USB interface

The SMD3 appears as a virtual COM port when plugged into a PC. Configuration and control may be performed via the provided SMD3 software, your own application or any terminal program.

This section is only relevant if you are using terminal software or writing your own application. The provided SMD3 software interacts with the SMD3 in the same way and requires no specialist knowledge to use. A C# API is also provided, allowing you to easily integrate communication with the SMD3 into your own C# .NET application. This is available from our website, at https://arunmicro.com/products/smd3-stepper-motor-drive/.

Configuration

The SMD3 uses a USB Type-C connector, which is both robust and reversible (it may be inserted either way up). The device appears as a virtual COM port on your PC. Configure the serial port as follows:

115200 baud
1 Stop bit
No parity
No flow control

Protocol

A simple text-based protocol is used. Commands are sent to the SMD3, checked and executed, and a response returned. Wait for a response to the previous command before sending the next to avoid buffer overflow in the SMD3. Commands are in the form (Note that angle brackets are shown for clarity only, they are not part of the protocol):

<mnemonic>,<argument 1>,<argument 2>,<argument n>…<CR><LF>

And responses are in the form:

<SFLAGS>,<EFLAGS>,<data 1>,<data 2>,<data n>…<CR><LF>

If the command executed successfully, or:

<SFLAGS>,<EFLAGS>,<error code><CR><LF>

If the command failed to execute correctly.

Where:

Item	Description
<mnemonic>	Short sequence of characters representing a command, case insensitive
<argument n>	Zero or more command arguments
<data n>	Zero or more response data items
<error code>	An error code, see section Error Codes. This includes both a number and text description of the error to aid when using the SMD3 via a terminal program.
<SFLAGS>	Set of flags representing the status of the SMD3, such as the state of the limit inputs or whether the joystick is connected. See section Status Flags
<EFLAGS>	Set of flags representing the error state of the SMD3, such as invalid mnemonic, or motor over-temperature fault. See 0
<CR><LF>	Message terminator; carriage return followed by line-feed (0x07,0x0D)

Comma separation
All elements are comma-separated, except for the message terminator which immediately follows the last item. A response is always sent on receipt of a message terminator. If an argument was supplied with a command, for example, to set a value, the value set will be returned in the response and serves as an additional confirmation of the command having executed as expected.

Many commands accept a real number argument when the underlying quantity is an integer, or finite set of real numbers. In this case, the supplied value being otherwise acceptable is rounded to the closest integer or real number from the allowed set, and it is this value that is returned in the response.

White space
Additional white space (tabs and spaces) are ignored except where they are surrounded by characters comprising the data item, in which case they will be considered as part of the data item itself.

No data items to return
If there are no data items as part of a response, only the SFLAGS and EFLAGS are returned. If an error occurred, then this will be reflected in the EFLAGS.

Argument types

Arguments may be one or a mix of the following types, depending on the command. Data returned by the SMD3 uses the same types, which are always presented as indicated in the “SMD3 response” column.

Type	Name	Description	Example argument values	SMD3 response
INT	Integer	Integer value, with or without sign	100, -10, +7	Sign included for negative values only. E.g. 100, -10
UINT	Unsigned integer	Unsigned integer value, no sign. Hexadecimal representation may also be used, case insensitive	99, 1000, 0xA74F, 0xd7	Numeric format E.g. 100, 200 Except for status and error flags which are returned in upper case 2-byte hexadecimal format, E.g. 0x1234, 0xA4DE
FLOAT	Real number	Real number, with or without sign. Scientific format may also be used, case insensitive	10.23, 100e-3, 100E4, 10	Scientific format, with 5 places after the decimal point and a 2-digit exponent E.g. 1.23000E+04, 5.76159E-10
STRING	ASCII string	ASCII string, consisting of characters 0x20 to 0x7E inclusive	Abc123 78-%^A	ASCII string, E.g. “1234 abc”, “10%”
BOOL	Boolean	Binary, true/false value	0, 1	E.g. 0, 1

Flags

Error flags are reported by the SMD3 in hexadecimal format as explained above. E.g. a value of 0x0002 means bit 1 is set (TOPEN), indicating that the SMD3 has been disabled due to an open circuit temperature sensor.

