Probe capacitance makes that tricky - if I put my probe on DSPEED, I see that it starts at approx. 2.5V then gradually decreases until it hits 0V.  DTAP decreases from 3MHz to 0 during this time.

I'll try to get something together to show you.

Can you post a scope trace of your refclk together with DTAP, DSPEED and DENABLE?

Stefan,

Thanks for responding so quickly.  Yes I have my clock source going to REFCLK+ (CLKIN is the signal name on my schematic).  BIAS is 0.7V exactly, /RESET is high, A0-A3 are 0x0000, and the loop filter has a 4.7nF cap to GND with a 130ohm resistor + 1uF cap in parallel, just like the eval board.

Regarding the clock - I am not using an LVDS clock, but rather a 2.5V-level clock signal, with REFCLK- tied to 1.25V.  Sheet 9 of the datasheet states:  If no LVDS reference clock signal is available, a CMOS signal can be connected to REFCLK+ and the REFCLK input is connected to VDD/2 via a resistor divider.

Is that not a true statement?

-Tom
 

I guess you mean "1 MHz clock at REFCLK+", and not CLKIN, there is no CLKIN, just a SRCLK, but that is someting else!

There could be many reasons why this is not working. It's hard for me to debug your board without actually having it in hands. So just some ideas:

- Supply a clean differential REFCLK, I never tried one end tied to VDD/2

- Is /RESET high?

- Is BIAS at roughly 0.7V?

- Is A0-A3 different from 1111, which puts the chip in standby

- Did you double check your loop filter?

The easiest usually is to start from a running evaluation board, then compare all pins 1:1 with your board.

Stefan

Hello,

I am working on a custom PCB design with the DRS4 chip, and I can't get the PLL to lock.  I'm feeding CLKIN with a 1MHz CMOS clock (REFCLK- tied to VDD/2), and I'm using the same loop filter as the eval board.  I see from the datasheet that the PLL is enabled by default, so I'm not writing anything to the config register on startup.  I am just driving DENABLE high approx. 100ms after startup and looking for the PLL lock bit to go high.  When I look at DTAP, I see a 3MHz signal.  Can anyone tell me what I'm doing wrong?

-Tom

Just look at the definition of the function below, all parameters are explained there. In meantime we have a firmware fix to avoid the spikes inside the chip, but I have not yet found time to update the evaluation board.

Stefan

void DRSBoard::RemoveSymmetricSpikes(short **wf, int nwf,
                                     short diffThreshold, int spikeWidth,
                                     short maxPeakToPeak, short spikeVoltage,
                                     int nTimeRegionThreshold)
{
   // Remove a specific kind of spike on DRS4.
   // This spike has some features,
   //  - Common on all the channels on a chip
   //  - Constant heigh and width
   //  - Two spikes per channel
   //  - Symmetric to cell #0.
   //
   // This is not general purpose spike-removing function.
   // 
   // wf                   : Waveform data. cell#0 must be at bin0,
   //                        and number of bins must be kNumberOfBins.
   // nwf                  : Number of channels which "wf" holds.
   // diffThreshold        : Amplitude threshold to find peak
   // spikeWidth           : Width of spike
   // maxPeakToPeak        : When peak-to-peak is larger than this, the channel
   //                        is not used to find spikes.
   // spikeVoltage         : Amplitude of spikes. When it is 0, it is calculated in this function
   //                        from voltage difference from neighboring bins.
   // nTimeRegionThreshold : Requirement of number of time regions having spike at common position.
   //                        Total number of time regions is 2*"nwf".

Hi,

Is there a way that someone can help me and my student to enable RemoveSymmetricSpikes function in the drs_exam.cpp? We are not 100% sure how to call the function if you want to read out four waveforms.

Cheers,

Matthias

The chip itself can only sample a single waveform, that must be done in the attached software. The current DRSOscilloscope software coming with the evaluation board has not yet implemented that, but if you write your own software you can do so.

Dear all,

I have a question about the function that drs4 can perform.

Is there any function in drs4 that is analogous to that of "persistence display" in oscilloscope?? (accumulating pulses)

Thank you

Not github, but bitbucket: https://bitbucket.org/ritt/drs4eb/src/master/

But development kind of stalled, so there will be updates only in case of severe bugs, which are kind of gone after 10 years now.

Best,
Stefan

> Are there plans to add the drs software to github? (asking because I have users @ethz.ch that want to use it on debian,
> thus I'm creating official debian packages of it, if license allows so, but talking to upstream (the developers) would be
> much easier on github (or irc) than on this "DRS4 Discussion Forum".
> 
> Best,

Are there plans to add the drs software to github? (asking because I have users @ethz.ch that want to use it on debian,
thus I'm creating official debian packages of it, if license allows so, but talking to upstream (the developers) would be
much easier on github (or irc) than on this "DRS4 Discussion Forum".

