seeedstudio — RocketWelder plugins for Seeed Jetson carriers

GenericSeeedWelder — ModelingEvolution.WeldingMachine.Seeed.Plugin

A welding machine (e.g. a plasma cutter) whose only control input is a start contact, driven from one isolated digital output of the station computer itself: a Seeed reComputer Industrial J40/J30 or reServer Industrial J4012 on JetPack 6.

ArcOn = output ON, ArcOff = output OFF. No robot, network or controller sits between rw2 and the output — the write is a local ioctl on /dev/gpiochip0, followed by a read-back.

Configuration (rw2 → Devices → Add device → "Generic welder (Seeed digital output)")

Property	Value
SeeedDoOutput	1–4 = terminal DO1–DO4. Required, no default — read it off the cabinet wiring.

How to connect

1. Find the terminal block. The green 16-pin DI/DO/CAN block on the front panel, under the USB ports. The reComputer Industrial and the reServer Industrial J4012 use the same block and the same pin-out.

2. Pin-out. Top row: DI1–DI4, DO1–DO4. Bottom row: GND_DI, GND_DO, then CAN (CG/CH/CL).

Pin (Seeed numbering)	Label	Use here
9 / 11 / 13 / 15 (top row, columns 5–8)	DO1 / DO2 / DO3 / DO4	the output — configure the same number in rw2
8 / 10 (bottom row, under DI4 and DO1)	GND_DO	0 V of the external supply that powers the load
1 / 3 / 5 / 7	DI1–DI4	not used by this plugin (12 V inputs)
2 / 4 / 6	GND_DI	not used
12 / 14 / 16	CG / CH / CL	CAN — not used

3. Wiring (Seeed's reference). Each DO is an isolated, open-collector sink: the load sits between the external +V (max 40 V) and DOx, and GND_DO goes to that supply's 0 V. Max 40 mA per output.

4. Wiring a plasma / welder start contact. The output cannot switch the start circuit directly — drive an interface relay or SSR and let its contact close the welder's start input (the contact a Fairino control-box DO switches today).

   cabinet +24 V ──────────────┐
                               │
                        ┌──────┴──────┐  interface relay / SSR input
                        │  A1     (+) │  coil/input current ≤ 40 mA (aim < 20 mA)
                        │  A2     (−) │  flyback diode across the coil if the
                        └──────┬──────┘  relay module does not have one
                               │
   Seeed terminal  DO1 (pin 9) ┘
   Seeed terminal  GND_DO (pin 8 or 10) ──── cabinet 0 V (of the same 24 V supply)

   relay contact (COM / NO) ──── welder / plasma START input  (dry contact, as wired to the Fairino DO before)
   ideally in series with the E-stop / safety chain — see "Safe state" below

Configure SeeedDoOutput = 1 for DO1 (2 for DO2, …). Check with a meter before the welder is connected: with rw2 running the output is OFF; an ArcOn step closes the relay.

Terminals → Jetson pins

Both carriers wire the DO terminals to the same pins (Seeed wiki, "Hardware and Interfaces Usage" for each product). The plugin finds the line by name, so it does not depend on JetPack's GPIO numbering.

Terminal	Line (BGA)	JetPack 6	JetPack 5 sysfs
DO1	PI.00	gpiochip0 51	399
DO2	PI.01	gpiochip0 52	400
DO3	PI.02	gpiochip0 53	401
DO4	PH.07	gpiochip0 50	398

Wiring

Each DO is an optocoupled sink, 40 V / 40 mA max per pin: load between +V and DOx, return on GND_DO (pins 8/10). Seeed recommends a series resistor. 40 mA is a signal, not a contactor coil — use an interface relay or SSR with a low input current (Fairino's control-box guide recommends < 20 mA for the same job). Verify the relay's coil/input current on its datasheet.

Safe state — what software can and cannot do

Event	Output
Device attaches (boot, app start)	requested LOW
ArcOff, run STOP	LOW, confirmed by read-back, retried once
Device disposed	LOW, then released
SIGTERM / SIGHUP (docker stop, app restart)	LOW (signal hook) — measured on a reServer J4012
SIGKILL, crash, power loss of the Jetson only	UNCHANGED — the kernel releases the line and leaves the pin as it was (measured)

The last row is why the start contact should also go through the E-stop / safety chain in hardware. A Fairino control-box DO differs here: the controller clears its own outputs on a stop.

What the read-back proves

It reads the GPIO controller's output register — the SoC pin is driven. It does not see the optocoupler, the terminal, the relay or an arc. Write + read-back takes < 1 ms.

Host requirements

• rw2 with RocketWelder.SDK ≥ 2.18.0.
• The app container must see /dev/gpiochip* — the standard station compose runs app privileged, which is enough; otherwise add devices: ["/dev/gpiochip0"].
• One device per terminal: a second device on the same DO fails with "already held".

Install

Loopback-only on the station: POST http://localhost/api/plugins/install with {"packageId":"ModelingEvolution.WeldingMachine.Seeed.Plugin","version":"x.y.z"}, then restart the app.

Release

./release.sh cuts a vX.Y.Z tag; .github/workflows/publish-nuget.yml builds, tests and pushes to the ModelingEvolution feed on a self-hosted runner. Never pack from a workstation.

Bench probe

src/SeeedDoProbe drives the real welder code on a board:

dotnet publish src/SeeedDoProbe -c Release -r linux-arm64 --self-contained -p:PublishSingleFile=true -o out
scp out/SeeedDoProbe <board>:/tmp/
sudo /tmp/SeeedDoProbe cycle 1 300 3     # DO1 on/off 3x
sudo /tmp/SeeedDoProbe hold 1 on         # hold ON until SIGTERM
sudo cat /sys/kernel/debug/gpio | grep PI.00   # independent view: "rw2 DO1 ) out hi"

Do not run it while rw2 holds the same terminal — the request fails with "already held", by design.

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Images in docs/images/ are from the Seeed Studio wiki (reComputer Industrial J40/J30 Hardware and Interfaces Usage, reServer Industrial Hardware Interface Usage), © Seeed Studio.