Difference: RichFEEandDAQUpgrade (1 vs. 3)

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22 Dec 2008 - Main.MichaelBoehmer
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META TOPICPARENT name="DaqUpgradeOverview"
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First light smile

Despite the fact the the description below is really outdated, I can pronounce the first really important step from connecting the new RICH ADCM to the TRBnet, and getting it working with the new APV-FE.

triggered.pdf

One ADCM (version 0) is connected to one APV-FE via a first version of backplane; connection to the TRB is made by TRBnet fibre.

Access is done by slow control channel, with help of Jan Michael's TrbRegIO entity and the new written bus_handler from me.

The entities taking care of the APV data handling were taken from the first GTB based development and connected nearly 1:1 to the new TRBnet slow control access.

Triggering was achieved by simple TRBnet register access.

The attached PDF shows (in the lower part) the data sent from the APV module (analog measurement). This differential signal passes an input stage, enters the ADC and is digitized by 40MHz @ 12bit. ADC data is sent at 480MHz serially (240MHz DDR data encoding) to the FPGA, is being deserialized and put into different entities which data care about data separation. The result is sent as 12bit data to a logic analyzer debug port and shown as "analog" representation in the upper part of the PDF page.

As you can see, digital reconstructed data is the same as the analog input data smile
 

Analog Frontend (AFE)

(pictures to be inserted soon)
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  To recognize this data frame one needs to sample the APV25 output lines with an ADC at 40MHz, phase shifted in a way to compensate cable delays.

-- MichaelBoehmer - 20 Mar 2007
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META FILEATTACHMENT attr="h" comment="complete data chain successfully done" date="1229964713" name="triggered.pdf" path="triggered.pdf" size="85524" user="MichaelBoehmer" version="1.1"
Revision 2
21 Mar 2007 - Main.MichaelBoehmer
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META TOPICPARENT name="DaqUpgradeOverview"

Analog Frontend (AFE)

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The choice of connection to TRBs (optical / LVDS) has to be based on the expected data rates during experiment, as well as on the need of additional connections (like a central clock / trigger).
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Data rate estimation

For selecting a suitable media as connection between the LM and the TRB addon, we must consider one "worst case" scenario. If we take one BP with five AFEs, we have 5*64 analogue channels. We can assume 5% occupancy in the detector, and we will take three samples of the detector signal to be able to distinguish photons from noise, and to do some baseline restauration.

As raw data per channel we will have three data words of 32bit, which should be compressed to one 32bit word after processing in the LM.

Assuming a trigger rate of 20kHz and a header of 32bit, we will end up with a data volume of (320 * 0.05 * 4byte + 4byte) * 20kHz = 1.3MB/s per BP. For the whole RICH this number must be multiplied by 16 BP and by 6 sectors, ending up with a total amount of RICH data of approx. 128MB/s.

In case of pedestal making this number will increase, as all channels need to be readout, and 20kHz won't work anymore if we want to do pedestal creation in the event builder:

(320 channel * 1.00 * 4byte + 4byte) * 20kHz = 24.5MB/s per BP

(16 BP * 6 sectors * 24.5MB/s = 2.3GB/s (whole RICH)

Pedestal calculation could be implemented in the TRB DSP?
 

APV25S1 - basics of operation

The APV25S1 preamp ASIC was designed for the CMS experiment. It has been used mainly for silicon readout, but recently also to upgrade the COMPASS RICH from GASSIPLEX readout. From our first experiences it seems feasable to get the HADES RICH also working with the APV25S1, giving us more possibilities than the current GASSIPLEX based readout.
 
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