From ACMS Digital Systems, makers of Datalink Pro: a Windows app that puts a virtual ACARS terminal in your MSFS 2020 or 2024 cockpit, with an automated airline dispatch office on the other end.
A Stream Deck plugin with two actions, both working on keys and on Stream Deck + dials. Place either as many times as you like; each instance is configured independently.
SimClock shows PC time, real Zulu (UTC), sim Zulu — the clock inside Microsoft Flight Simulator — SimBrief's scheduled off-block, or a countdown to it, as two centered lines:
HEADER
HH:MM
Departure Timeline counts a list of reminders back from scheduled off-block, as three lines:
NEXT D-15
DEPARTURE BRIEF
in 04:12
npm install
npm run build
streamdeck link com.acms.simclock.sdPlugin
Developer mode must be on (streamdeck dev) and Stream Deck must be restarted for it
to take effect. After that, streamdeck restart com.acms.simclock reloads the plugin
without restarting Stream Deck.
To produce a distributable installer:
npm run pack
That writes dist/com.acms.simclock.streamDeckPlugin — a plain ZIP containing the
.sdPlugin folder at its root, which installs on double-click.
The plugin carries an MSFS SimClock profile for the Stream Deck + XL. Four dials, three of
them switched by turning: LOCAL / REAL ZULU / SIM ZULU, STD / TO STD (alerts at 10, 5 and 0
minutes), ETA / TO ETA, and the Departure Timeline. The last two dials and the keys are left blank. It is com.acms.simclock.sdPlugin/profiles/SimClock-PlusXL.streamDeckProfile; open it
to add the profile. python tools/make_profile.py rebuilds it after the version changes.
Per instance of SimClock. The timeline has its own, listed further down.
| Setting | Default | Notes |
|---|---|---|
| Time Source | PC Time | PC Time / Zulu / Sim Zulu / STD / Countdown to STD / ETA / Countdown to ETA |
| Turn to switch | (none) | Dials only. Tick two or more clocks and turning steps through them; see below |
| Departure name | STD | STD / PUSH / SOBT / OUT / DEP; names the departure clock and its countdown (PUSH, TO PUSH) |
| Header | auto | Blank shows LOCAL / REAL ZULU / SIM ZULU; type anything else, e.g. KJFK |
| Style | PANEL | PANEL or CLASSIC; see Style below |
| Font | Segoe UI | Any font family installed on this PC |
| Header Color | #9AA0A6 |
CLASSIC only |
| Time Color | #FFFFFF |
CLASSIC only |
| Background | #000000 |
CLASSIC only |
| Transparent | off | CLASSIC draws no background at all; PANEL leaves out only the black behind its rounded corners |
| Countdown Alerts | (blank) | Up to three minute/colour pairs; Countdown to STD only |
| SimBrief User | (blank) | Global — entered once, shared by every clock and timeline |
Text shrinks to fit rather than clipping. It cannot be measured from Node, so width is estimated from per-character advances chosen to over-estimate: a long header comes out slightly smaller than it had to be instead of running off the key. Small is recoverable, clipped is not.
PANEL (the default) is the look of the Camera Deck for ChasePlane plugin: a plain charcoal key or dial section, a solid band across the top in its colour with the header in white (bright colours such as gold are darkened until white reads on them), the time in the middle in a light shade, and a ring marks something active. Only flat shapes and text: Stream Deck's SVG renderer did not draw blur or gradients in tests.
One colour per function:
| Shows | Colour |
|---|---|
| PC time | teal |
| Zulu | blue |
| Sim Zulu | purple |
| STD | gold |
| Countdown to STD | orange; red once LATE |
| ETA | cyan |
| Countdown to ETA | green |
| Chronometer | green, ringed while running |
| Departure Timeline | pink; the band turns a deep shade of the Due colour while an item is due |
A crossed countdown alert rings the section in its colour and colours the time.
CLASSIC is the plain look from before, header over time in the colours you pick.
Stream Deck plugins are sandboxed and cannot call SimConnect, so a small bridge process
does it. You don't start it — the plugin spawns bridge/simclock_bridge.exe when a
clock that needs sim time is placed, and stops it when the last one goes away.
To rebuild that executable after changing the Python:
npm run build:bridge
It reads the ABSOLUTE_TIME SimVar — seconds since 0001-01-01 00:00:00 UTC, no epoch
offset — and serves it on http://127.0.0.1:47600/time. The plugin polls once a second.
