Ryan Malloy
5edac3007c
New pages covering all 4 quadrants: - Tutorial: tutorials/multi-vna-basics.mdx - How-To: hardware/trigger-wiring.mdx, hardware/external-clock.mdx - Explanation: mcnanovna/multi-vna.mdx Updated sidebar navigation and cross-links in overview, tools, and quickstart pages.
233 lines
7.3 KiB
Plaintext
233 lines
7.3 KiB
Plaintext
---
|
|
title: VNA Hardware Trigger Wiring
|
|
description: Wire multiple NanoVNAs for Tier 2 synchronized measurements
|
|
---
|
|
|
|
import { Steps, Tabs, TabItem, Aside } from '@astrojs/starlight/components';
|
|
|
|
Hardware trigger synchronization (Tier 2) achieves ±10-50µs timing between VNAs—100x tighter than software coordination. This guide shows you how to wire the trigger lines between devices.
|
|
|
|
## When You Need This
|
|
|
|
| Use Case | Tier 1 (Software) | Tier 2 (Hardware Trigger) |
|
|
|----------|-------------------|---------------------------|
|
|
| Antenna comparison | ✓ | ✓ |
|
|
| SWR/impedance | ✓ | ✓ |
|
|
| Signal level measurements | ✓ | ✓ |
|
|
| Transmission path timing | Limited | ✓ |
|
|
| Differential S21 | Limited | ✓ |
|
|
| Multi-VNA transfer functions | ✗ | ✓ |
|
|
|
|
For phase-aligned measurements, you'll also need [external clock (Tier 3)](/hardware/external-clock/).
|
|
|
|
## Parts Needed
|
|
|
|
- Jumper wires (Dupont or similar)
|
|
- Soldering iron and solder (fine tip recommended)
|
|
- NanoVNA-H with custom firmware supporting trigger commands
|
|
|
|
<Aside type="caution">
|
|
This modification requires soldering to small test points. If you're not comfortable with fine soldering, consider having an experienced friend help.
|
|
</Aside>
|
|
|
|
## Pin Locations
|
|
|
|
The trigger system uses two GPIO pins on the STM32F303:
|
|
|
|
| Pin | Function | Location | Description |
|
|
|-----|----------|----------|-------------|
|
|
| **PA0** | TRIG_IN | See board diagram | External trigger input (rising edge) |
|
|
| **PB14** | TRIG_OUT | See board diagram | Pulse output at sweep start |
|
|
|
|
### NanoVNA-H Rev 3.4 Board
|
|
|
|
```
|
|
┌─────────────────────────────────────────┐
|
|
│ │
|
|
│ ┌───────────────────────┐ │
|
|
│ │ │ │
|
|
│ │ LCD │ │
|
|
│ │ │ │
|
|
│ └───────────────────────┘ │
|
|
│ │
|
|
│ │
|
|
│ [PA0]● ●[PB14] │
|
|
│ TRIG_IN TRIG_OUT │
|
|
│ │
|
|
│ ┌──┐ ┌──┐ │
|
|
│ │P1│ │P2│ │
|
|
│ └──┘ └──┘ │
|
|
│ Port 1 Port 2 │
|
|
└─────────────────────────────────────────┘
|
|
```
|
|
|
|
<Aside type="note">
|
|
Pin locations vary by board revision. On some boards, these pins are on test points. On others, you may need to solder directly to the MCU. Consult your board's schematic.
|
|
</Aside>
|
|
|
|
## Wiring Steps
|
|
|
|
<Steps>
|
|
1. **Identify the leader VNA**
|
|
|
|
Choose one VNA as the "leader"—it will generate the trigger pulse that starts all sweeps. The others are "followers."
|
|
|
|
2. **Solder wires to pins**
|
|
|
|
On the **leader VNA**:
|
|
- Solder a wire to **PB14** (TRIG_OUT)
|
|
|
|
On each **follower VNA**:
|
|
- Solder a wire to **PA0** (TRIG_IN)
|
|
|
|
Use thin wire (30 AWG or similar) to avoid stressing the pads.
|
|
|
|
3. **Connect the trigger bus**
|
|
|
|
Wire all followers' TRIG_IN lines to the leader's TRIG_OUT:
|
|
|
|
```
|
|
Leader VNA Follower VNA #1
|
|
┌─────────┐ ┌─────────┐
|
|
│ PB14 │──────────────────│ PA0 │
|
|
│(TRIG_OUT)│ │(TRIG_IN) │
|
|
└─────────┘ │ └─────────┘
|
|
│
|
|
│ Follower VNA #2
|
|
│ ┌─────────┐
|
|
└────────│ PA0 │
|
|
│(TRIG_IN) │
|
|
└─────────┘
|
|
```
|
|
|
|
For more than 2 followers, daisy-chain or use a splitter.
