SCE2

Small 4 axis stepper motor controller module with g-code interpretator

Overview

SCE2-M is a fully integrated stepper motor controller module for digital control for limited space applications. Designed for small 3D printers, laser cutters/engravers, CNC mills, pick and place machines, robots, test fixtures, and other motorized devices. SCE2-M module is the smallest motor controller that requires no external components and runs industry-standard g-code processor with linear interpolation control open-source firmware

IMG_2828_r_rot.jpg

Features

Pinout

SCE2-M module has some STM32 pins routed to external pads. Pads grouped by functionality provided in tables below.

Pinout

SCE2-M_diagram_w1.png

GPIO pin mapping table
IO pin CPU port Function CPU features
1 PB1 SPINDLE ENABLE ADC
2 PB9 PROBE I2C SDA
3 PA8 PWM OUTPUT  
4 PB4 FLOOD  
5 PB3 MIST  
6 PB0 SPINDLE DIR ADC
7 PB5 STOP  
8 PB8   I2C SCL

PA8 (PWM OUTPUT) is set to 10kHz frequency, but can be adjusted in firmware.

Limit switch mapping table
Port Net name
PB12 LIMIT1
PB13 LIMIT2
PB14 LIMIT3
PB15 LIMIT4
PA9 LIMIT_EN
UART pin mapping table
CPU port Net name
PB7 USART1_RX
PB6 USART1_TX
Schematic symbol

Sce2-m3.png

5V is used for motor drivers. Logic level of all GPIO pins is 3.3V

Dimensions and footprint

Mechanical dimensions

SCE2-M_2_dim1.png

Component footprint

sce2-m_footprint.png

3D STEP file is maintained on Github

Firmware

Connectivity

Firmware update can be done over SWD interface with an inexpensive programmer.

1. If possible disconnect the lens from the controller.

2. Connect programmer to the controller.

ST-LINK/V2 signal (pin) Controller signal
VAPP (1,2) VAPP (3.3-5V)
GND (20) GND
TRST (3) RST
TMS_SWDIO (7) IO
TCK_SWCLK (9) CLK

3. Connect power supply to the controller.

IMG_7221_r.jpg

Firmware update

Before updating firmware, read GRBL parameters! Use tools to automate the process.

We recommend using original ST-LINK/V2, STLINK-V3SET or STLINK-V3MINI programmer. Download STLINK-UTILITY software from ST, open firmware file and program the microcontroller.

stlink-utility.png

After the firmware update, internal EEPROM content is erased. Lens settings should be updated. Do not connect the lens before restoring settings! Reference parameters and tools for can be found here

Firmware revisions

Binary firmware files can be downloaded from the SCE2-SDK Github repository.

Version Date Changes
1.1f-SCE2 2022-01-19

Initial public release version
1.1g-SCE2 2022-08-21

Fixed axis homing issue

 

Communication over USB

Drivers

Stock firmware registers as "STM32 Virtual COM". Most modern operating systems should work out of the box, but original drivers can be downloaded from STMicroelectronics web page

COM port

Firmware is configured to work at 115200 8N1 baud rate

Terminal program

Feel free to use favorite terminal program. For further demonstration will use Terminal App

terminal.png

In some Windows cases Prolific USB to serial controller drivers can claim detected COM port, in this case uninstall driver and install downloaded from ST web page.

 

Quick start guide

First motor moves

Assume axis has proper configuration sent earlier, making moves is as easy as entering command

In terminal bottom field type G0 X10 and press Enter

terminal_1.png

If linear actuator is connected it should move at default max speed by 10mm (rotary actuator should turn 10deg).

In order to move at different speeds G1 command should be used. For example G1 Y10 F100

List of supported G-code commands:

Controller is shipped with X axis configured for RSB1 and X axis configured for LSA1 (0.635mm version)

Configuration

In order for controller to function correctly pulse count per revolution, acceleration and optionally motion limits has to be specified. In order to read configuration type $$ and press Enter.

Read configuration parameters

All internal configuration parameters will be printed out. For example:

$0=6
$1=255
$2=0
$3=31
$4=1
$5=0
$6=0
$10=19
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=15
$24=50.000
$25=200.000
$26=250
$27=5.000
$30=1000
$31=0
$32=0
$100=111.110
$101=1007.874
$102=17.778
$103=1536.000
$110=20000.000
$111=2500.000
$112=500000.000
$113=20000.000
$120=2000.000
$121=300.000
$122=40000.000
$123=1000.000
$130=360.000
$131=90.000
$132=360.000
$133=360.000

Detailed explanation can be found on GRBL documentation

Write configuration parameters

Writing specific value is as easy as typing $100=1000 and pressing Enter If number is valid, this command will overwrite existing value and save to EEPROM.

Control software

There are number of software packages suited to control CNC machines. Comprehensive list is maintained by GRBL developers on GitHub. Our favorite is Candle by Denvi

screenshot_heightmap_original.png

Some g-code examples and recipes

G-code while being universal machine control language has various flavors and capabilities. Below section is dedicated to speed up manual machine control with simple commands.

