stm32_link: sync iin_avg_ma comment with live firmware protocol

Firmware now runs BOTH iin limits (IIN_MAX reverse-feed and the IIN_MIN
forward OCP, raised to -47A) on the 8-sample boxcar; wire format is
unchanged (verified field-by-field against the live code64 console,
including a synthetic-frame decode). Note the field is a raw int16 mA
cast and wraps at +-32.768A (observed +26.5A at a true -39.0A) -- the
float iin field is the honest monitor above that.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -115,7 +115,17 @@ The GUI provides:
   protection shut the output down), the sweep aborts immediately, reports
   which protection fired (OVP / OV / OC / OP / OT), and saves the points
   collected so far instead of logging garbage rows for the rest of the
-  grid.
+  grid. A converter-output collapse (load voltage below half the expected
+  Vout while the supply is still up -- the DUT shut itself down) aborts
+  the same way; when the STM32 link is up the abort message names the
+  firmware limit/fault bits from the last frame before the brownout
+  blackout.
+- Sweep finish estimate: the status line shows `ETA hh:mm (N pts, ~M min
+  left)` next to each measured point. The remaining grid is deterministic
+  (the steps that pass the feasibility gate), but the cost per point is
+  not (settle time + instrument round-trips that vary per setup), so the
+  per-point time is measured as a running average -- thermal-hold pauses
+  excluded -- and extrapolated over the remaining feasible points.
 - Load range pinning: a mid-sweep auto-range transition on the Prodigit
   momentarily unloads the converter, so at sweep start the CC range is
   pinned to Range II for the whole run (auto-ranging restored after, with

testbench/gui.py

@@ -29,6 +29,7 @@ from testbench.bench import MPPTTestbench
 from testbench.gui_workers import InstrumentWorker, Cmd, STM32Worker
 from testbench.stm32_link import (
     FLAG_NAMES, FLAG_INFO_MASK, build_ping, build_clear_flags,
+    flags_to_names,
 )
 
 
@@ -1746,6 +1747,25 @@ class TestbenchGUI(tk.Tk):
             return None
         return b.etemp, b.btemp
 
+    def _stm32_fault_note(self) -> str:
+        """Last STM32 fault flags as a console suffix, '' when unlinked.
+
+        On a converter collapse the MCU (fed from the Vout rail) browns
+        out, so the LAST frame before the blackout usually carries the
+        limit/fault bit that fired -- report it even when stale.
+        """
+        w = self.stm32
+        if not w:
+            return ""
+        b, wall = w.get_latest()
+        if b is None:
+            return ""
+        names = flags_to_names(b.status_flags & ~FLAG_INFO_MASK)
+        txt = ", ".join(names) if names else "no fault bits"
+        age = time.time() - wall
+        stale = f", {age:.0f}s stale" if age > TELEM_STALE_S else ""
+        return f" [STM32: {txt}{stale}]"
+
     @staticmethod
     def _supply_trip_cause(bench) -> str:
         """Best-effort query of which supply protection fired."""
@@ -1911,6 +1931,43 @@ class TestbenchGUI(tk.Tk):
             self._console(f"Load range readback failed ({e}) - range check "
                           f"skipped", "warn")
 
+        # Finish-time prediction.  The grid is deterministic (steps that
+        # pass the feasibility gate), but the cost per point is NOT: it is
+        # settle (known) + instrument round-trips (HIOKI auto-range wait +
+        # VISA latency, varies per instrument setup) + occasional holds.
+        # So the per-point time is MEASURED as a running average and
+        # extrapolated over the remaining feasible grid points.
+        def _in_range(x, stop_, step_):
+            return (x <= stop_ + step_ / 2 if step_ > 0
+                    else x >= stop_ + step_ / 2)
+
+        def _gate_ok(ll_, v_):
+            # mirror of the in-loop rejection gate (reads the live
+            # vout_est / range_max / psu_imax)
+            if range_max is not None and ll_ > range_max * 1.001:
+                return False
+            return _est_input_current(load_mode, ll_, v_, vout_est) <= psu_imax
+
+        def _pts_remaining(v_now, ll_next):
+            """Feasible grid points from (v_now, ll_next) to the end."""
+            if v_step == 0 or l_step == 0:
+                return 0
+            cnt = 0
+            vv, ll_ = v_now, ll_next
+            while _in_range(vv, v_stop, v_step):
+                while _in_range(ll_, l_stop, l_step):
+                    if _gate_ok(ll_, vv):
+                        cnt += 1
+                    ll_ += l_step
+                vv += v_step
+                ll_ = l_start
+            return cnt
+
+        self._console(
+            f"Sweep grid: {_pts_remaining(v_start, l_start)} feasible "
+            f"point(s) planned - finish estimate appears after the first "
+            f"point")
+
         bench.supply.set_current(current_limit)
         bench.supply.output_on()
         bench._apply_load_value(load_mode, l_start)
@@ -1920,6 +1977,8 @@ class TestbenchGUI(tk.Tk):
         n = 0
         v = v_start
         applied = l_start   # last load setpoint actually commanded
+        t_pt = None                  # running avg seconds per accepted point
+        t_last = time.monotonic()
 
