---
id: pod-hardware
title: "Pod Hardware — the fixed target (7 monitors, D3D9, RIO)"
status: established
source_sections: "PROGRESS_LOG.md §3; the PLATFORM PROFILE + GAUGE DEV-COMPOSITE notes"
related_topics: [gauges-hud, rendering, project-overview]
key_terms: [pod, RIO, MFD, IG-board, SVGA16]
---

# Pod Hardware (the fixed target)

The port must run on (a) a dev box and (b) the fixed arcade pod. The pod is a hard constraint that
bounds the graphics API. Full detail: `docs/PROGRESS_LOG.md §3`.

## Displays
- **2 video cards → 7 monitors:** main 3D view **800×600**; radar **640×480**; five monochrome MFDs
  driven as one **1280×480** horizontally-spanned surface. [T1]
- Requires **old NVIDIA drivers** for the MFD horizontal spanning — a hard constraint that bounds
  the graphics API → **Target Direct3D 9** (lowest common denominator that runs on old-driver pods
  AND modern cards; one codepath). NOT Vulkan/D3D11+. CUDA is irrelevant (compute, not display). [T1]

## Cockpit I/O (RIO)
Joystick X/Y, throttle, pedals, buttons over **serial COM** (`L4RIO`, `L4SERIAL`). Must be remapped
to keyboard/gamepad on a dev box; real wiring is a pod bring-up task (Phase 8). The engine is a PUSH
model — `LBE4ControlsManager` groups are fed by all devices (RIO on the pod, DirectInput on dev);
the `MechControlsMapper` interprets them ([[locomotion]]). [T2]

### The button space + lamps [T0, L4CTRL.h enum]
buttonGroup addresses 0x00-0x47: `AuxLowerRight/Left 1-8` (0x00-0x0F), `Secondary1-12` (0x10-0x1B),
`AuxUpperCenter/Left/Right 1-8` (0x20-0x37 — the preset/eng "display eng data" banks; **0x30-0x37 =
the target HOTBOX**, pilot select), icom/door 0x39-0x3C, `Panic` 0x3D (the config-mode lamp),
`Throttle1` 0x3F (throttle-head = REVERSE THRUST), joystick cluster 0x40-0x47 (Main trigger 0x40,
hat 0x41-0x44, Pinky/ThumbLow/ThumbHigh 0x45-0x47 — the four MAPPABLE fire buttons). "Lamp buttons"
are literal: physical illuminated pushbuttons in panels around the screens; the RIO `LampRequest`
protocol lights them (`MakeLinkedLamp`), reports burned-out bulbs (`RIODeadLamps` failure page,
per-lamp names). A lit button = active. Keypads are NOT buttons: `keyboardGroup[KeyboardPilot/
KeyboardExternal]` carry key VALUES ('0'-'9','A'-'F', L4CTRL.cpp:2526). RIO event convention:
press = `buttonGroup[a].Update(a+1, modeMask)` (mask saved), release = `Update(-a-1, savedMask)`
(L4CTRL.cpp:2470-2520).