Move motors

There are two basic linear motion commands G0 and G1. Both are generally the same just G0 uses default max speed constant from configuration. Examples (assume linear actuator is connected):

Command Explanation
G0 X100 Move X axis to absolute position 100mm
G1 X0 F100 Move X axis to 0 position at speed 100mm/min

Control GPIO pins

GRBL is designed for CNC machines and IO pins are used to make sense. Pin description is provided here, but for actual functionality source code should be inspected.

Command Explanation
M7 MIST = ON
M8 FLOOD = ON
M9 MIST = OFF, FLOOD = OFF
Command Explanation
M3 Set clockwise spindle rotation
S300 Set spindle control pin PWM duty cycle at 30% (max S = 1000)
M4 Set counter clockwise spindle rotation
M5 Turn spindle off

Motor homing

After powering controller on it does not know motor position, thus it should be driven to home reference position

Command Explanation
$HX Initialize X axis

Read controller status

Almost any time controller status can be read with command ?. It will report motor status (Idle/Run), actual positions and some other info.

Command Output
? <Idle|MPos:0.000,90.000,0.000,0.000|Bf:35,254|FS:0,0>

Read firmware version string

Functionality between versions will vary, some firmware versions or branches can have special functionality.

Command Output
$I [VER:1.1f-SCE2.20200405:]
[OPT:VMZHL,35,254]
ok

Probing

Firmware allows use of touch trigger probes. Moves down Z axis and stops on when probe pin is triggered, then reports collision point.

Command Explanation and Output
G38.2 F100 Z-100

Move down Z axis until PROBE pin is triggered

  • F - Speed
  • Z - Target depth

Replies with [PRB:1.503,0.000,-22.860,0.000:1]

Idle / wait

Idle command is useful for certain operations where controller needs to wait and do nothing (for example wait till spindle speeds up).

Command Explanation
G4 P1.5 Wait 1.5 seconds, reply with ok when done

Read write parameters

Controller has quite a few parameters that can be set in EEPROM. See original description here.

Command Explanation and Output
$$

Read parameters

 

$0=6
$1=255
$2=0
$3=31

...
$132=360.000
$133=360.000
ok

 
$132=100.00

Set single paramter with the new value

 

Replies with ok

Extra commands

Extra GPIO control commands used in motorized zoom lenses (L084, L0117, ...).

Command Explanation and Output
M113 Px Control GPIO IO3, replies with ok
M114 Px Control GPIO IO4, replies with ok
M115 Px Control GPIO IO5, replies with ok
M116 Px Control GPIO IO6, replies with ok
M117 Px Control GPIO IO7, replies with ok
M120 Px Control GPIO LIM_EN, replies with ok

Where X is 0 or 1

Reading and writing TMC2300 registers

Firmware has implemented functionality to read and write individual Trinamic TMC2300 registers over internal UART single wire interface. It shares transmit and receive line like an RS485 based interface. Data transmission is secured using a cyclic redundancy check and each TMC2300 driver is addressed individually as follows:

Axis Address
X 0
Y 1
Z 2
A 3
Broadcast to all axes 9

Official TMC2300 documentation

All numbers in g-code arguments are decimal base numbers

Write registers

Write register command forwards g-command arguments to TMC2300 configuration interface. While it is not recommended because of stability issues, write command can be sent even if motors are turning (G0, G1, ... commands)

7'th bit of TMC2300 register has to be set to 1, thus for example 0x10 IHOLD_IRUN becomes 0x90

G100 P<xx> L<xx> N<xx> S<xx> F<xx> R<xx>
G-command TMC2300 address TMC2300 register (mask with 0x80) DATA3 DATA2 DATA1 DATA0

tmc2300_write2.png

Required checksum is calculated in firmware

Read registers

Read registers command has two arguments TMC2300 address and register address. It responds to terminal immediately.

G101 P<xx> R<xx>
G-command TMC2300 address TMC2300 register

Response is decimal coded 12 bytes. Sample reply looks like this: [TMC:5,0,16,112,5,255,16,0,0,0,0,157]

Reply byte Meaning
0 Echo transmit byte0
1 Echo transmit byte0
2 Echo transmit byte0
3 Echo transmit byte0
4 Reply from TMC2300 sync (0x05)
5 Address
6 Register
7 Data byte3
8 Data byte2
9 Data byte1
10 Data byte0
11 Checksum

tmc2300_read2.png

Examples

Set motor X current

Each motor driver can drive different motor. Power and other settings can be set individually. For example IHOLD_IRUN (0x10) register controls motor idle, run and timing parameters.

G100 P0 L144 N0 S0 F10 R5

G100 Write to TMC2300 g-command
P0

Driver address = 0 (X axis)
L144

TMC2300 register IHOLD_IRUN (0x10)

0x10 ->(set 7'th bit to 1)-> 0x90 = 144 (dec)
N0 Data3 = 0 (not used)
S0 Data2 = 0 (see IHOLDDELAY in table below)

F10

 Data1 = 10 (see IRUN in table below)
R5 Data0 = 5 (see IHOLD in table below)

tmc2300_pwr_registers2.png

Read input register

Each TMC2300 driver has input status registers GSTAT (0x01) indicating over temperature, short circuit, and more.