Best,

Dear Stefan,

OK, it's good to hear! Thank you!

Best,
Seiya

This is a static shift register, so you can make the clock as slow as you want. Actually I don't use a "clock", I just use a data pin I control via a state machine in the VHDL code. This way I have more control over the edges. I need several (internal) clock cycles to produce one SRCLK clock cycle, but that does not matter for the DRS.

Stefan

Dear Stefan,

Thank you for your reply.
SRIN is directly connected to SROUT via FPGA for now, but it is unstable for the timing between clock and SRIN depending on the firmware logic.
We want to make our system more robust, so we are thinking to use a clock with a lower frequency (let's say 16.6 MHz) or change the duty cycle of a clock to keep more time between the rising edge and falling edge of a clock. This change is just for reading/writing the write shift register, we will use a 33 MHz clock for the analog readout in any case.
If we change like above, are there any concerns from the DRS4 side?

Best,
Seiya

Dear Seiya,

1) That's correct. SRIN is ampled at the falling edge. Pleae make sure to obey the hold-time as written in the datasheet. P.12, Fig. 11: SRIN must be stable before the falling edge of SRCLK and tH after the falling clock. tH is 5ns according to table 1. 

2) The write shift register is a 8-bit shift register, with an input, output and clock. After the first clock pulse, the 7th bit is shown, after the second clock pulse the 6th bit and so on. You you need 8 clock pulses to read the whole register. At the same time you write to the register, so what ever is present at SRIN will replace the old 8 bits of that register.

3) No this is not possible. When you read the register, you write to it at the same time. One possibilty is to connect SROUT to SRIN during that (maybe via the FPGA). Then you have a circular register wich is the same after each 8 clock pulses.

For your reference, I posted a commercial D-Flip Flop (TI SNHCS72). The DRS4 write shift register is a simple array of 8 such registers, with no CLR or PRE, where SROUT is Q of the last Flip Flop.

Best,
Stefan

Dear Stefan,

I have questions about the timing diagram of SROUT/SRIN signal to write/read a write shift register.
1) Value of SRIN signal is saved at the falling edge of SRCLK, correct? (It is written in datasheet, page12, "Bits are latched into the shift register on the falling edge of SRCLK")
2) When are 8-bits of write shift register shown through SROUT? At ridging edges of SRCLK? and with additional delay(~10ns)? or falling edges?
3) In my understanding, when SRCLK is sent to DRS4, we can read and write the values in parallel, right? If so, is it possible just to read the registers without updating the registers?

[Background]
We have two modes to set the write shift register, the first one is to always reconnect to the first line and another one is to reconnect to the same line as when DWRITE goes to Low.
We can read/write the write shift register with the first mode (channel reset, page1). But we rarely face the problem of write shift register, unexpected values are written, with the second mode. With this mode, SROUT signal is sent back to DRS from FPGA as SRIN to write the same value on the write shift register. So there is a small delay(~10ns) due to the routing (DRS->FPGA->DRS, page2). It seems SRIN signal is not stable around the falling edges of SRCLK, thus it could cause that unexpected values are written in write shifter register.
To understand the situation clearly, I'd like to know the answer to the above questions.

Thank you.

Best regards,
Seiya

I will try that, thanks!

The trigger is there only to trigger the chip, but cannot be used as a precise time reference. If you want to measure precise timing, do this always BETWEEN two inputs, never between an input and the trigger. You might want to split and delay your trigger signal and feed one copy to another input of the evaluation board as your reference.

Stefan

Dear all,

I had a question about timing jitter and external triggering.

I trigger the board externally with a 3V pulse from a DG645 delay generator and as a test I use the gated charge function to integrate another pulse of the DG which goes into channel 1 (the timing jitter between different outputs of the DG is on the order of ~25 picoseconds).

The issue I’m encountering is that the signal on channel 1 is jittering in time with ~1 ns, which means the signal is jittering with respect to my integration gate (point A and B). If I look at the data it always starts at t = 0.000 but my signal (pulse) moves around in time.

If I don’t use the external trigger but trigger on channel 1 directly the signal does not move with respect to the gate, but I can see the start and end of the trace move in time. If I look at the data the first data point is not at t = 0.000 but some other time, which jitters with ~1 ns.

I did repeat the voltage and timing calibration, but that did not help either.

Do you know where this jitter comes from and if I can get rid of it?

Best regards,

Elmer

If you have a board with cascading option, it should show the "combined" option in the 2048-bin option enabled (not grayed), as in the attached screen shot. If the 2048-bin option is all greyed out, the system does not recognize the cascading option. If your board has a sticker "2048 bin" and you still see the 2048-bin option greyed out, it might mean that a resistor on that board has been forgotten. If you do not see the "2048 bin" sticker on your board, you might not have a board with cascading option. So please check that. If the resistor is really missing, you can send us the board and we will add it.

Stefan