### Desktop input remap — CONTROLS.MAP + XInput (2026-07-18) [T2 live]
`game/reconstructed/btinput.cpp` + `content/CONTROLS.MAP` (WASD-classic default, compiled-in twin;
`content/CONTROLS_NUMPAD.MAP` = the corrected community numpad profile). Grammar: `key <name>
button <addr>|axis <axis> deflect|rate <n>|keypad pilot|external <0-15>|pckey <char>|action
<name>`; `pad <button>` same targets; `padaxis <src> axis ... [invert] [deadzone d] [rate n]`.
Axes: Throttle (lever, rate-walks + sticks), LeftPedal/RightPedal/Pedals (turn, springs),
JoystickX (torso twist), **JoystickY (torso ELEVATION — pitch aim; every 1995 control mode
routes it to Torso::SetAnalogElevationAxis; keys R/F + pad LeftStickY in the default map;
verified to the authentic VerticalLimitTop clamp, 20° on the Blackhawk; aims the GUNS — reads
on the HUD elevation tape, the eyepoint stays level)**. Emissions mirror the RIO conventions above exactly; the four fire
buttons (0x40/45/46/47) publish as levels to the bring-up fire channels instead of buttonGroup
(avoids double-fire once the streamed ChooseButton mappings are exercised). XInput loads
dynamically (xinput1_4 → 9_1_0; disconnected-pad probing rate-limited to 1 Hz). **Keys claimed by
a binding are SUPPRESSED from the legacy WM_CHAR/KEYUP feed** (`BTInputSuppressKey`, hook at
L4CTRL.cpp keyboard read) — this ended the historic DOUBLE-DISPATCH: 'w' drove AND selected pilot
0; F5's key-up value 0x74 aliased to the 't' hotkey; letter key-ups (uppercase) fed the developer
fake-event dispatcher. Unbound keys keep their authentic 1995 dispatcher meaning (reachable from
any key via `pckey`). The old dual-use 'V' (view toggle + look-behind) is split: V = ViewToggle,
B = LookBehind. Verified live: bindings load, W/NumPad8 drive (spd rises), X all-stop, aux-button
emission ([input] 0x2f PRESS), suppression both directions ('r' delivered / 'w' swallowed),
full-keyspace WM_CHAR+WM_KEYUP fuzz survived. Diag: `BT_INPUT_LOG`.

### The pod throttle is ANALOG-CONTINUOUS, not notched (verified end-to-end) [T1]
The authentic pod throttle path — traced 2026-07 (task #50 throttle-fidelity question):
1. **Hardware → RIO:** serial `AnalogReply` packet → `Ranger("Throttle", 0, 800, .05)` — raw counts
   0–800, 5% deadband, auto-ranging offset, output a CONTINUOUS Scalar; the sign is inverted
   ("Throttle counts BACKWARDS", `engine/MUNGA_L4/L4RIO.cpp:1374-1377`, Ranger @L4RIO.cpp:461-701).
   No quantization/notching anywhere in `Ranger::Update`.
2. **Manager:** `LBE4ControlsManager::Execute` → `scalarGroup[ScalarThrottle].Update(&rioPointer->
   Throttle, mode_mask)` on every AnalogReply (`L4CTRL.cpp:1379-1382`). ScalarThrottle = index 0 →
   manager+0x24 (scalarGroup base 0x24, 0x20/entry; buttonGroup base 0x1c0, keyboardGroup 0x160).
3. **Streamed `.CTL` mapping (the "handled elsewhere"):** `MechRIOMapper`'s ctor @004d266c binds NO
   throttle — the bind comes from the type-19 `ControlMappingStream` resource named **"L4"** (child
   of the per-mech type-6 `ControlMappingsList`; installed by `BTL4APP MakeViewpointEntity` via
   `CreateStreamedMappings` @0047703c). BTL4.RES "L4" record [1]:
   `Scalar Throttle → subsystemID 0 (ControlsMapper slot), DirectMapping, attr 4, mask 0xffffffff`.
   Attr 4 = "ThrottlePosition" @ mapper+0x11c (binary IndexEntry table @0050efd8: id 4 → offset
   0x11d-1 = 0x11c, name "ThrottlePosition" @0050f28f). Reverse = record [2]: `Button Throttle1
   (0x3F, on the throttle handle) → attr 6 ReverseThrust@0x124`. Turn = pedals value-bound in the
   ctor (manager+0x44/+0x64 → mapper+0x1b4/+0x1b8).
4. **Interpretation:** `L4MechControlsMapper::InterpretControls` @004d196c applies the ONLY software
   detent — snap to 1.0 when |t−1.0| ≤ 0.05 — then `MechControlsMapper::InterpretControls` @004afd10
   computes `speedDemand@0x128 = maxSpeed(mech+0x34c) × throttlePosition(0x11c) × scale(mech+0x5c0)`
   (forward) or `−maxSpeed × throttlePosition` (reverse flag 0x124).

