ELS - Electronic Leadscrew Module

Smoothieware V2 Only: The ELS module is only available in Smoothieware V2. It is not supported on Smoothieboard V1 hardware.

Work in progress: The Fall 2026 announcement and current source both treat this interface as experimental. Button S3 still uses a fixed 20 mm move, and the underlying direct-synchronization path has the limits documented on the Lathe page.

The ELS (Electronic Leadscrew) module provides a user-friendly interface for lathe operations, inspired by projects like the Clough42 Electronic Leadscrew. It combines the Lathe module with a TM1638 display to create a standalone lathe control interface.

Overview

The ELS module provides:

Real-time RPM display on a 7-segment LED display
Pitch/feed rate selection using physical buttons
Visual status indicators via LEDs
Standalone operation without requiring a host computer

This makes it ideal for manual lathe operations where you want the convenience of electronic leadscrew control without needing to use a computer interface.

Hardware Requirements

The ELS module requires:

TM1638 Display Module - 8-digit 7-segment display with 8 LEDs and 8 buttons
Lathe Module - Spindle encoder and threading support
Spindle Encoder - Quadrature encoder for RPM and position feedback

TM1638 Display

The TM1638 module is a common, inexpensive display board that includes:

8 seven-segment digits
8 individual LEDs
8 push buttons

These are widely available from electronics suppliers and provide an excellent interface for lathe control.

Display Layout

┌─────────────────────────────────────┐
│  [LED1] [LED2] [LED3] ... [LED8]    │
│                                     │
│  ████  ████  ████  ████  ████ ...   │
│   RPM Display    │  Pitch/Feed     │
│                                     │
│  [S1] [S2] [S3] [S4] [S5] [S6] [S7] [S8]
└─────────────────────────────────────┘

Display Areas

Digits	Content
1-4 (left)	Current spindle RPM
5-8 (right)	Selected pitch/feed value

LED Indicators

LED	Meaning when ON
LED 1	Lathe operation is running
LED 2	Distance mode (G33 Z specified)
LED 3	Reversed direction
LED 4	Unused
LED 5-8	Selected digit while editing the pitch

Button Functions

Button	Function
S1	Stop current operation
S2	Start manual direct synchronization with `G33.1 K{pitch}`
S3	Start `G33.1 K{pitch} Z20`; the 20 mm distance is currently hard-coded
S4	Enter pitch-edit mode, advance through its four digits, then finish editing
S6	Decrease the selected digit while editing, or decrease the value by 0.1 mm/rev outside edit mode
S8	Increase the selected digit while editing, or increase the value by 0.1 mm/rev outside edit mode
S5, S7	No implemented action in the current source

Configuration

Enable ELS Module

[els]
enable = true

Complete Setup

The ELS module requires both the Lathe and TM1638 modules to be configured:

# Lathe module configuration
[lathe]
enable = true
encoder_ppr = 1000
use_qe = true
qe_pullup = false
index_pin = PD15-
index_edge = rising

# TM1638 display configuration
[tm1638]
enable = true
clock_pin = PJ11
data_pin = PJ6
strobe_pin = PJ9

# ELS module configuration
[els]
enable = true

Configuration Options

Section	Option	Description	Default
`[els]`	`enable`	Enable the ELS module	`false`

The ELS module automatically discovers and uses the configured Lathe and TM1638 modules.

Operation

Basic Usage

Power on - Display shows current RPM (left) and pitch value (right)
Adjust pitch - Use S8 and S6 for 0.1 mm/rev changes, or use S4 to edit one of the four digits
Start spindle - Use your spindle control (M3 command or physical switch)
Engage leadscrew - Press S2 to start synchronized motion
Stop - Press S1 to disengage

Manual electronic leadscrew workflow

Set up your workpiece and tool
Adjust the pitch value on the display (e.g., 1.5 for 1.5mm pitch thread)
Start the spindle at appropriate RPM
Position the tool at the thread start position
Press S2 to engage the electronic leadscrew
The carriage follows the spindle quadrature encoder without a preset distance
Press S1 to stop when threading is complete

Manual Mode vs Distance Mode

Manual mode: Press S2 to issue G33.1 K...; press S1 to send its stop request.
Fixed test move: S3 issues G33.1 K... Z20. The direction and distance are not configurable in the current ELS interface, so do not treat this as a finished threading cycle.
Command-line distance mode: Issue a supported G33 or G33.1 form directly, following the distinctions and limits on the Lathe page.

LED 2 indicates whether distance mode is active (specified via G-code).

Troubleshooting

Display Shows Nothing

Verify TM1638 wiring (clock, data, strobe pins)
Check TM1638 module is enabled in configuration
Ensure power supply to TM1638 module

RPM Shows Zero

Verify spindle encoder is connected and working
Check Lathe module configuration (encoder_ppr)
Ensure spindle is actually rotating

S2 button does not start synchronization

Spindle must be running (RPM > 0)
Lathe module must be properly configured
Check for error messages in console

Display is Garbled

Check for loose wiring connections
Verify pin assignments in configuration
Try reducing the display update rate (requires source modification)

Lathe Module - Core lathe threading functionality
TM1638 Display - Display hardware interface
Button Box - Alternative button panel interface