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GMB Instructions

What the GMB does

In the IFR, we use several types of the General Monitoring Board (aka GMB) to monitor ambient data:
  • RPC dark currents
  • temperatures
  • low voltage for FEC power.
A few properties of the GMB:
  • The GMBs are located physically in special crates, that they share with the multiplexes of the single rate counting system.
  • The GMBs are connected to the IFR detector control system through a CANBUS. The CAN bus is driven by a CAN controller located in the VME crate of the IFR IOC.
  • The IFR detector control system has 4 CAN buses:
    1. CAN0: barrel
    2. CAN1: barrel
    3. CAN4: forward endcap
    4. CAN6: backward endcap
  • The GMB is identified on the bus by a HARDWARE ADDRESS that is WRITTEN ON THE BOARD. This is very important! The position of the GMB in a crate doesn't play any role. That means that when you replace a defective GMB, you need to make sure that the new one has the same hardware address written on it.
  • To write a hardware address on a GMB, you need a PC with a PC CAN controller and a special software. Ask one of the following people (in this order):
    1. Ray Rodriguez
    2. Mark Freytag
    3. Dave Nelson
    Thy all have the necessary hardware and software.
  • The GMBs are connected to the CAN bus in a daisy chain. The CAN bus needs to be terminated at the last one.
  • The GMB has 4 LEDs on it, that each indicate something (picture coming):
    1. 2 green LEDs telling you the GMB is powered
    2. a third green LED telling you it sees the CAN bus.
    3. a yellow LED that goes on every time the GMB is read out.
    4. a red flashing LED that tells you it sees the bus clock. It is very hard to see.

Debugging GMB problems

Symptoms:
  • Values are not being updated, and the freshness number isn't changing.
  • It is white in EPICS (lost contact with it).
  • It is being updated but all (or a group of) channels of a GMB read the same value.
What you need to find out:
  • Does the bus see the GMB? Use xyplex and scan the bus:
    [bbr-dev23] ~ > xyplex -f ifr-mon
    Trying 134.79.158.11...
    Connected to bbr-tty1.SLAC.Stanford.EDU.
    Escape character is '^]'.
    
    ifr-mon~> canScan "CAN0"
     BaBar Modules found:
        Station, Board Serial Number, Software Version: 1 29, 302
        Station, Board Serial Number, Software Version: 2 37, 302
        Station, Board Serial Number, Software Version: 3 33, 302
        Station, Board Serial Number, Software Version: a 2c, 302
        Station, Board Serial Number, Software Version: b 35, 302
        Station, Board Serial Number, Software Version: c 3a, 302
        Station, Board Serial Number, Software Version: d 24, 302
        Station, Board Serial Number, Software Version: e 10, 302
        Station, Board Serial Number, Software Version: 10 b, 302
        Station, Board Serial Number, Software Version: 11 4f, 302
    
     Wiener crates found:
        Status of crate 7b: ff
        Status of crate 7c: ff
    value = 0 = 0x0
    ifr-mon~> 
    
    If the GMB is not appearing there:
    1. power cycle the bus (LV-mon switches in electronics house)
    2. is there a GMB that should not be there in the upper list? If so, somebody may have replaced a GMB
    3. go to IR-2 and look at the board: bad contact?