Two details that matter:
- The SimConnect request cache TTL is 2000 ms and must not be lowered. At
_time=0the SDK drains the message queue and every read returnsNone. The plugin absorbs that staleness by anchoring on each sample and advancing from its own monotonic clock. - Time compression is handled. The bridge derives the sim's rate from consecutive changed readings against wall clock, so 4x cruise doesn't make the display jump each time a sample lands.
When the bridge is down or MSFS isn't running, Sim Zulu shows --:--. It never falls back
to real time — a wrong number under a SIM header is worse than no number.
Sim Zulu is the simulator's own UTC. It diverges from real Zulu as soon as you set a departure time or compress time; that's the point of having both.
When the sim runs faster or slower than real time, the SIM clock's header says so: SIM ZULU 4X,
SIM ZULU 0.5X. At normal speed it shows nothing extra. The bridge's rate is measured, so it is
snapped to the nearest MSFS rate (a power of two) to keep it steady.
STD shows scheduled off-block from your OFP; Countdown to STD shows that time minus
sim Zulu, so it tracks time compression. Past STD it counts up as +MM:SS and the auto
header changes to LATE — a header you typed yourself is always kept.
STD is Scheduled Time of Departure: the scheduled off-block time, when the aircraft is due to
push back, not takeoff. Departure name can call it PUSH, SOBT (Scheduled Off-Block Time),
OUT (the datalink word, as in Out-Off-On-In) or DEP instead; the countdown follows, as
TO PUSH and so on. All five are the same time.
SOBT comes from times/sched_out, the same field Datalink Pro treats as authoritative.
sched_off is takeoff and sched_in is arrival; neither is the departure time.
ETA shows the OFP's estimated in-block time at the destination (times/est_in), and
Countdown to ETA that time minus sim Zulu, counting up as +MM:SS once past it. It is the
estimate from the flight plan: a late departure does not move it.
Enter your SimBrief username once in any clock's Property Inspector. Your SimBrief profile must have publicly visible enabled (Account → Privacy) or the API returns nothing. No password is ever used.
The OFP is polled every 5 minutes — it only changes when you regenerate it, and hammering SimBrief's API risks a rate limit. Placing or reconfiguring a SimBrief clock pulls a fresh one immediately, rate-limited to once every 30 seconds.
Reminders at fixed minutes before scheduled off-block. The three lines show the next one
with the time until it; when it falls due all three change to the Due colour and stay
there until it is acknowledged, or until the next one falls due — a missed reminder is
superseded rather than piling up. With everything past and acknowledged it reads
COMPLETE. With no OFP it reads NO OFP, and with no sim time NO SIM.
The list is a plain textarea, one reminder per line, minutes first. 35 BOARDING,
D-35 BOARDING, 35: BOARDING and 35=BOARDING all parse; a line with no leading number,
or no label, is skipped rather than guessed at. Labels are upper-cased, and the list is
sorted largest-minutes-first, which is the order they fall due. The default is the AA 737
sequence — D-15 briefing, D-10 Before Start, D-3 doors, D-2 push — plus the ground-service
order ahead of it.
That default is written into the setting the first time an instance appears, so the panel
shows a real, editable example rather than an empty box: sdpi-textarea has no placeholder
property, so the attribute is silently dropped. Clearing the box falls back to the same
list, and only an absent setting is ever seeded.
| Input | Key | Dial |
|---|---|---|
| Press | Acknowledge what is due, else reload SimBrief | Same |
| Long press (0.6 s) | Clear every acknowledgement | Same |
| Rotate | — | Browse the list ahead; returns by itself after 10 s |
| Touch | — | Acknowledge |
Both are timed down-and-up, so the hold works on a button with no dial. A press while browsing just returns to the live view.
Acknowledgements belong to the departure, not to the page. Switching Stream Deck pages makes every instance disappear and reappear, so they are kept across it; a change to scheduled off-block — a new OFP — clears them.
