclk.

Uhh, there are 1000 things which might be wrong. A bit like "my car is not working, it makes strange noise". Without having a look under the hood, there is just some wild guessing:

- Is your ROFS input at the right value? Your O-OFS?

- All VDD voltages there? Input voltage outside the rails?

- Your RSLOAD pulse long enough (>10ns)

- What happens if you put a really big sinal at the input, like 100 MHz sine wave with 2V p-p

The easiest is to have a look at the evaluation board and copy your new board like 1:1, also copy the VHDL readout code. Much easier that to start from scratch.

Stefan

Thanks for replying Stefan.

I was more so just concerned with the steps in the firmware when I had asked. However, yes the ROFS (1.05V) and O-OFS (0.9 V was 1.3 V earlier but, changed this becasue of ADC input requirements) are per spec, the VDD voltages are all there and input voltages are within the rails and finally the RSLOAD  (16 ns) too is ok. Looking at your eval board firmware , on appearance it looks exactly like what I am doing. I thought maybe I was/ still am missing some intermediate addressing stage. What I wrote earlier is what I still have.

No, I can't think of anything else. There is no intermediate addressing stage. The only thing which sometimes happens is that the QFN76 package is not soldered correctly. If you don't have this under control, some pins might have a bad contact. You can check this by touching with a oscilloscope probe not the PCB pads but really the pins from the side, which is a bit tricky.

Stefan

Hello,

I am writing a VHDL code to drive a DRS4 chip.

In order to configure the DRS4 chip, I have to set the "Config Register" and the "Write Shift Register" then ... (I do not plan to use simultaneous WR and R so I guess the Write Config Reg. is not needed)

My question is :

When do we have to perform a "Read Shift Register Initialization" ?

Every time before a full read-out, or juste once after a DRS4 reset ?

Further more, is this initialization needed for the ROI mode ?

And at last do the level of the DENABLE and DWRITE signals matter for the "Read Shift Register Initialization" ?

(To sum up : what is the purpose of the Read Shift Register and how does it work ?)

Cordially,

G.Blanchard.

There are two readout modes "Full Readout Mode" and  "ROI mode". 

In the Full Readout Mode, the Read Shift Register has to be initialized before the first readout by applying the sequence shown in Figure 11 in the data sheet. This clears the full shift register and sets the first cell to "1". In principle in the following events one applies each time 1024 clocks. Since the shift register is circula, the single "1" rotates through the shift register and is at the same position after 1024 clocks. So in principle the register does not have to be re-initialized. To be hones I have never tried this myself, so I'm not completely sure if that works.

In the ROI mode, you initialize the Read Shift Register by a single RSRLOAD pulse as shown in Figure 15. Since the inverter chain stops at different positions in each event, this pulse has to be applied before each event. The SROUT bits will then tell you where the inverter chain has been stopped.

Most people I know of use the ROI mode, since the initialization is much simpler (just a single pulse).

Best regards,

Stefan

Dear experts,

I would like to use DRS4 evaluation board as DAQ system for small, table-top experiment.

I need waveforms capture as binary file on some trigger based on command line without GUI.

I found `drscl` tool in official software, but it require interactive command. I'd rather use static macro or so on to control DAQ as same behaviour in each time.

I guess, experts are thinking users should develop DAQ code by themselves for their experiment specifically, but my request is very common so someone has already developed these tool.

Best regards,

Keita

There is an example program in the distribution under software/drscl/drs_exam.cpp which is a stand-alone program to do what you need. It uses the C library coming with the distribution. It configureres the board, defines a trigger, and then writes a few waveforms into a file. You can use it as a starting point for your development. If you need any other language, you have to develop bindings to the C library.

Stefan

Thank you very much. That is what I wanted.

Hi, I have a DRS4 v5 evaluation board and I have a novice question about the oscilliscop application. When I connect it to a photo-detector (silicon photo-multiplier to be exact), the signal appears only on one half of the screen, and I cannot change it to be full screen, and pulse to be centered. I tried changing delay time and played around with the settings of the applicaton but no success. I'd apprecite if someone help me on this, probably very simple, problem.

There is a horizontal position slider in the "Horizontal" box on the right side below the trigger delay. Use it.

I am trying to use 4 evaluation boards with a powered USB hub (since eventually, I will have to do this on a laptop).  It seems like destroying the DRS object is insufficent to properly close the boards when on the hub (i.e. I get usb read errors next time I run my program). When all the boards are plugged into the computer, all is fine.  This is on Linux using libusb1. My guess is something about resetting the port doesn't work properly (but maybe that's this particular hub's fault?).  Has anyone else experienced a similar issue. If not, can someone recommend a hub that is known to work?

Hi,

I`m trying to calibrate my DRS4 evoluation board to an input range of 0-1V but it doesn`t work.

1) First I tried to calibrate it with the drsosc (version 5.0.3) Software. The -0.5V - 0.5V calibration works, but during the 0 - 1V calibration the Software crashes.

2) I also tried to calibrate the input range with a C++ DAQ Package (based on drs_exam). Here the code of the calibration:

    ....

    b->SetInputRange(0.) (Center at 0 V )

    b->CalibrateVolt(NULL);

   ....

   Calibration Works

   ....

   b->SetInputRange(0.5) (Center at 0.5 V )

   b->CalibrateVolt(NULL);

  ....

   Results in: Found 4096 stuck pixels on this board.

Did I do a mistake or is this a normal behaviour of the board? Also the board often crashes and I get a magic number 0000 after restarting the DAQ. Then the board needs to be restarted via pulling the plug. ( I ensured that I terminate the USB connection before I close the program with "delete drs"). Is there a possibility to avoid this error?

My OS: Ubuntu 14.04 LTS.

Ciao,

Julien