Bus Operations Tools

Bus operations work at the IEEE-488 protocol level — discovering devices, reading status, and issuing bus-level commands. These tools address the bus as a whole rather than individual instruments.

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bus_scan

Scan the GPIB bus for listening instruments. Sends ++findlstn to discover all devices, then optionally sends *IDN? to each discovered address to identify the instrument.

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge to scan
identify	boolean	No	Send *IDN? to each listener (default: true)

Example

result = await client.call_tool("bus_scan", {
    "bridge_name": "bench-a",
    "identify": True
})

Returns

Bus scan on bench-a: 3 listener(s)
  Address 5: Agilent Technologies E3631A (S/N: MY12345678)
  Address 7: Tektronix TDS2024B (S/N: C031234)
  Address 22: KEITHLEY INSTRUMENTS INC. MODEL 2000 (S/N: 1234567)

When identify is false, addresses are listed without identification:

Bus scan on bench-a: 3 listener(s)
  Address 5: listener found
  Address 7: listener found
  Address 22: listener found

Tip

Set identify=false for a faster scan when you only need to know which addresses are active. Identification adds one *IDN? query per listener, each with a full read timeout cycle.

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serial_poll

Serial poll one or all instruments on the bus. Returns the status byte for each polled instrument. Bit 6 (0x40) indicates the device is requesting service (RQS/SRQ).

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge
address	integer	No	GPIB address to poll (0—30). If omitted, polls all known listeners

Example

# Poll a single instrument
result = await client.call_tool("serial_poll", {
    "bridge_name": "bench-a",
    "address": 22
})

# Poll all known listeners
result = await client.call_tool("serial_poll", {
    "bridge_name": "bench-a"
})

Returns

Serial poll on bench-a:
  Address 22: status=0x40 (64) [SRQ]
  Address 5: status=0x00 (0)

Note

When polling all instruments (no address parameter), the tool uses ++allspoll with the addresses from the most recent bus_scan. Run bus_scan first if the bus has not been scanned yet.

Status byte bit assignments (IEEE 488.2):

Bit	Mask	Meaning
6	0x40	RQS — device is requesting service
5	0x20	ESB — event status bit (check *ESR?)
4	0x10	MAV — message available in output queue
0—3, 7	varies	Instrument-specific

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check_srq

Check if the SRQ (Service Request) line is asserted on the bus. If SRQ is asserted, the tool automatically calls ++findrqs to identify which device is requesting service.

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge to check

Example

result = await client.call_tool("check_srq", {
    "bridge_name": "bench-a"
})

Returns

When a device is requesting service:

SRQ ASSERTED on bench-a — device at address 22 requesting service (status=0x50)

When no device is requesting service:

SRQ not asserted on bench-a

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bus_clear

Send a device clear command. With an address, sends Selected Device Clear (SDC) to that specific instrument. Without an address, sends Universal Device Clear (DCL) to all devices on the bus.

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge
address	integer	No	GPIB address (0—30) for selective clear. Omit for universal clear

Example

# Clear a specific instrument
result = await client.call_tool("bus_clear", {
    "bridge_name": "bench-a",
    "address": 22
})

# Clear all instruments
result = await client.call_tool("bus_clear", {
    "bridge_name": "bench-a"
})

Returns

Sent Selected Device Clear to address 22 on bench-a

or

Sent Universal Device Clear on bench-a

---

bus_trigger

Send Group Execute Trigger (GET) to instruments. Triggers cause instruments to initiate a pre-configured action, typically a measurement.

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge
addresses	array of integers	No	GPIB addresses to trigger. If omitted, triggers the currently addressed device

Example

# Trigger specific instruments
result = await client.call_tool("bus_trigger", {
    "bridge_name": "bench-a",
    "addresses": [5, 22]
})

# Trigger the currently addressed device
result = await client.call_tool("bus_trigger", {
    "bridge_name": "bench-a"
})

Returns

Triggered addresses [5, 22] on bench-a

---

interface_clear

Assert Interface Clear (IFC) for 150 microseconds. This resets all bus interfaces to their idle state and establishes this bridge as Controller-In-Charge (CIC).

Multi-controller warning

If another controller is on the bus, asserting IFC overrides it. Only one device can be Controller-In-Charge at a time. Use this tool to take control of the bus or to recover from a hung state, but be aware of the implications in multi-controller setups.

Parameters

Name	Type	Required	Description
bridge_name	string	Yes	Name of the bridge

Example

result = await client.call_tool("interface_clear", {
    "bridge_name": "bench-a"
})

Returns

IFC asserted on bench-a — this bridge is now Controller-In-Charge