         try:
             while not stop.is_set():
@@ -1960,9 +2019,11 @@ class TestbenchGUI(tk.Tk):
                         continue
 
                     # Pause near the firmware thermal trips (holds at ~1 A)
+                    t0_hold = time.monotonic()
                     held = self._thermal_hold(bench, load_mode, vout_est, stop)
                     if held is not None:
                         applied = held
+                        t_last += time.monotonic() - t0_hold  # ETA: skip hold
                         if stop.is_set():
                             break
 
@@ -1990,6 +2051,23 @@ class TestbenchGUI(tk.Tk):
                             f"{n} collected point(s)", "error")
                         stop.set()
                         break
+                    # Converter-output collapse abort: the DUT shut itself
+                    # down (firmware limit / fault) while the supply stayed
+                    # up -- the supply-side check above never sees this
+                    # (run 2026-07-07: Vout 48->3V at Vin=55V and the sweep
+                    # kept stepping the rest of the grid).
+                    if point.load_voltage < vout_est * 0.5:
+                        results.pop()   # this point is garbage
+                        n -= 1
+                        self._console(
+                            f"Converter output collapsed at V={v:g}V "
+                            f"{load_mode}={ll:g}{unit}: Vout "
+                            f"{point.load_voltage:.1f}V, expected ~"
+                            f"{vout_est:.0f}V{self._stm32_fault_note()} - "
+                            f"aborting sweep, saving {n} collected "
+                            f"point(s)", "error")
+                        stop.set()
+                        break
                     if point.load_voltage > 5.0:
                         vout_est = point.load_voltage
                     # Measured backstop: the estimate can be off (eff, Vout)
@@ -2011,6 +2089,17 @@ class TestbenchGUI(tk.Tk):
                         ll += l_step
                         continue
 
+                    # Update the finish-time estimate from this point's
+                    # measured wall time (thermal holds already excluded)
+                    now_m = time.monotonic()
+                    dt_pt = now_m - t_last
+                    t_last = now_m
+                    t_pt = (dt_pt if t_pt is None
+                            else 0.7 * t_pt + 0.3 * dt_pt)
+                    rem = _pts_remaining(v, ll + l_step)
+                    eta = time.strftime(
+                        "%H:%M", time.localtime(time.time() + rem * t_pt))
+
                     # Push data for live graph/readout updates
                     gui_data = {
                         "supply_V": point.supply_voltage,
@@ -2040,11 +2129,14 @@ class TestbenchGUI(tk.Tk):
                             pass
                         self._sweep_data_queue.put_nowait(gui_data)
 
+                    mins = rem * t_pt / 60.0
                     self.after(
                         0,
-                        lambda v=v, ll=ll, pt=point, n=n: self._svi_status.config(
+                        lambda v=v, ll=ll, pt=point, n=n, eta=eta, rem=rem,
+                               mins=mins: self._svi_status.config(
                             text=f"[{n}] V={v:.1f}V {load_mode}={ll:.1f}{unit} "
-                                 f"EFF={pt.efficiency:.1f}%"
+                                 f"EFF={pt.efficiency:.1f}%  ETA {eta} "
+                                 f"({rem} pts, ~{mins:.0f} min left)"
                         ),
                     )
 

testbench/stm32_link.py

@@ -164,7 +164,7 @@ class BroadcastData:
     param_value: int = 0   # raw bits; interpret via decode_param_bits(param_type, ...)
     pong: int = 0          # increments when the MCU processes CMD_PING
     sys_current_ma: int = 0   # Vout-rail housekeeping current, mA
-    iin_avg_ma: int = 0       # 8-sample boxcar of iin, mA (the IIN_MAX trip quantity)
+    iin_avg_ma: int = 0       # 8-sample boxcar of iin, mA (the IIN_MAX/IIN_MIN trip quantity)
     timestamp: float = field(default_factory=time.time)
 
     @property