PAC193X

<examples/I2C/Wire/PAC193X>

PAC193x Energy Monitor

Overview

This application demonstrates the use of the PAC193x Energy Monitor IC used onboard the SOMRT1061 development platform. The PAC193x is a multi-channel power/energy monitor that provides accurate measurements of voltage, current, power, and energy consumption.

Hardware Requirements

• SOMRT1061 development board with onboard PAC193x IC
• I2C interface for communication
• 24.9 milliohm sense resistor (default configuration)

Features

The application provides comprehensive power monitoring capabilities including:

• Voltage Monitoring: Bus voltage measurements in millivolts
• Current Sensing: Current measurements in milliamps through sense resistor
• Power Calculation: Instantaneous and average power in milliwatts
• Energy Tracking: Energy consumption in milliwatt-hours
• Device Identification: Product ID, Manufacturer ID, and Revision ID readout

Application Flow

1. Initialization
   • Initialize I2C communication
   • Configure PAC193x with default settings
   • Read and display device identification information
2. Continuous Monitoring
   • Updates all measurement values every 4 seconds
   • Displays comprehensive power statistics
   • Shows system tick counter for timing reference

Configuration Details

Default Settings

• I2C Address: 0x10
• Sense Resistor: 24.9 milliohms
• Sample Rate: Configurable (8, 64, 256, or 1024 samples/second)
• Channels: Channel 1 active, channels 2-4 disabled
• Update Interval: 4 seconds

Register Configuration

• NEG_PWR register: 0x00 (no negative power detection)
• CTRL register: 0x02 (control settings)
• CHANNEL_DIS register: 0x70 (disable channels 2-4)
• SLOW register: 0x20 (timing configuration)

Measurement Output

The application displays the following measurements:

Product      ID: 0x##
Manufacturer ID: 0x##
Revision     ID: 0x##
 
Read start:
Voltage    (mV) = ###.######
Vsense     (mV) = #.######
Current    (mA) = #.######
Raw Power (HEX) = 0x########
Power      (mW) = #.######
Avg Power  (mW) = #.######
Raw Power Acc   = 0x################
Acc Count       = 0x########
Energy    (mWh) = #.######

Key Functions

Setup Functions

• SetupPwrMon(): Initializes I2C and PAC193x, reads device IDs
• pwrMon.begin(): Configures PAC193x registers and performs initial refresh

Measurement Functions

• UpdateVoltage(): Reads bus voltage
• UpdateVsense(): Reads sense voltage across resistor
• UpdateCurrent(): Calculates current from sense voltage
• UpdatePower(): Calculates instantaneous power
• UpdateAvgPower(): Calculates average power from accumulator
• UpdateEnergy(): Calculates energy consumption

Error Handling

The library includes comprehensive error handling with the following error codes:

• 0: No error
• -1: I2C read communication error
• -2: I2C write communication error
• -3: Invalid sense resistor value (zero or negative)
• -4: Invalid sample rate selection

Technical Specifications

Voltage Measurement

• Range: 0-32V
• Resolution: 16-bit
• LSB: 32000mV / 65536 = ~0.488mV

Current Measurement

• Method: Sense voltage across precision resistor
• Sense Voltage Range: +/-100mV
• Resolution: 16-bit
• Calculation: Current = (Vsense / Rsense) * 1,000,000 uA

Power Measurement

• Method: Digital multiplication of voltage and current
• Resolution: 28-bit
• Accumulation: 48-bit accumulator for average calculations

Library Architecture

The PAC193x library provides both raw register access and calculated real-world values:

• Raw Functions: Direct register values for maximum precision
• Calculated Functions: Converted values in standard engineering units
• Flexible Configuration: Multiple constructor options for different setups
• I2C Abstraction: Compatible with standard Wire library interface

Usage Example

#include "PAC193x.h"
 
PAC193x pwrMon(Wire, 100000);  // Use Wire interface with 100k I2C speed
 
void setup() {
    Wire.begin();
    pwrMon.begin();
    
    // Read device information
    pwrMon.UpdateProductID();
    pwrMon.UpdateManufacturerID();
    pwrMon.UpdateRevisionID();
}
 
void loop() {
    // Update all measurements
    pwrMon.UpdateVoltage();
    pwrMon.UpdateCurrent();
    pwrMon.UpdatePower();
    pwrMon.UpdateEnergy();
    
    // Access measured values
    float voltage = pwrMon.Voltage;    // mV
    float current = pwrMon.Current;    // mA
    double power = pwrMon.Power;       // mW
    float energy = pwrMon.Energy;      // mWh
    
    delay(1000);
}

File Structure

• main.cpp: Main application demonstrating PAC193x usage
• PAC193x.h: Library header with class definition and register addresses
• PAC193x.cpp: Library implementation with all measurement functions