**Consequence:** the original pod produced a continuously varying speedDemand while the lever moved
(updated per serial AnalogReply, NOT per render frame). There are NO "5 throttle notches" anywhere
in the software path. (Keyboard keys '1'-'5' in @004d1bf0 set controls-manager MODE masks; the
'+'/'-' pair steps a [0,5] value that drives `pow(2,x)` into mech+0x404 = HUD zoom 1×–32× — neither
is a speed setting.) The mech's `throttleState@0x4a4` writer remains un-exported (likely in the
0x4a9b5a–0x4ab188 gap) — [[open-questions]].

**MECHANICAL-notch hypothesis (2026-07-16) [T4, hardware]:** the "5 speeds" pod lore may still be
true — as detents in the throttle QUADRANT hardware, invisible to the software (the pot reads
continuous counts regardless of where the lever mechanically rests). Independent corroboration
from the gait math ([[locomotion]]): the gait SM has NO stable state for a demand between the walk
cap (`walkStrideLength`@0x534) and the run engage speed (`reverseSpeedMax`@0x538, the walk→run
transition clip's exit speed) — a demand PARKED in that band hunts walk→shift-up→shift-down
forever, firing the authored EngineShiftFwd/Rev sounds each swing (binary-verified, all-authentic
data: Blackhawk band = demand 22.02–30.87 = throttle 36–50%). A design like that only ships if the
hardware discourages parking in the band. Port accommodation: the keyboard lever snaps out of the
dead band AT REST (`mech4.cpp` "GAIT DETENT"; sweeping through while held stays continuous =
authentic moving lever). Ask Nick: did the pod throttle quadrant have mechanical detents
(how many / positions)? — [[open-questions]].

## Multi-surface gauge path (intact, pod-only by default)
The pod multi-surface path EXISTS and is intact: `DPLRenderer::FindBestAdapterIndices` (multi-
adapter selector, honors PRIMGAUGE/SECGAUGE/MFDGAUGE/SPANDISABLE), `SVGA16::BuildWindows` (a
fullscreen D3D device + window per gauge/MFD surface, MFD span = width×2), `L4GaugeRenderer` (gated
on `L4GAUGE`). `content/SETENV.BAT` is the authentic pod env preset (L4CONTROLS=RIO,KEYBOARD;
L4GAUGE=640x480x16; L4PLASMA=com2). [T2]

## Platform profile switch
`-platform pod|dev` (or `BT_PLATFORM` env; default DEV) selects a runtime env preset WITHOUT forking
the codepath. **DEV** = keyboard + single 800×600 window. **POD** = RIO input (keyboard fallback off
serial) + multi-surface gauges (from SETENV.BAT/L4GAUGE on real hardware). `-platform pod` does NOT
auto-enable L4GAUGE (each surface needs its own fullscreen device on the pod's 2 cards). Off-pod, the
6 MFD surfaces render in a dev window via `BT_DEV_GAUGES` ([[gauges-hud]]). [T2]

## MFD surface model
All cockpit surfaces are bit-plane MASKS over ONE shared `SVGA16` pixelBuffer: `sec`=palette low
byte; `Heat`=0x4000, `Mfd2`=0x0400, `Comm`=0x8000, `Mfd1`=0x0100, `Mfd3`=0x1000; `Eng1-3` =
engineering-mode alt planes; `overlay`=0x00C0 (shares the sec surface). See [[gauges-hud]]. [T2]

