DCENT_OS LED Reference: What the Lights on the Control Board Mean

The four LEDs

The firmware addresses four LEDs by name. Three are real sysfs devices; the fourth is not, and that is worth knowing before you go looking for it.

The green heartbeat is a thermometer

This is the single most useful thing on the page. While mining, the green LED's blink rate is computed from chip temperature — a faster heartbeat means a hotter miner. You can read the approximate thermal state of a machine from across a room, with no screen.

Between 55 °C and 75 °C the scale is linear: scale = 1.0 − (T − 55.0) / 20.0 × 0.75 (led.rs:426), applied to a base cycle of heartbeat_on_ms + heartbeat_off_ms — 100 + 900 = 1000 ms on the shipped configuration. The cycle floors at 100 ms, the on-phase at 30 ms and the off-phase at 50 ms (led.rs:428-436).

Status patterns

Ten background states. The firmware holds exactly one at a time, and it resumes after any interruption.

D7 is a separate question: is the daemon alive?

The internal red LED runs its own rhythm, on its own timer, and is not silenced by the LED master switch, by night mode, or by a locate sequence (led.rs:269-280). It is a double-pulse, like a heartbeat: on 100 ms, off 100 ms, on 150 ms, off 650 ms — a 1-second cycle (led.rs:246-251). Verified (in source).

Read the two together:

• D7 beating, D5/D6 dark — the daemon is running and the user-facing LEDs are off (night mode, or [led] enabled = false).
• D7 dark — either the daemon has stopped, or it shut down cleanly (all_off() clears every LED on shutdown, led.rs:701-706).

Find My Miner: the ten locate patterns

Locate plays a named rhythm on the front LEDs so you can pick one machine out of a rack. The firmware's own convention: green reads as the high notes, red as the low notes, both together as an accent (led_patterns.rs:3-4).

Inferred (arithmetic), and machine-derived: a playthrough is the sum of that pattern's frame durations, which is exactly what the firmware itself computes (BlinkSequence::duration_ms(), led.rs:46-49, summing LedFrame.duration_ms declared at led.rs:33). We do not add these by hand. The ten figures above are emitted by a script that parses every *_FRAMES array in led_patterns.rs and refuses to print anything unless three controls pass — that the summation formula is what we think it is, that every frame helper passes its argument straight through, and that each array's declared [LedFrame; N] length equals the number of frames actually parsed. Check them against the repository; that is the point of printing them.

Behaviour worth knowing before you use it, all Verified (in source):

• The pattern loops until the locate duration expires or a stop arrives (led.rs:566-616). The shipped duration is 30 s (dcentrald.toml:137).
• A stop is honoured within 50 ms, even mid-frame (led.rs:581-582).
• An unrecognised pattern id does not fail — it logs a warning and falls back to imperial_march (led.rs:546-552). If you asked for something exotic and got Star Wars, you mistyped it.
• Share flashes and celebrations are suppressed while locate is running (led.rs:345, :352, :359, :367), so the rhythm stays readable.
• When locate ends, the background pattern resumes (led.rs:618-623).

Event flashes

The chain-online code is a genuine init diagnostic worth memorising: chain 6 flashes once, chain 7 twice, chain 8 three times (led.rs:684-689). On a three-board S9 you should see one, then two, then three green flashes as the chains come up. A missing group tells you which board did not enumerate before any log does.

A flash restores whatever the LED was doing before it, rather than forcing it off (led.rs:632-639) — so a share flash never disturbs the heartbeat you were reading.

Night mode has a trap in it

The shipped configuration block

This is the [led] section exactly as it ships in the repository's dcentrald.toml. Verified (shipped config) — DCENT_OS_Antminer/dcentrald/dcentrald.toml:131-142.

[led]
# LED status indicators on front panel
enabled = true
heartbeat_on_ms = 100              # green LED on-time during mining heartbeat
heartbeat_off_ms = 900             # green LED off-time (1Hz cycle = 100+900)
locate_pattern = "imperial_march"  # default "Find My Miner" blink pattern
locate_duration_s = 30             # how long locate plays before auto-stop
flash_on_accepted_share = true     # brief green flash on accepted share
flash_on_rejected_share = true     # brief red flash on rejected share
night_mode_disable = false         # turn off LEDs during thermal night mode hours
celebration_on_lucky_share = true  # celebrate shares 10x+ above target difficulty
chain_status_blink_codes = true    # flash green N times when chain N comes online

On a running miner the live configuration is /data/dcentrald.toml, which overrides the read-only copy baked into the image and survives reboots and A/B upgrades (DCENT_OS_Antminer/docs/CONFIGURATION.md:3-6).

What this page does not tell you

• Whether any of it is true on your miner. We have not put a bench S9 in front of this table and checked it off. Until we do, this is a reading of source code.
• What the stock Bitmain firmware's LEDs mean. Different firmware, different meanings. This page describes DCENT_OS only.
• Whether D8 does anything. See the box at the top.

Which control boards this has evidence on is a separate question from what the firmware is written to do; see hardware status for the per-lane picture. Nearby: all documentation.