G101 P0 R1

Response looks like:

[TMC:5,0,1,193,5,255,1,0,0,0,1,154]

Response contains only 3 bits of useful information. See explanation in table below.

tmc2300_status.png

Automating tasks

Python g-code sender

Automating tasks can be done with Python script. Below is script example to send commands provided in text file:

import time
import os
from tqdm import tqdm
import serial
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('-p','--port', help='COM port', required=True)
parser.add_argument('-f','--file', help='File name', required=True)
args = parser.parse_args()

ser = serial.Serial()
ser.port = str(args.port)
ser.baudrate = 115200
ser.timeout = 10
ser.open()
ser.flushInput()
ser.flushOutput()

print("Reading file...")
lines = []
with open(args.file) as fp:
   for cnt, line in enumerate(fp):
       lines.append(line)

print("Sleeping 1s...")
time.sleep(1)

for line in tqdm(lines):
    l = bytes(line.strip()+ '\n', 'utf8')
    ser.write(l)
    grbl_out = ser.readline()

Text file example:

G91

M7

M8
G1 X45 F20000
M9
G1 X45 F20000

M8
G1 X45 F20000
M9
G1 X45 F20000

M8
G1 X45 F20000
M9
G1 X45 F20000

M8
G1 X45 F20000
M9
G1 X45 F20000

G90

 

SCE2-BREAKOUT demo board

SCE2-BREAKOUT is a fully integrated stepper motor controller module carrier board for quick SCE2-M module evaluation. Designed for small 3D printers, laser cutters/engravers, CNC mills, pick and place machines, robots, test fixtures, and other motorized devices. SCE2-M module is the smallest motor controller that requires no external components and runs industry-standard g-code processor with linear interpolation control open-source firmware. Kurokesu-SCE2-breakout-1-1000x800.jpg

Schematics

SchematicPrints.png

P9 is breaks power supply from USB port. Should be disconnected if power is applied via P8 header

P10 bridges 5V and VM. Should be disconnected if VM is applied via P8

Dimensions

zc2SCE2_BREAKOUT.png

3D STEP file is maintained on Github

 

SCE2_dual_L012 dual lens controller board

SCE2_dual_L012 is a fully integrated stepper motor controller module carrier board for controlling two motorized lens zoom/focus parameters. Controller requires only 5V power supply from the USB port and controlled with text-based G-code commands over USB or optionally TTL UART.

IMG_2458_r.jpg

Schematics

SCE2_dual_L012.png

Motor wiring vs axis definition

Axis Motor function Connector
X Focus J1
Y Zoom J1
Z Focus J2
A Zoom J2

Controlling the lenses

Controller is shipped with default settings as listed below.

$0=6
$1=255
$2=0
$3=31
$4=1
$5=0
$6=0
$10=19
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=15
$24=50.000
$25=200.000
$26=250
$27=5.000
$30=1000
$31=0
$32=0
$100=111.110
$101=111.110
$102=111.110
$103=111.110
$110=50000.000
$111=50000.000
$112=50000.000
$113=50000.000
$120=5000.000
$121=5000.000
$122=5000.000
$123=5000.000
$130=360.000
$131=360.000
$132=360.000
$133=360.000
$N0=G100P9L144N0S0F1R1
Startup sequence

Default TMC2300 power is too high for small stepper motors and will overheat and damage them. Motor drive/sleep current has to be decreased with commands listed below:

G100 P0 L144 N0 S0 F1 R1
G100 P1 L144 N0 S0 F1 R1
G100 P2 L144 N0 S0 F1 R1
G100 P3 L144 N0 S0 F1 R1

Or in a single command (valid since 20200103 firmware update)

G100 P9 L144 N0 S0 F1 R1

Which then can be added in GRBL startup sequence $N0=G100P9L144N0S0F1R1

Homing sequence

Lenses have no limit switches, thus precision homing is not possible. Instead each motor is driven to max position until hard stop and it is assumed that home position is achieved.

G91 # set motion to relative coordinate system
F30000 # set default motion speed
G1 X-500 
G1 Y-1200
G1 Z-500 
G1 A-1200
G90 # set motion to absolute coordinate system
G92 X0 Y0 Z0 A0 # set current position as 0
Control sequence

If power settings are reduced in startup stage, lens motors can be operated right away. Standard G-code motion commands can be used to drive motors. For example:

G1 Y100 A100 F40000
G1 Y-100 A100 F40000
G1 Y100 A-100 F40000
G1 Y-100 A-100 F10000
 

Dimensions

V3ISCE2_dual_L012.png

Mounting hole diameter is (not indicated) in drawing is 2.3mm

3D STEP file is maintained on Github

 

Precautions and disclaimers

General disclaimer

Precautions