Error flags (EFLAGS)

These indicate error conditions and are latching (i.e. remain set even after the error condition that caused them no longer persists). Clear using the CLR command or by using the reset fault input. The motor is disabled if one or more error flags are set.

Bit	Name	Description
0	TSHORT	Selected temperature sensor is short-circuited (Not applicable to Thermocouple)
1	TOPEN	Selected temperature sensor is open circuit
2	TOVR	Selected temperature sensor is reporting temperature > 190 °C and power has been removed from the motor to protect the windings
3	MOTOR SHORT	Motor phase to phase or phase to ground short has been detected
4	EXTERNAL DISABLE	Motor disabled via external input
5	EMERGENCY STOP	Motor disabled via software
6	CONFIGURATION ERROR	Motor configuration is corrupted
7-15	Reserved	Reserved, read as ‘0’

Status flags (SFLAGS)

Bit	Name	Description
0	JSCON	Joystick is connected
1	LIMIT NEGATIVE	Limit input is active (Note that the polarity is configurable, so active can mean high or low signal level)
2	LIMIT POSITIVE
3	EXTEN	External enable input state
4	IDENT	Ident mode is active, green status indicator is flashing to aid in identifying SMD3
5	Reserved	Reserved, read as ‘0’
6	STANDBY	Motor stationary. Check this bit before performing a function that requires the motor to be stopped first, such as changing mode
7	BAKE	Bake mode running
8	ATSPEED	Set when the motor is at target velocity
9-15	Reserved	Reserved, read as ‘0’

Error codes

Error	Description
-1 (Stop motor first)	Several actions, such as changing resolution or operating mode require that the motor is stopped first. Trying to run such a command before the motor has come to a stop and the standby flag in the status register is set will result in this error.
-2 (Argument validation)	An argument supplied to the command is invalid, for example, it is outside the allowable range.
-3 (Unable to get)	The command is write-only, read is not valid. This applies to commands such as RUNV where a read would have no meaning.
-5 (Action failed)	The command failed to execute due to an internal error, for example, the internal flash in which settings are stored has reached the end of life and data cannot be reliably written to it.
-6 (Not possible in mode)	The command is not applicable to this mode, for example, trying to start bake using RUNB when not in bake mode.
-7 (Not possible when motor disabled)	The motor is disabled (due to a fault, or external enable) and the command is one that starts motion, for example RUNV.
-101 (Argument type)	The argument is of the wrong type, for example a non-integer value was given where an integer value was required.
-102 (Argument count)	The argument count is incorrect, either too few or too many arguments have been supplied.

Quick reference

General

Mnemonic	Description	R	W	Arguments
SER	Read the serial number	●
FW	Read the firmware version number	●
CLR	Clear error flags		●
LOAD	Load saved configuration		●
STORE	Store configuration		●
LOADFD	Load factory defaults		●
IDENT	Identify SMD3 by blinking the status indicator		●	BOOL
MODE	Mode of operation	●	●	UINT
JSMODE	Joystick mode	●	●	UINT
AUTOJS	Auto switch to Joystick mode on JS connect	●	●	BOOL
EXTEN	External enable used	●	●	BOOL
FLAGS	Returns ascii table of status and error flag states	●

Command movement

Mnemonic	Description	R	W	Arguments
RUNV	Move motor velocity mode		●	STRING
RUNA	Move motor absolute positioning mode		●	INT
RUNR	Move motor relative positioning mode		●	INT
RUNB	Activate bake mode		●
RUNH	Start home mode procedure		●	STRING
STOP	Bring motor to a stop according to the current profile		●
SSTOP	Stop motor in 1 second on full step position independently of the current motion profile		●
ESTOP	Emergency stop. Stops the motor immediately		●

Motor

Mnemonic	Description	R	W	Arguments
TSEL	Temperature sensor selection, T/C or RTD	●	●	UINT
TMOT	Temperature in °C	●
IR	Run current in amps	●	●	FLOAT
IA	Acceleration current in amps	●	●	FLOAT
IH	Hold current in amps	●	●	FLOAT
PDDEL	Power down delay in milliseconds	●	●	FLOAT
IHD	Power down ramp delay in milliseconds	●	●	FLOAT
F	Freewheel mode	●	●	UINT
RES	Resolution	●	●	UINT