|
|
|
|
4. **Verify ground reference**
|
|
|
|
All VNAs share ground via USB (same host computer). No additional ground wire needed.
|
|
|
|
If using VNAs on different computers, add a common ground wire.
|
|
|
|
5. **Test trigger signaling**
|
|
|
|
Use a multimeter or oscilloscope to verify:
|
|
- PB14 can be toggled (use `raw_command("trig_out pulse")`)
|
|
- PA0 sees the pulse on followers
|
|
|
|
</Steps>
|
|
|
|
## Firmware Requirements
|
|
|
|
Stock NanoVNA firmware doesn't include trigger commands. You need custom firmware with:
|
|
|
|
| Command | Description |
|
|
|---------|-------------|
|
|
| `trig_mode {software\|hardware\|leader\|follower}` | Set trigger mode |
|
|
| `trig_out {on\|off\|pulse}` | Manual trigger control |
|
|
| `trig_status` | Read trigger state |
|
|
|
|
Check capability with `detect_capabilities()`:
|
|
|
|
```json
|
|
{
|
|
"device_id": "0001234567",
|
|
"capabilities": {
|
|
"hardware_trigger": true,
|
|
"external_clock": false
|
|
},
|
|
"tier": 2
|
|
}
|
|
```
|
|
|
|
<Aside type="tip">
|
|
See the NanoVNA-H community firmware for trigger-enabled builds, or build your own from the ChibiOS-based source.
|
|
</Aside>
|
|
|
|
## Using hardware_sync_sweep
|
|
|
|
Once wiring is complete and firmware supports triggers:
|
|
|
|
Say: "Run a hardware-synced sweep from 144 to 148 MHz with device 0001234567 as leader"
|
|
|
|
The assistant calls:
|
|
|
|
```
|
|
hardware_sync_sweep(
|
|
leader_device_id="0001234567",
|
|
follower_device_ids=["0009876543"],
|
|
start_hz=144000000,
|
|
stop_hz=148000000,
|
|
points=101
|
|
)
|
|
```
|
|
|
|
This automatically:
|
|
|
|
1. Sets leader to "leader" mode
|
|
2. Sets followers to "follower" mode
|
|
3. Runs parallel scans (hardware synchronized)
|
|
4. Restores "software" mode
|
|
|
|
## Testing the Trigger Line
|
|
|
|
### Manual test via raw_command
|
|
|
|
```
|
|
# On leader - generate pulse
|
|
raw_command(device_id="0001234567", command="trig_out pulse")
|
|
|
|
# On follower - check status
|
|
raw_command(device_id="0009876543", command="trig_status")
|
|
```
|
|
|
|
Expected output: `trigger_count` should increment.
|
|
|
|
### Oscilloscope verification
|
|
|
|
- Pulse width: ~10µs
|
|
- Rising edge: < 1µs
|
|
- Voltage: 3.3V logic level
|
|
|
|
## Troubleshooting
|
|
|
|
### Trigger not detected
|
|
|
|
1. Verify wiring continuity with multimeter
|
|
2. Check firmware has `trig_mode` command: `raw_command("help")`
|
|
3. Ensure ground is shared between VNAs
|
|
4. Try shorter trigger wire (< 30cm recommended)
|
|
|
|
### Erratic triggering
|
|
|
|
1. Add 100Ω series resistor on TRIG_OUT to reduce ringing
|
|
2. Keep trigger wire away from RF paths
|
|
3. Use shielded wire for long runs (> 30cm)
|
|
4. Check for EMI from nearby equipment
|
|
|
|
### Sweeps still not synchronized
|
|
|
|
1. Verify both VNAs have same sweep settings (start, stop, points)
|
|
2. Check trigger mode is correctly set before sweep
|
|
3. Ensure leader starts sweep before followers timeout
|
|
|
|
### Capability shows false
|
|
|
|
1. Firmware may not support triggers
|
|
2. Flash custom firmware with trigger support
|
|
3. Run `detect_capabilities()` after firmware update
|
|
|
|
## Electrical Specifications
|
|
|
|
| Parameter | Value |
|
|
|-----------|-------|
|
|
| TRIG_OUT pulse width | 10µs |
|
|
| TRIG_IN threshold | 1.6V (TTL-compatible) |
|
|
| Maximum trigger cable length | 1m (unshielded), 5m (shielded) |
|
|
| Edge-to-sweep latency | < 50µs |
|
|
|
|
## Next Steps
|
|
|
|
- [External Clock Modification](/hardware/external-clock/) — Add Tier 3 phase coherence
|
|
- [Multi-VNA Coordination](/mcnanovna/multi-vna/) — Understand all synchronization tiers
|
|
- [Tool Reference](/mcnanovna/tools/) — Hardware trigger tools
|