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emon32 Serial Commands Reference

This document lists all available serial commands for the emon32 firmware (emonPi3/emonTx6).

Serial Connection Settings

USB CDC (Virtual Serial Port)

  • Baud rate: Not applicable (USB CDC automatically negotiates)
  • Data format: 8 data bits, no parity, 1 stop bit (8N1)
  • Line termination: \r\n or \n
  • Flow control: Not required (optional on Windows for some terminal applications)

Hardware UART

  • Baud rate: 115200
  • Data format: 8 data bits, no parity, 1 stop bit (8N1)
  • Line termination: \r\n or \n
  • Flow control: Not used

Quick Start

To test if your serial connection is working, try these commands first:

  • v - Shows firmware version and board info
  • l - Lists all current configuration settings
  • t - Triggers an immediate data report
  • ? - Shows the built-in help text

Command Reference

Command Description
? Show help text
a<n> Set the assumed RMS voltage as integer (when no AC voltage detected)
Example: a230 sets assumed voltage to 230V
b Backup configuration to serial
c<n> Log to serial output
- c0: Disable serial logging
- c1: Enable serial logging
d<x.x> Set data log period in seconds
Example: d10.0 sets logging period to 10 seconds
e Enter bootloader mode for firmware updates
f<n> Set line frequency in Hz
- f50: 50 Hz (Europe, UK, etc.)
- f60: 60 Hz (US, Canada, etc.)
g<n> Set network group for RF communication (default = 210)
Example: g210
j<n> JSON serial format
- j0: Disable JSON format
- j1: Enable JSON format
k<x> <a> <y.y> <z.z> <v1> <v2> Configure an analog input (voltage or current)
Parameters:
- x: Channel number (1-3 = Voltage; 4+ = CT)
- a: Active status (0 = DISABLED, 1 = ENABLED)
- y.y: V/CT calibration constant
- z.z: CT phase calibration value (degrees)
- v1: CT voltage channel 1 (reference)
- v2: CT voltage channel 2 (for L-L loads)
Example: k4 1 90.0 1.5 1 1
l List current settings (displays all configuration)
m<v> <w> <x> <y> <z> Configure a OneWire/pulse input
Parameters:
- v: Channel index
- w: Active status (0 = DISABLED, 1 = ENABLED)
- x: Function select
  - b: Both edges (pulse)
  - f: Falling edge (pulse)
  - r: Rising edge (pulse)
  - o: OneWire (temperature sensor)
- y: Pull-up resistor (0 = OFF, 1 = ON)
- z: Minimum time, in milliseconds, between pulses
Example: m1 1 r 1 50
n<n> Set node ID [1..60]
Example: n5 sets node ID to 5
o OneWire configuration
Options:
- x = ca: clear all saved OneWire addresses
- x = c<n>: clear saved OneWire address for channel n
- x = f: reset and find OneWire devices
- x = h: hold the found OneWire addresses (overrides any manually configured addresses)
- x = l: list OneWire devices
- x = n: list all saved OneWire addresses
- x = integer, n: move an address to position n (see Examples)
- x = r <a> <b>, remap found sensor <a> to index <b>
p<n> Set the RF power level
Example: p7
q Reset the system (confirmation required)
r Restore default settings (unsaved changes will be lost)
rs Restore saved settings (unsaved changes will be lost)
s Save settings to NVM (non-volatile memory)
Must be used after making configuration changes
t Trigger report on next cycle (force immediate data transmission)
v Show firmware and board information
w<n> RF module active
- w0: Disable RF
- w1: Enable RF
x<n> 433 MHz RF frequency compatibility
- x0: 433.92 MHz (standard)
- x1: 433.00 MHz (legacy compatibility)
z Zero energy/pulse accumulators (reset Wh/pulse counters)
- z: Zero all accumulators (E1-E12, pulse1-3) with confirmation
- ze1 to ze12: Zero individual energy accumulator (e.g., ze3 zeros E3 only)
- zp1 to zp2: Zero individual pulse accumulator (e.g., zp1 zeros pulse1 only)
All commands require 'y' confirmation