Limit inputs

Mnemonic	Description	R	W	Arguments
L	Global enable	●	●	BOOL
L+	Limit positive (Limit 1) enable	●	●	BOOL
L-	Limit negative (Limit 2) enable	●	●	BOOL
LP+	Limit n polarity (0 for active high, 1 for active low)	●	●	BOOL
LP-	Limit n polarity (0 for active high, 1 for active low)	●	●	BOOL
LP	Limit polarity for both Limit positive (Limit 1) and negative (Limit 2), (0 for active high, 1 for active low)		●	BOOL
LSM	How to stop on limit being triggered	●	●	BOOL

Profile

Mnemonic	Description	R	W	Arguments
AMAX	Acceleration in Hz/s	●	●	FLOAT
DMAX	Deceleration in Hz/s	●	●	FLOAT
VSTART	Start frequency in Hz	●	●	FLOAT
VSTOP	Stop frequency in Hz	●	●	FLOAT
VMAX	Target step frequency in Hz	●	●	FLOAT
VACT	Actual frequency in Hz	●
PACT	Actual position in steps	●	●	FLOAT
PREL	Relative position in steps	●	●	FLOAT
TZW	Time to stop before moving again in seconds	●	●	FLOAT
THIGH	Full step – micro stepping transition	●	●	FLOAT

Step/Direction

Mnemonic	Description	R	W	Arguments
EDGE	Which edges of step input to generate a step on	●	●	UINT
INTERP	Interpolate step input to 256 micro steps	●	●	UINT

Bake

Mnemonic	Description	R	W	Arguments
BAKET	Bake temperature setpoint	●	●	UINT

Command reference

General

IDENT - Blinks status indicator

Set or query enable blinking of that status indicator to aid in identifying the SMD3 among others.

Command:	IDENT, Enable<CR><LF>
Query:	IDENT<CR><LF>

Arguments

Enable

BOOL

The enable state.

[0:	Disable]
1:	Enable

Returns

The enable state, as above.

Examples

Tx: IDENT,1<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

Tx: IDENT<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

// Set ident function on

// Query state of ident function

MODE - Choose mode of operation

Set or query the operating mode. See section Operating Modes for an explanation of each mode.

Command:	MODE, Value<CR><LF>
Query:	MODE<CR><LF>

Arguments

Value

UINT

The operating mode.

0:	Step/direction
1:	Step/direction triggered velocity
[2:	Remote]
3:	Joystick
4:	Bake
5:	Home

Returns

The mode, as above, followed by a space and the name of the mode in brackets.

Remarks

If the motor is moving when attempting to change the mode, a stop motor first error is returned and the mode is unchanged.

Examples

Tx: MODE,2<CR><LF>

Rx: 0x0000,0x0000,2 (Remote)<CR><LF>

Tx: MODE<CR><LF>

Rx: 0x0000,0x0000,1 (Remote)<CR><LF>

// Set mode to remote

// Query state of mode

JSMODE – Joystick mode

Set or query the joystick mode. Choose between single step, which allows precise single steps or continuous rotation, or continuous which requires only a single button press to make the motor move.

Command:	JSMODE, Mode<CR><LF>
Query:	JSMODE<CR><LF>

Arguments

Mode

UINT

The joystick mode.

[0:	Single step]
1:	Continuous

Returns

The mode, as above.

Remarks

Set requires the motor to be in standby, otherwise, a stop motor first error will be returned.

In single step mode, a brief button press (< 0.5 s) will execute one step in that direction, while pressing the button for > 0.5 s will cause the motor to accelerate up to slewing speed and continue to rotate in that direction until the button is released, at which point the motor will decelerate to a stop.

In continuous mode, a brief button press will trigger the motor to accelerate up to slewing speed. A subsequent press of the same button causes it to decelerate to a stop. If, for example, the clockwise button is pressed while the motor is rotating anti-clockwise, the motor will first decelerate to a stop before changing direction.

Examples

Tx: JSMODE,1<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

Tx: JSMODE<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

// Set JSMODE to continuous

// Query state of JSMDOE

AUTOJS – Auto switch to joystick mode

Set or query auto switching to joystick mode. When enabled the SMD3 switches automatically to joystick mode and reverts to the previous mode on disconnection of the joystick.

Command:	AUTOJS, Enable<CR><LF>
Query:	AUTOJS<CR><LF>

Arguments

Enable

BOOL

The enable state.

