sl-jetson
c47ac41573
- Dockerfile: L4T R32.6.1 (JetPack 4.6) base + ROS2 Humble + SLAM stack (slam_toolbox, Nav2, rplidar_ros, realsense2_camera, robot_localization) - docker-compose.yml: multi-service stack (ROS2, RPLIDAR A1M8, D435i, STM32 bridge) with device passthrough, host networking for DDS, persistent map volume - docs/pinout.md: full GPIO/I2C/UART pinout for STM32F722 bridge (USB CDC + UART fallback), RealSense D435i (USB3), RPLIDAR A1M8, udev rules - docs/power-budget.md: 10W envelope analysis with per-component breakdown, mitigation strategies (RPLIDAR gating, D435i 640p, nvpmodel modes) - scripts/setup-jetson.sh: host one-shot setup (Docker, nvidia-container-runtime, udev rules, MAXN power mode, swap) - scripts/build-and-run.sh: build/up/down/shell/slam/status helper Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
189 lines
5.1 KiB
Markdown
189 lines
5.1 KiB
Markdown
# Jetson Nano Power Budget Analysis
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## Self-Balancing Robot — 10W Envelope
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Last updated: 2026-02-28
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Target: Operate within 10W SoC power envelope (MAXN 10W mode)
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---
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## Power Modes
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Jetson Nano supports two NVPModel power modes:
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| Mode | GPU | CPU cores | CPU freq | Memory freq | TDP |
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|------|-----|-----------|----------|-------------|-----|
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| **MAXN (Mode 0)** | 128 core | 4 | 1.43GHz | 1600MHz | **10W** |
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| 5W (Mode 1) | 128 core | 2 | 0.92GHz | 1600MHz | 5W |
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For this robot, we target **MAXN 10W mode** with careful peripheral management.
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```bash
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# Check current mode
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sudo nvpmodel -q
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# Set 10W MAXN mode
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sudo nvpmodel -m 0
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# Set 5W mode (thermal/battery save)
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sudo nvpmodel -m 1
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# Monitor power in real time
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sudo tegrastats
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```
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---
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## Component Power Budget
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### SoC (Jetson Nano Module)
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| Component | Idle (W) | Load (W) | Peak (W) | Notes |
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|-----------|----------|----------|----------|-------|
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| CPU (4× Cortex-A57) | 1.0 | 3.5 | 4.0 | ROS2 + SLAM compute |
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| GPU (128-core Maxwell) | 0.5 | 2.5 | 3.0 | Depth processing, ML inference |
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| DDR4 RAM (4GB) | 0.3 | 0.6 | 0.8 | |
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| eMMC / SD | 0.1 | 0.2 | 0.3 | |
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| **SoC Subtotal** | **1.9** | **6.8** | **8.1** | |
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### Peripherals (USB / GPIO)
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| Peripheral | Idle (W) | Active (W) | Peak (W) | Interface | Notes |
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|-----------|----------|------------|----------|-----------|-------|
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| RealSense D435i | 0.3 | 1.5 | 3.5 | USB 3.1 | Peak during boot/init |
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| RPLIDAR A1M8 | 0.4 | 2.6 | 3.0 | USB (UART adapter) | Motor spinning |
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| STM32F722 bridge | 0.3 | 0.5 | 0.8 | USB CDC | Powered from Jetson USB |
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| **Peripheral Subtotal** | **1.0** | **4.6** | **7.3** | | |
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### Total System (from Jetson 5V barrel jack)
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| Scenario | SoC (W) | Peripherals (W) | **Total (W)** | Margin |
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|----------|---------|-----------------|---------------|--------|
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| Idle | 1.9 | 1.0 | **2.9** | +7.1W |
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| Nominal (SLAM running) | 6.8 | 4.6 | **11.4** | **-1.4W ⚠️** |
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| Peak (all active, ML) | 8.1 | 7.3 | **15.4** | **-5.4W ❌** |
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---
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## Budget Compliance Strategy
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The nominal load of **11.4W exceeds the 10W envelope** — mitigation required:
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### Mitigation 1: RPLIDAR Power Gating
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The RPLIDAR motor can be stopped when not scanning. The ROS2 driver handles this via DTR line.
