Development Workflows Power Monitoring Guide

E-Ink Board Power Monitoring Guide

Overview

This guide describes how to monitor power consumption of the imx93-jaguar-eink board during firmware optimization using the Keysight 34461A digital multimeter.

Equipment Setup

Hardware

• Power Meter: Keysight 34461A Digital Multimeter
• Network: Connected at 192.168.1.116:5025
• Interface: SCPI over TCP/IP
• Measurement: Current sensing with 5V supply voltage assumption

Access Setup

• Monitoring Host: Michael's laptop (oliver-XPS-13-9380)
• SSH Access: ssh michael-laptop (multiplexed connection)
• Location: 62.3.79.162:23

Power Monitoring Script

Installation

The power monitoring script is located on Michael's laptop at ~/power_monitor.sh.

Usage

# Connect to monitoring laptop
ssh michael-laptop

# Basic monitoring (2-second intervals, 5 minutes)
./power_monitor.sh

# Custom intervals and duration
./power_monitor.sh [interval_seconds] [duration_seconds]

# Examples:
./power_monitor.sh 1 60        # 1-second intervals for 1 minute
./power_monitor.sh 5 1800      # 5-second intervals for 30 minutes

Output Format

The script provides human-readable output with:

• Time: Current timestamp
• Current: Formatted with appropriate units (mA, µA, nA, pA)
• Power: Calculated power consumption (W, mW, µW, nW)
• Status: Power state indicator

========================================
E-Ink Board Power Monitoring
========================================
Time                 Current      Power (5V)   Status         
--------------------------------------------------------------------
15:46:16            10.2 nA      51.0 nW      SLEEP/OFF      
15:46:18            12.5 nA      62.5 nW      SLEEP/OFF      
15:46:20            850.3 µA     4.3 mW       ACTIVE         

Status Indicators

• HIGH POWER: > 100 mA (active processing, WiFi transmission)
• ACTIVE: 10-100 mA (normal operation, WiFi connected)
• LOW POWER: 1-10 mA (idle with optimizations)
• IDLE: 1 µA - 1 mA (deep idle, minimal activity)
• SLEEP/OFF: < 1 µA (suspend/sleep modes)

Data Logging

All measurements are automatically logged to CSV files with format: eink_power_YYYYMMDD_HHMMSS.log

CSV columns:

• timestamp: Full timestamp
• current_A: Raw current in amperes
• power_W: Calculated power in watts
• current_readable: Human-readable current
• power_readable: Human-readable power

Firmware Optimization Workflow

1. Baseline Measurement

Before implementing power optimizations:

ssh michael-laptop
./power_monitor.sh 2 600  # 10-minute baseline

2. Deploy Optimized Build

Flash new firmware to E-Ink board and restart monitoring:

./power_monitor.sh 2 600  # 10-minute optimized measurement

3. Comparative Analysis

Compare log files to quantify power reduction:

• Target: 50-80% power reduction
• Goal: 5-year battery life capability
• Baseline: Previous build measurements
• Optimized: Current build measurements

4. Power State Analysis

Monitor different operational states:

• Boot sequence: Power consumption during startup
• WiFi connection: Network initialization power
• Idle state: Background power consumption
• E-Ink update: Display refresh power usage
• Sleep mode: Suspend/resume power levels

Manual SCPI Commands

For advanced debugging, direct SCPI commands can be sent:

# Get device identification
echo '*IDN?' | nc -w 5 192.168.1.116 5025

# Get current reading
echo 'READ?' | nc -w 5 192.168.1.116 5025

# Check measurement configuration
echo 'CONF?' | nc -w 5 192.168.1.116 5025

# Set measurement range (if needed)
echo 'CONF:CURR 0.1' | nc -w 5 192.168.1.116 5025

Power Optimization Targets

Current Measurements (Build 2097)

• Baseline: ~10 nA (very low, possibly sleep mode)
• Expected Active: 10-100 mA depending on activity
• Target Reduction: 50-80% from baseline active power

Battery Life Estimation

For 5Ah battery capacity:

• Current draw: Measured average current
• Battery life: 5Ah / average_current_A = hours
• Target: 5+ years (43,800+ hours)
• Required: < 114 µA average current

Key Optimization Areas

1. CPU Frequency Scaling: 30-50% reduction potential
2. WiFi Power Management: 15-25% reduction potential
3. Filesystem Optimizations: 10-20% reduction potential
4. Service Optimizations: 5-10% reduction potential

Troubleshooting

Connection Issues

# Test meter connectivity
ping 192.168.1.116

# Test SCPI interface
echo '*IDN?' | nc -w 5 192.168.1.116 5025

Measurement Issues

• Very low readings (nA): Board may be in sleep mode or disconnected
• No readings: Check meter configuration and connections
• Erratic readings: Verify stable power supply and connections

Script Issues

• Python errors: Ensure python3 is available on monitoring laptop
• Network timeouts: Check network connectivity to meter
• Permission errors: Ensure script is executable (chmod +x power_monitor.sh)

Integration with Build Process

Automated Testing

Power monitoring can be integrated into the build validation process:

1. Pre-deployment: Baseline measurement of current build
2. Post-deployment: Optimized measurement of new build
3. Validation: Automatic comparison and reporting
4. Decision: GO/NO-GO based on power reduction targets

Continuous Monitoring

For long-term validation:

# 24-hour continuous monitoring
./power_monitor.sh 60 1440  # 1-minute intervals for 24 hours

This enables validation of:

• Power consumption over full operational cycles
• Battery life projections under real usage
• Thermal stability and power efficiency
• Sleep/wake cycle optimization

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Last Updated: October 4, 2025
Build Context: Build 2098 power optimization validation
Target: 5-year battery life achievement through 50-80% power reduction