0:	Disable
[1:	Enable]

Returns

The Enable, as above.

Examples

Tx: AUTOJS,1<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

Tx: AUTOJS<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

// Set AUTOJS on

// Query state of AUTOJS function

EXTEN – External enable used?

Set or query whether the external enable signal should be used.

Command:	EXTEN, Used<CR><LF>
Query:	EXTEN<CR><LF>

Arguments

Used

BOOL

External enable signal.

[0:	False]
1:	True

Returns

True if the external enable signal is used.

Remarks

The external enable input requires a voltage to be applied between SDE COM and EN on the I/O connector which may be inconvenient if you do not wish to use the enable input. In that case, disable the enable input by sending this command with the argument set to false.

Examples

Tx: EXTEN,1<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

Tx: EXTEN<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

// Set EXTEN on

// Query state of EXTEN function

Command movement

RUNV – Run, velocity

Command to move the motor using velocity mode.

Command:

RUNV, Direction <CR><LF>

Arguments

Direction

String

Direction velocity motion.

‘+’:	Positive
‘-’:	Negative

Remarks

Ensure the profile is set.

Examples

Tx: RUNV,+<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

Tx: RUNV,-<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Start velocity mode to the positive direction

// Start velocity mode to the negative direction

RUNA – Run, absolute position

Command to move the motor to an absolute position using the positioning mode.

Command:

RUNA, Absolute <CR><LF>

Arguments

Absolute

INT

Minimum:	-2²³-1
Maximum:	2²³-1

Remarks

Ensure the profile is set.

Examples

Tx: RUNA,1000<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

Tx: RUNA,-1000<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Start absolute positioning mode, move to the step position 1000

// Start absolute positioning mode to the step position -1000

RUNR - Run, relative position

Command to move the motor to a relative position using the positioning mode.

Command:

RUNR, Relative <CR><LF>

Arguments

Relative

INT

Minimum:	-2²³-1
Maximum:	2²³-1

Remarks

Command requires the motor to be in standby, otherwise, a stop motor first error will be returned. Ensure the profile is set.

Examples

Tx: RUNR,2000<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

Tx: RUNR,-2000<CR><LF>

Rx: 0x0000,0x0000,1<CR><LF>

// Start relative positioning mode, move 2000 steps to the positive direction

// Start relative positioning mode, move 2000 steps to the negative direction

RUNB – Run bake

Command to start the bake mode.

Command:

RUNB<CR><LF>

Remarks

Set mode to bake first. To stop the bake mode send the STOP command.

Examples

Tx: RUNB<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

Tx: STOP<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Start bake mode

// Stop bake mode

RUNH – Home to a limit switch

Command to start the home procedure, in which the motor will move in the specified direction until the limit switch for that direction is triggered, at which point a homing procedure is initiated, see section Limits.

Command:

RUN, Direction <CR><LF>

Arguments

Direction

String

Direction velocity motion.

‘+’:	Positive
‘-’:	Negative

Remarks

Ensure the profile is set and the mode is Home mode.

Examples

Tx: RUNH,+<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

Tx: RUNH,-<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Start homing mode to the positive direction

// Start homing mode to the negative direction

STOP – Stop motor

Command motor to stop moving according to the current profile.

Command:

STOP<CR><LF>

Remarks

During the deceleration phase that stops the motor, any modifications to the acceleration or deceleration interrupt the stopping phase. Re-send the command to restart the motor stopping phase.

Examples

Tx: STOP<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Stop the motor

SSTOP – Stop motor in 1 s

Command motor to stop the motion in 1 second.

Command:

SSTOP<CR><LF>

Remarks

This command does not consider the deceleration set in the profile. Instead, it calculates the deceleration required to stop in 1 second, according to the actual velocity. The motor will stop in a full step position. Steps may be lost if the load requires greater than this duration to stop.

Examples

Tx: SSTOP<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Stop the motor in 1 seconds

ESTOP – Emergency stop

Command stops immediately and disables the motor. Note that this should not be relied on as a safety interlock.

Command:

ESTOP<CR><LF>

Remarks

The motor may stop on a fractional step position, but this is irrelevant as motor power is removed and the motor will snap to a full step position. Steps may be lost.