## The 1995 player manual — alignment audit (2026-07-18) [T1, primary source]
`reference/manual/Tesla40_BT_manual.pdf` (34pp, from Nick). CONFIRMS the reconstruction on
every checked control behavior:
- **Control modes are named BAS / MID / ADV** (basic/middle/advanced; our Basic/Standard/Veteran
  names came from the RP analog — mechanics identical): BAS = joystick turns the mech, pedals
  inactive, NO torso twist; MID = pedals turn + auto-slow for tightest radius, joystick = torso;
  ADV = as MID but NO auto-slow (wider radius at speed) — exactly our mapper's turn-clamp
  difference. Mode button = top right of the secondary screen.
- **Stick right = torso right** in MID/ADV (p8) — the corrected sign. **Blackhawk and Owens are
  the fixed-torso exceptions** (named in print!); twist arc "about 120°" (per-mech: Loki/Thor
  tables say Torso Limit 110°, Torso speed 60°/s).
- **Throttle is a continuous lever** (push=accelerate, pull=stop; inertia); **reverse = HOLD the
  red throttle button** (release = forward) — our 0x3F hold-state model.
- **Hot Box Selector MFD** = callsign buttons + a **CLOSEST** button (lower right = our hotbox
  button 8 → ChooseNearestPilot); radar = travel-oriented, 60° vision wedge sweeps with twist,
  red hot box + callsign on contacts; **map zoom ± buttons** flank the secondary screen.
- **Experience gates the hunting aids**: viewscreen hot box + hunting-guide arrow appear in
  STANDARD sim mode only (not veteran/expert); expert mode adds movement heat.
- Cockpit: 5 MFDs (Coolant UL, Engineering top, Hot Box UR, Weapon ×2) + secondary screen with
  side button columns + **EJECT button** beside the joystick + per-mech COOLANT LOOP tables
  (weapons+generators per loop 1-6) and stat sheets (tonnage/armor/reservoir liters/heat
  sinks/top speeds incl. "Super Charged").
NEW LEADS (manual describes, port lacks input/UI): **CROUCH** (button by the secondary screen;
`Mech::duckState` attr 0x37 + SQUAT clips exist, nothing drives them), **EJECT** (sounds exist:
EjectButton01_z*.wav), hot-box viewscreen framing (the deferred PNAME marker chain). Per-mech
stat tables = a systematic cross-check source for our streamed subsystem resources.

### Coolant-loop cross-check RESULT (2026-07-18) [T1] -- STRUCTURE strongly faithful
Dumped each mech's subsystem->loop (subsystem's linked-condenser number, `BTCoolingLoopFrame`)
and diffed vs the manual's COOLANT LOOPS tables. The 4.0->4.10 drift shows here too, but the
STRUCTURE is remarkably intact:
- **Backbone identical on ALL 6 mechs:** Generator A/B/C/D on loops 1/2/3/5, **Sensors** (our
  "Avionics") on loop 2, **Myomers** on loop 5, LRMs on loops 1&3, autocannon on loop 4, the
  large energy weapon on loop 6 -- match the manual exactly.
- **Weapon LOADOUT identical on 5 of 6** (Thor, Vulture, MadCat, Owens, Blackhawk carry the exact
  same weapon set 4.0->4.10). **Loki is the one full rework** (4.0 PPC x2 / AFC100 / SRM6 / Medium
  Laser -> 4.10 AFC50 x2 / ER Medium x2 / SRM4).
- **The consistent 4.0->4.10 change:** the small energy weapons were REDISTRIBUTED across loops --
  the 2 ER Small Lasers moved off the sensor/heavy loops (4.0) onto the energy-weapon loops 4&6
  (4.10) on Thor/MadCat/Vulture; SRM/laser placement reshuffled on Blackhawk. Owens is a
  near-PERFECT match (loops 1&3 exact; only a 4.0 "second myomer set" on loop 2 is absent).
- **`Loop 0` = correctly UNCOOLED infrastructure** (condensers, reservoir, gyro, torso, HUD,
  searchlight, thermal sight, ammo bins, message manager, mechtech, controls mapper) -- not a loop.
CONCLUSION: the coolant-loop reconstruction is faithful; every difference is 4.0->4.10 tuning
(loadout rework on Loki, small-laser redistribution elsewhere), NOT a bug. `BT_SPEC_LOG` (mech4)
re-dumps on demand.

## Key Relationships
- Renders: [[gauges-hud]] (the MFD surfaces), [[rendering]] (the main 3D view).
- Input: [[locomotion]] (the mapper).
- Bring-up: Phase 8 (get pod specifics from Nick — [[open-questions]]).