IBLN(3)

📦
version 4.3.7 · 2 versions
, in ubuntu stonking

💖 IBLN(3) — the "is anybody home??" check 💖

okay bestie, pull up a chair, because this one lives in the Traditional API Functions corner of the linux-gpib universe and it is so useful. It's ibln(3) and its whole job is vibes-checking the bus. 🦋

🌸 NAME 🌸

ibln — check if listener is present (board or device)

Like, is there actually a device there, or are we yelling into the void? That's the question. 👑

✨ SYNOPSIS ✨

#include <gpib/ib.h>

int ibln(int ud, int pad, int sad, short *found_listener);

🎀 DESCRIPTION 🎀

So ibln() checks for the presence of a device, and it does it by attempting to address it as a listener. Cute, right? It just... says hi to it on the bus and sees if anyone answers. 🙈

Here's the cast of characters:

  • ud — specifies the GPIB interface board which should check for listeners. Main character board energy. But wait, plot twist: if ud is a device descriptor, then the device's access board is used instead. Slay, the descriptor knows its own board. 💅
  • pad — the GPIB address to check is specified by pad and sad, bestie. pad specifies the primary address, and the valid values are 0 through 30. That's the whole range. Don't try to be extra.
  • sad — gives the secondary address, and it may be a value from 0x60 through 0x7f (that's 96 through 127 for the decimal girlies 🧮), or one of the constants NO_SAD or ALL_SAD. And what do those mean?
    • NO_SAD indicates that no secondary addressing is to be used.
    • ALL_SAD indicates that all secondary addresses should be checked. (yes, every single one, go off ✨)

Now, the verdict:

  • If the board finds a listener at the specified GPIB address(es), then the variable specified by the pointer found_listener is set to a nonzero value. 🎉
  • If no listener is found, the variable is set to zero. 💀 (rip, nobody's home)
⚠️ important caveats, no cap: the board must be controller-in-charge to perform this function. Also, it must have the capability to monitor the NDAC bus line (see iblines()). If it can't do that, this whole thing isn't gonna work.

🫶 the messy extra-effect tea 🫶

This function has the additional effect of addressing the board as talker for the duration of the Find Listeners protocol, which is — and I quote — beyond what IEEE 488.2 specifies. So it's lowkey doing a little extra.

Why, you ask? Because some boards cannot reliably read the state of the NDAC bus line unless they are the talker. Being the talker causes the board's gpib transceiver to configure NDAC as an input, so its state can be reliably read from the bus through the transceiver. It's giving "I had to become the main character just to read one (1) bus line." 😭

🌈 RETURN VALUE 🌈

The value of ibsta is returned. That's it, that's the return value. Short, sweet, iconic. ⭐

Copyright © 2003-2006, 2008 Frank Mori Hess

and that's the whole page, bestie!! thanks for reading, mwah 🫶 the source on this one is linux-gpib 4.3.7 and it's dated 07/06/2026 — so basically fresh out the oven ✨💖 go forth and check your listeners, you absolute legend 🌸🎀

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