Channel map

The channels in LArSoft are not the same as those numbered by the DAQ. Maps to convert between the two can be downloaded from this page.

The DAQ reads out the data from 16 RCEs (Reconfigurable Cluster Elements), each of which reads out 128 channels. The position of the RCE and the channel number read out by each uniquely define the online channel. The offline channel is defined within LArSoft (see Dump the wire geometry to a text file).

The positions of the RCEs on the APAs are shown in an attached figure (note in this figure the APA numbering is consistent with the LArSoft geometry (and not necessarily any online convention)). RCE 0 reads out channels 0-127, RCE 1 channels 128-255 etc.

There are two channel maps attached (text files). One is a simple one to one mapping (channelMap.txt), with the first column representing online (DAQ) channel and the second offline channel. There is also a more detailed map (detailedMap.txt), with information such as plane, TPC, RCE number and RCE channel included. Any requests for more useful information to be included can be sent to Mike Wallbank ().

Disclaimer: the map may change (if hardware components are rewired, for example)! Any changes will be included in future versions of the map...

Mike's notes (mainly for myself, because I keep forgetting everything I work out!)

Don't believe the lies, there is a difference between 'A' and 'B' sides in Dan's maps! Well, not really... But if using the version of the map with coordinates, there is (because different sides have different x values). The correct order is: A-short drift; B-long drift.
More lies, there is a correct left and right! Defined as if looking from the long drift volume at the APAs.
As of v4, collection wires in the short drift volume have been swapped (A side). In the unordered map (not on the web page, this is just for my benefit!), this has been implemented by reversing the offline numbers (because these are sequential so easier) for both drift volumes. The reasons both are reversed is historical, because when I previously reversed them for the long drift region, I reversed the channels in the online. So actually only the short drift volume wires are reverse wrt to the offline.

Channel map service

There is a channel mapping art service in lbne-raw-data which can be used both online (in lbne-artdaq) and offline (in larsoft). The service provides method to obtain online and offline channel numbers from their equivalent channels, and for obtaining further information such as RCE, plane and APA number. It will always use the most recent version of the map and so should be used when needing a reliable interface to the channel map.

Instructions for how to use it are as follows:

You need to compile with the library
in your CMakeLists.

fhicl configuration
#include “service_dune.fcl"
It is configured correctly in this file.

#include “lbne-raw-data/Services/ChannelMap/ChannelMapService.h”

Use in code
art::ServiceHandle<lbne::ChannelMapService> channelMap;
channelMap->Online(offlineChannel) // to get online from offline
channelMap->Offline(onlineChannel) // to get offline from online

Map history

v0: Initial channel map
v1: Fixed issue with the positioning of the RCEs on each APA -- was reverse in the online and offline.
v2: Fixed issue with Dan's online channel map. Collection wires were listed in reverse order on the 'B' side (long drift volume side).
v3: Fixed issue with collection wires: it appeared from looking at muon tracks that odd and even numbered channels were reversed.
v4. Complete rewrite of the map. RCE order is now well defined (see image attached). The collection wire reversing and alternative
collection channel swapping has been applied as in previous versions.
v5: Another complete rewrite. Realised Dan's maps are wholly incorrect and so ignoring them. Now just using the connections on
the APAs, so should be much more robust (see attached figure). Hopefully the final version.
v6: Updated to use v6 of the LArSoft geometry