Configuration Workflow

When making configuration changes:

  1. Make your changes using the appropriate commands (e.g., k, m, f, etc.)
  2. Verify with l (list settings)
  3. Save with s (save to NVM)

Examples

Enable Voltage Channels V2 and V3 (for 3-phase monitoring)

k2 1 100.0           # Enable V2 with default calibration (100.0)
k3 1 100.0           # Enable V3 with default calibration (100.0)
s                    # Save configuration

Note: For voltage channels (1-3), you only need:

  • Channel number (2 or 3)
  • Active status (1 = enabled)
  • Calibration value (typically 100.0, range: 25.0-150.0)

The phase and voltage reference parameters (v1, v2) are only required for CT channels.

Configure a CT channel

k4 1 90.0 1.5 1 1    # Enable CT4, cal=90.0, phase=1.5°, refs V1-V1
s                    # Save configuration

Configure a 3-phase CT on L1-L2

k4 1 90.0 4.2 1 2    # Enable CT4, references V1 and V2 (L1-L2 load)
s                    # Save configuration

Configure a pulse input

These settings are suitable for the OpenEnergyMonitor pulse counter.

m1 1 r 0 0          # Enable OPA1, rising edge, weak pull down, no debounce
s                   # Save configuration

Configure a OneWire input

m2 1 o               # Enable OPA2 for OneWire, pull-up always on
s                    # Save configuration

Enable serial logging with JSON

c1                    # Enable serial logging
j1                    # Enable JSON format
s                     # Save configuration

Set line frequency to 50 Hz

f50                   # Set to 50 Hz
s                     # Save (will automatically reset)

Save a OneWire temperature sensor to a position

OneWire temperature sensors such as the DS18B20 are found in order. If a temperature sensor is removed, then the index of the remaining sensors will change. To save a sensor to an index so it is always shown there, use the following steps. In this example, the temperature sensor's 64 bit address is 0xea3ce104577b0728 and it is saved to index 3.

ol                         # List the sensor addresses (optional)
o3 28 7 7b 57 4 e1 3c ea   # Save address to index 3
s                          # Save (no reset)

Note

For DS18B20 temperature sensors, the first byte is always 0x28.

Zero accumulator counters

z                     # Zero all accumulators (requires 'y' confirmation)
ze3                   # Zero only E3 accumulator (requires 'y' confirmation)
zp1                   # Zero only pulse1 accumulator (requires 'y' confirmation)

Note

Individual accumulator reset reads current values from NVM, zeros the specified accumulator, and writes back. The runtime counter continues from zero for that accumulator.

Troubleshooting

No Output on USB CDC

If you're not seeing any output on USB:

  1. Check that your serial terminal is connected (COM port open)
  2. On Windows, some terminal applications may require DTR/RTS flow control enabled
  3. Try sending v to request board information
  4. Try sending t to trigger an immediate data report
  5. Try sending l to list configuration
  6. Check if serial logging is enabled with c1 then s

No Output on Hardware UART

If you're not seeing any output on the hardware UART:

  1. Verify the UART configuration: 115200 baud, 8N1
  2. Check Rx/Tx connections - ensure they are the correct way around:
    • Board TX → Your device RX
    • Board RX → Your device TX
  3. Try sending v to request board information
  4. Verify the cable is properly connected and not loose
  5. Check if serial logging is enabled with c1 then s

Notes

  • Commands are case-sensitive (lowercase only)
  • Line termination: Either \r\n or \n is accepted
  • USB CDC baud rate doesn't matter (automatically negotiated)
  • Hardware UART uses 115200 baud, 8N1
  • Configuration changes are only temporary until saved with s
  • Settings that require a reset will automatically trigger a reset when saved