On a key the label wraps onto up to three lines, taking the largest size that fits both
the width and the band it has. A key is 144 px wide, so WATER FUEL CATERING on one line
lands at about 10 px; over two lines it is 20 px. One line stays centred on the same
baseline it always used. The dial is 200x100 with no room to stack, so it is always one
line.
| Setting | Default | Notes |
|---|---|---|
| Reminders | the 737 sequence | One per line, minutes first |
| Due Color | #FFD400 |
PANEL: band and ring while an item is due; CLASSIC: the top two lines |
| Demo | off | Runs on the PC clock against a pretend off-block |
| Demo Minutes | 62 | Pretend off-block, minutes from when the demo starts |
Demo needs no OFP and no MSFS, so a list can be tuned on the desktop. On a dial, rotation moves the pretend clock a minute per detent instead of browsing, which walks a whole departure in seconds. Turning demo on or off, or changing its minutes, restarts the pretend clock; editing the list or the colours leaves it running so the change can be watched.
A live timeline needs sim time, but only once there is an OFP to count down to — with no
scheduled off-block it reads NO OFP whether the bridge is up or not, so a timeline left
on the deck between flights does not hold simclock_bridge.exe open.
Tick two or more clocks under Turn to switch and one dial holds them all: each detent
moves to the next, in the order the panel lists them, wrapping at both ends. This takes the
place of Time Source. The dial remembers where it was left, across page switches and
restarts. Each clock uses its own automatic header, since one typed name cannot fit them
all, and keeps its own behaviour: alerts on the departure countdown, LATE, SIM ZULU 4X, a
press reloading SimBrief on the SimBrief clocks.
On such a dial the chronometer is set by pressing and turning; see below.
On a Stream Deck + dial:
| Input | Action |
|---|---|
| Rotate | Set the target, one minute per detent (only while idle). On a Turn to switch dial, press and turn |
| Press | Start / stop |
| Long press (0.6 s) | Reset, returning to the clock |
| Touch | Start / stop |
The chronometer belongs to the clock sources. On a dial set to STD, ETA or either
countdown a press reloads SimBrief instead, and rotation is inert -- a dialled-in
target would otherwise make the chronometer active and hijack the display.
Set a target and it counts down; start from zero and it counts up. While active the
chronometer takes over the same two lines — CHR over MM:SS — and owns the dial: on a Turn
to switch dial a plain turn no longer switches clocks until a long press resets it. Letting
go after a press-and-turn does not start it. Rotation is ignored while
running so a knock can't rewrite the target mid-timing.
npm test
135 checks covering time formatting, the chronometer state machine, settings fallbacks, SVG rendering including XML escaping of user input and key label wrapping, tick-boundary scheduling, OFP epoch parsing, the countdown/late transition, countdown alert thresholds, registry font parsing, timeline parsing and which reminder is due, and the Panel style. No Stream Deck or MSFS required.
A clock showing HH:MM changes once a minute, so it is drawn once a minute -- not sixty
times. Three things keep it cheap:
- Settings are cached from
willAppear/didReceiveSettings. The tick never asks Stream Deck for them, so the common path costs no IPC at all. - Identical draws are skipped. Each instance remembers a signature of what it last sent; an unchanged one is never transmitted.
- The ticker schedules itself. With only real-time clocks placed it sleeps to the next minute boundary. It drops to 1 Hz when a chronometer is running, or when a Sim Zulu clock is placed -- time compression makes sim minutes elapse faster than real ones, so real minute boundaries would miss them. A placed timeline counts down in seconds, so it holds 1 Hz for as long as it is on screen.
With three clocks placed this is roughly three Stream Deck messages a minute rather than three hundred and sixty.
src/ plugin source (TypeScript)
plugin.ts entry point; one self-scheduling ticker drives every instance
clock-action.ts the clock action: events, chronometer wiring, drawing
timeline-action.ts the timeline action: events, acknowledgements, browsing, demo
render.ts two-line and three-line SVG, with key label wrapping
format.ts HH:MM and MM:SS formatting (pure, tested)
settings.ts settings resolution and validation (pure, tested)
timeline.ts reminder parsing and which one is due (pure, tested)
thresholds.ts countdown alert colours (pure, tested)
fonts.ts installed font families, read from the registry (pure, tested)
schedule.ts minute-boundary tick math (pure, tested)
ofp.ts SimBrief epoch parsing (pure, tested)
simbrief-feed.ts polls the OFP for scheduled off-block
bridge-process.ts starts/stops the bridge exe on demand
chrono.ts chronometer state machine (pure, tested)
sim-feed.ts polls the bridge, extrapolates between samples
time-source.ts maps a source to a Date
bridge/ Python SimConnect bridge
tools/make_icons.py regenerates the plugin PNG icons
com.acms.simclock.sdPlugin/ the plugin itself (manifest, UI, images, built bin/)