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| Mode | Savings |
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|------|---------|
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| RPLIDAR motor off | −2.2W |
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| RPLIDAR idle | 0.4W vs 2.6W |
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### Mitigation 2: RealSense Resolution Reduction
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Lower RGB-D resolution reduces USB bandwidth and D435i processing:
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| Profile | Power |
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|---------|-------|
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| 1280×720 @ 30fps | 1.5W |
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| 640×480 @ 30fps | 1.1W ← **Recommended** |
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| 424×240 @ 30fps | 0.8W |
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### Mitigation 3: Jetson GPU Workload Scheduling
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Avoid running depth inference and SLAM simultaneously at full throttle:
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```bash
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# Cap GPU frequency (reduce from max 921.6MHz)
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sudo jetson_clocks --show
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# Set conservative clocks
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echo 614400000 | sudo tee /sys/devices/17000000.gp10b/devfreq/17000000.gp10b/min_freq
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```
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### Mitigation 4: STM32 Self-Powered
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Power STM32 from robot's 5V bus (separate from Jetson USB rail):
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| Option | Jetson USB load |
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|--------|----------------|
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| STM32 powered from Jetson USB | 0.5W |
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| STM32 powered from robot 5V | **0W** (data only via USB) |
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---
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## Revised Budget with Mitigations
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Applying: 640×480 D435i + RPLIDAR gating + STM32 self-powered:
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| Component | Power (W) |
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|-----------|-----------|
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| CPU (SLAM, 4 cores) | 3.5 |
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| GPU (depth processing) | 2.0 |
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| RAM + misc SoC | 1.0 |
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| RealSense D435i (640×480) | 1.1 |
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| RPLIDAR A1M8 (active) | 2.6 |
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| STM32 bridge (self-powered) | 0.0 |
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| **Total** | **10.2W** |
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**Near-compliant at 10.2W.** Further savings achievable by:
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- Enabling RPLIDAR standby between scan cycles (−0.5W avg)
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- Using 5W nvpmodel during motor-heavy phases
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---
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## Input Power Requirements
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### Jetson Nano Power Input
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| Spec | Value |
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|------|-------|
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| Input connector | 5.5mm / 2.1mm barrel jack |
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| Input voltage | 5V DC |
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| Recommended current | ≥4A (20W supply for headroom) |
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| Absolute max | 5.25V |
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> **Use a 5V 4A supply minimum.** A 2A supply will brownout under load.
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### Robot Power Architecture (Recommended)
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```
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LiPo 3S (12.6V max)
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│
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├─► DC-DC Buck → 5V 5A ──► Jetson Nano barrel jack
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│ (e.g., XL4016)
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│
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├─► DC-DC Buck → 5V 3A ──► STM32 + logic 5V rail
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│
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└─► Hoverboard ESC ──► Hub motors (48V loop)
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```
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This isolates the Jetson 5V supply from motor switching noise.
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---
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## Real-Time Monitoring
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```bash
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# Live power telemetry
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sudo tegrastats --interval 500
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# Key fields:
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# POM_5V_IN X/Y — total input power (current W / average W)
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# POM_5V_GPU X/Y — GPU power
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# POM_5V_CPU X/Y — CPU power
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# Log to file
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sudo tegrastats --interval 1000 --logfile /tmp/power_log.txt &
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# Parse log
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grep "POM_5V_IN" /tmp/power_log.txt | \
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awk '{for(i=1;i<=NF;i++) if($i=="POM_5V_IN") print $(i+1)}' | \
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awk -F'/' '{sum+=$1; count++} END {print "Avg:", sum/count, "mW"}'
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```
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---
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## Summary
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| Metric | Value |
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| Target envelope | 10W |
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| Nominal (no mitigation) | 11.4W |
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| Nominal (with mitigations) | ~10.2W |
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| Compliant scenario | RPLIDAR standby + 640p D435i |
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| Recommended PSU | 5V 4A (20W) |
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| Power mode | nvpmodel MAXN (Mode 0) |
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