Examples

Tx: ESTOP<CR><LF>

Rx: 0x0000,0x0000<CR><LF>

// Stop the motor immediately

Motor

TSEL – Temperature sensor selection

AML motors can be ordered with a K-Type thermocouple or a PT100 RTD. Select the correct option for your motor.

Command:	TSEL, SensorType<CR><LF>
Query:	TSEL<CR><LF>

Arguments

SensorType

UINT

Motor temperature sensor type.

[0:	Thermocouple]
1:	RTD

Returns

Selected temperature sensor type, as above.

Remarks

The drive will not allow the motor to run unless a functioning temperature sensor is connected to the selected sensor connection; be sure to select the correct type.

Examples

Tx: TSEL,0<CR><LF>

Rx: 0x0000,0x0000,0<CR><LF>

Tx: TSEL<CR><LF>

Rx: 0x0000,0x0000,0<CR><LF>

// Select thermocouple sensor

// Queue the state of temperature sensor

TMOT – Motor temperature

Query the motor temperature.

Query:

TMOT<CR><LF>

Returns

Motor temperature in °C, rounded to the nearest 1 °C.

Remarks

The reported temperature is intended only for the purposes of monitoring motor temperature and should not be relied upon for any other purpose within the vacuum system.

Examples

Tx: TMOT<CR><LF>

Rx: 0x0000,0x0000,25<CR><LF>

// Query motor temperature

// Response is 25 degree Celsius

IR – Run current

Set or query the motor run current.

Command:	IR, RunCurrent<CR><LF>
Query:	IR<CR><LF>

Arguments

RunCurrent

FLOAT

The motor run current in amps rms.

[Default:	1.044]
Minimum:	0
Maximum:	1.044

Returns

The motor run current in amps rms, rounded to the closest multiple of 1.044 A / 31 (approx. 33 mA).

Remarks

IR must be set equal to or smaller than IA. This is enforced by the SMD3; IA is automatically adjusted to be equal to IR, if a change to IR makes it greater than IA.

Examples

Tx: IR,1<CR><LF>

Rx: 0x0000,0x0000,1.0000E+00<CR><LF>

Tx: IR<CR><LF>

Rx: 0x0000,0x0000,1.0000E+00<CR><LF>

// Set run current to 1A

// Query run current

IA – Acceleration current

Set or query the motor acceleration/deceleration current.

Command:	IA, AccCurrent<CR><LF>
Query:	IA<CR><LF>

Arguments

AccCurrent

FLOAT

The motor acceleration current in amps rms.

[Default:	1.044]
Minimum:	0
Maximum:	1.044

Returns

The motor acceleration current in amps rms, rounded to the closest multiple of 1.044 A / 31 (approx. 33 mA).

Remarks

IA must be set equal to or greater than IR. The SMD3 will not force IA to match IR if IA is smaller than IR.

USB interface

Configuration

Protocol

Argument types

Flags

Error flags (EFLAGS)

Status flags (SFLAGS)

Error codes

Quick reference

General

Command movement

Motor

Limit inputs

Profile

Step/Direction

Bake

Command reference

General

IDENT - Blinks status indicator

MODE - Choose mode of operation

JSMODE – Joystick mode

AUTOJS – Auto switch to joystick mode

EXTEN – External enable used?

Command movement

RUNV – Run, velocity

RUNA – Run, absolute position

RUNR - Run, relative position

RUNB – Run bake

RUNH – Home to a limit switch

STOP – Stop motor

SSTOP – Stop motor in 1 s

ESTOP – Emergency stop

Motor

TSEL – Temperature sensor selection

TMOT – Motor temperature

IR – Run current

IA – Acceleration current

IH – Hold current

PDDEL – Power down delay

IHD – Current reduction delay

F – Freewheel mode

RES - Resolution

Limit inputs

L – Limits global enable

L+, L- Individual limit enable

LP+, LP- Individual limit polarity

LP – Global limit polarity

LSM – Limit stop mode

Profile

AMAX - Acceleration

DMAX - Deceleration

VSTART – Start frequency

VSTOP – Stop frequency

VMAX – Step frequency

VACT – Actual frequency

PACT – Actual position

PREL – Relative position

TZW – Zero wait time

THIGH – Microstep transition

EDGE – Edge to step on

INTERP – Step interpolation

Bake

BAKET – Bake temperature setpoint