BC-250 Telemetry

A telemetry daemon and web dashboard for the AMD BC-250 (Oberon / Cyan Skillfish, gfx1013, PCI ID 1002:13fe) — the decommissioned mining-board APU carved out of the PS5. Runs on Bazzite, SteamOS, and CachyOS from the same binary.

It merges two data sources into one JSON snapshot every ~700 ms:

• Hardware (PMBus over I2C): per-rail voltage, current, power, and temperature for the CPU and GPU rails, read straight from the VRM/PMIC. The chip address (0x60) is fixed in hardware; the I2C bus number isn't, so the daemon scans /dev/i2c-* and finds it automatically. Getting this bus exposed in the first place requires a small physical mod — see hardware.md.
• Software (Linux hwmon/sysfs): die temperatures, clocks, power draw (PPT), and fan RPM/PWM, via the amdgpu, k10temp, nct6686, and nvme hwmon directories.

Everything is written atomically to /run/apu_telemetry.json, served by a small bundled web server (web/server.py) on port 8090 with two dashboard variants — / (classic HUD) and /v2/ (animated board diagram), both always reachable regardless of which one is the default.

The web layer adds a third data source on top of that, at a much slower cadence — CPU core / GPU Compute Unit counts, and overclock config/service state — since none of it changes at 700 ms speed. See Topology & overclock endpoints below.

If the I2C bus isn't found, the daemon doesn't crash-loop — it logs the issue, retries every ~10 s, and keeps serving everything that doesn't depend on I2C (CPU/GPU clocks, temperatures, fans).

Screenshots

Classic (/)	v2 — animated board diagram (/v2/)

Quick start

Download the latest release from GitHub Releases, extract it, and run:

cd bc250-telemetry
sudo ./install.sh

install.sh compiles the daemon (or falls back to the prebuilt apu_telemetry binary next to it), sets up the nct6683 fan-controller module, installs both systemd units, and asks which dashboard to serve by default at / — classic (v1) or the animated diagram (v2); the other stays reachable either way. To skip the prompt (e.g. for a scripted install):

sudo ./install.sh --dashboard=v2   # or v1

Check that it's running:

sudo systemctl status apu-telemetry bc250-web.service
cat /run/apu_telemetry.json | jq .

Web UI:

http://<board-ip>:8090/       — classic HUD
http://<board-ip>:8090/v2/    — animated board diagram

Update (re-run over an already-running install):

sudo ./install.sh

Uninstall:

sudo ./uninstall.sh

Manual install, step by step

# Fan controller module (not autodetected on this board)
sudo sh -c 'echo "nct6683" > /etc/modules-load.d/99-sensors.conf'
sudo sh -c 'echo "options nct6683 force=true" > /etc/modprobe.d/sensors.conf'
sudo modprobe nct6683 force=true

# Daemon
g++ -O2 -static bc250_telemetry.cpp -o ./apu_telemetry
sudo cp apu_telemetry /usr/local/bin/
sed "s|TELEMETRY_BIN_PATH|/usr/local/bin/apu_telemetry|" apu-telemetry.service \
    | sudo tee /etc/systemd/system/apu-telemetry.service > /dev/null
sudo systemctl daemon-reload
sudo systemctl enable --now apu-telemetry

I2C bus override

The daemon scans /dev/i2c-* on its own and uses whichever one answers at the PMIC's address (0x60). To force a specific bus instead:

./apu_telemetry --bus 4
# or
BC250_I2C_BUS=4 ./apu_telemetry

JSON output format

{
  "hardware": {
    "cpu": { "valid": true, "vin": 12.22, "vout": 0.780, "iout": 2.8, "pout": 2.2, "temp": 45.0 },
    "gpu": { "valid": true, "vin": 12.22, "vout": 0.646, "iout": 12.0, "pout": 7.8, "temp": 48.0 },
    "total_power": 10.0,
    "total_power_valid": true
  },
  "software": {
    "cpu_temp_c": 51.4,
    "cpu_freq_mhz": 3400,
    "gpu_temp_c": 47.0,
    "gpu_sclk_mhz": 400,
    "gpu_ppt_w": 32.1,
    "nvme_temp_c": 38.0,
    "nct_t14_c": -1.0,
    "nct_t15_c": -1.0
  },
  "cooling": {
    "fan_rpm": 945,
    "fan_pwm_pct": 28
  }
}

• cpu_freq_mhz is the average across all CPU cores, not one arbitrary core.
• total_power_valid is false when the CPU or GPU VRM reading is currently invalid — total_power then reflects only the working side, not a real zero.
• Any field can be -1 if that particular sensor isn't available; everything else keeps working independently.

Topology & overclock endpoints

Two more endpoints, served straight by web/server.py (not the daemon) — /api/topology and /api/overclock. Both are config/topology facts rather than telemetry: they only change on a reboot, a live CU/WGP toggle, or an OC config edit, so the dashboard fetches each once per page load instead of polling them every 700 ms.

/api/topology — web/topology.py:

{
  "cpu_physical_cores": 8,
  "gpu_cu_active": 40
}

• cpu_physical_cores comes straight from /proc/cpuinfo's own "cpu cores" field (not threads ÷ 2 — a core disabled by binning isn't guaranteed to leave exactly half the threads intact).
• gpu_cu_active normally comes from the amdgpu driver via libdrm_amdgpu (AMDGPU_INFO_DEV_INFO). If bc250-cu-live-manager.service is active, that value is skipped in favor of its saved /etc/bc250-cu-live-manager.conf WGP table instead — the live-manager toggles CU dispatch by writing SPI/CC/RLC registers directly, after the driver has already cached its own count, so the driver's own number can be stale in that specific case.
• Either field is null if it can't be determined (no /dev/dri render node, libdrm_amdgpu.so.1 missing, etc.) — the dashboard just hides the corresponding badge.

/api/overclock — web/overclock.py:

{
  "cpu": {
    "config_present": true,
    "active": true,
    "target_freq_mhz": 4000,
    "max_temp_c": 90
  },
  "gpu": {
    "config_present": true,
    "active": true,
    "max_freq_mhz": 2000,
    "min_freq_mhz": 400
  }
}

• cpu reads /etc/bc250-smu-oc.conf (INI) and checks bc250-smu-oc.service. That service is a one-shot applier with no RemainAfterExit — it pushes the curve to the SMU once and exits, so active here means "the last run actually completed successfully" (systemctl show Result/ExecMainStatus gated on LoadState/ExecMainStartTimestamp so a never-installed unit doesn't look "active" by default), not "the process is still running".
• gpu reads /etc/cyan-skillfish-governor-smu/config.toml's [frequency-range] table and checks cyan-skillfish-governor-smu.service. That one is a real long-running daemon, so active there means the usual systemctl is-active.
• config_present: false (config file missing or unreadable) means the tool simply isn't installed — the dashboard hides that panel entirely rather than showing zeros.