Loop Block

The Loop block repeats a sequence of blocks multiple times or for a set duration. It can also stop early when a condition is met.

How It Works

The loop has two exit paths:

• LOOP (right, purple 🔄) — connect to the blocks that form the loop body. The last block in the body MUST be a Loop Back block that returns to this loop.
• DONE (left, green ✅) — connect to what happens after the loop finishes.

      ┌──────────┐
      │   LOOP   │ ◄──────────────┐
      │ 5x / 30s │                │
      └──┬───┬───┘                │
    DONE │   │ LOOP (body)        │
         │   ↓                    │
         │  [Sensor Read]         │
         │   ↓                    │
         │  [Actuator Set]        │
         │   ↓                    │
         │  [LOOP BACK → Loop] ───┘
         ↓
      [Next block]

Important: The Loop Back block at the end of the body is required. Without it, the loop can’t iterate and the flow will be saved as invalid.

Configuration

Section 1: Conditions (Limit Mode)

Choose how the loop knows when to stop:

COUNT Mode

TIME Mode

Section 2: Interval (Timing)

Example: A loop with Count: 10, Interval: 5sec reads a sensor 10 times, waiting 5 seconds between each read. Total time ≈ 50 seconds.

Section 3: Stop Condition (Optional)

An optional early-exit condition. Checked after each iteration — exits early if it’s met.

Important: The stop condition means “Keep Looping While” — the loop continues while the condition is TRUE and exits when it becomes FALSE.

Example:

• Variable: current_ph, Operator: <, Value: 6.5
• Meaning: Keep looping while pH is below 6.5. Once pH reaches 6.5 or above, exit the loop.

This is powerful for “dose until target” patterns:

LOOP (count: 20, interval: 30s, stop when: current_ph >= 6.5)
  ├── Sensor Read → current_ph
  ├── Actuator: pH Up Pump → DOSE 2mL
  └── (back to loop)
DONE → Log "pH target reached"

Error Handling

The loop block’s On Failure controls what happens when the maximum iterations/timeout is reached without the stop condition being met:

Troubleshooting

Loop runs forever

• Make sure the loop body connects back to the loop’s input handle via a LOOP_BACK block
• Ensure COUNT or TIME limit is set
• If using a stop condition, verify the variable is being updated inside the loop body

Loop exits immediately

• Check if the stop condition is already met before the loop starts
• Verify the COUNT is not 0

“No loop nodes” in LOOP_BACK target

• LOOP_BACK targets only loop-type blocks. Make sure a loop block exists in the flow.

Related

• Flow Editor Overview
• Node: Condition
• Node: Utilities
• Variables