MST 400-200 WK — RS-232 Communication Reference

Complete reference for serial communication, configuration, and parameter programming of the Plettenberg MST 400-200 WK motor controller.

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Table of Contents

• Physical Connection
• Interface Parameters
• Pin Allocation
• Minimal Wiring
• Startup Behaviour
• Operational Commands
• Adjust Mode
• Configuration Parameters
• Live Data Output Protocol
• RS232 Control Examples

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Physical Connection

Required Hardware

You will need one of the following to connect a PC:

• USB → RS-232 serial adapter
• MST programming adapter (optional order)
• Standard serial cable (not a null-modem cable)

IMPORTANT

Do not use a null-modem (crossover) cable. Use a straight-through serial cable.

For cable lengths over 2 m, screened CAT5 cable must be used. Cable length and quality directly affect signal integrity.

Recommended Cable Types (available from Plettenberg, per metre)

Part Number	Type	Conductors
Alpha Wire 3306 SL005	Sensor cable	6 × AWG28
Alpha Wire 3308 SL005	Sensor cable	8 × AWG28
Alpha Wire 3310 SL005	Sensor cable	10 × AWG28

All cables comply with MIL-W 16878 Type B specification.

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Interface Parameters

The RS-232 interface is fixed at the following settings:

Parameter	Value
Baud rate	115,200 baud
Data bits	8
Parity	None
Stop bits	1

NOTE

This is commonly written as 115200/8N1. Make sure your serial terminal is configured exactly to these values or the controller will not respond correctly.

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Pin Allocation

The MST uses a DE-9 (Sub-D 9-pin male) connector for RS-232, analog, and digital signals.

Standard Analog / Digital / RS-232 Variant

DE-9 (front view, male connector)

 ┌─────────────────────┐
 │  1   2   3   4   5  │
 │  ●   ●   ●   ●   ●  │
 │    6   7   8   9    │
 │    ●   ●   ●   ●    │
 └──○─────────────────○┘

Pin	Designation	Description
1	Brake input (Aux)	Analog input 0–5 V
2	RxD	RS-232 receive signal
3	TxD	RS-232 transmit signal
4	Reverse switch	0 V = Forward / 5 V = Reverse
5	GND	Signal Ground
6	Throttle input	Analog input 0–5 V
7	DNC	Do not connect
8	Impulse input	5 V Digital input
9	+5 V (max. 30 mA)	Potentiometer supply

Optional CAN 2.0 / RS-232 Variant

Pin	Designation	Description
1	RxD	RS-232 receive signal
2	CAN-H	CAN high signal
3	CAN-L	CAN low signal
4	NC	Not connected
5	NC	Not connected
6	TxD	RS-232 transmit signal
7	GND	Signal Ground
8	DNC	Do not connect
9	+5 V (max. 30 mA)	Supply for additional equipment

WARNING

The cable shield should be connected to Pin 9 (GND) only. Do not connect the shield to the battery negative terminal or the motor controller housing.

CAUTION

The interfaces are not galvanically isolated. A short-circuit on the 5 V supply can destroy the Hall sensor power supply and potentially damage the controller while the motor is running.

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Minimal Wiring

For RS-232-only configuration (no analog control), connect only the essential signals between the MST and the PC/RS-232 adapter:

MST (DE-9)          PC / RS-232
──────────          ───────────
  Pin 2 (RxD)  ←── Pin 3 (TxD)
  Pin 3 (TxD)  ──→ Pin 2 (RxD)
  Pin 5 (GND)  ─── Pin 5 (GND)

TIP

When adding analog throttle, analog braking, and a reverse switch, also connect:

• Pin 6 (Throttle input) via a 5 kΩ potentiometer between Pin 9 (+5 V) and Pin 5 (GND)
• Pin 1 (Brake/Aux input) via a 5 kΩ potentiometer similarly
• Pin 4 (Reverse switch) to a toggle switch between Pin 5 (GND) and Pin 9 (+5 V)

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Startup Behaviour

When power is applied, the MST immediately outputs a startup message over RS-232 containing the current configuration and command list:

* Kommandoliste:
* 's' Serieller Sollwert
* 'p' Poti Sollwert
* 'i' Impuls Sollwert
* 'f' Forward
* 'r' Reverse
* '0' Off
* 'b' Brake
* 'm' 100% PWM(max)
* '9' 90% PWM
...
* 'w' write setup
* 'h' Help

MST400-200 V8.4
Input = Analog
AnalogStop/Start/Full/BrakeMax = 500mV/549mV/4499mV/4499mV
ImpulsStop/Start/Full = 1150µs/1200µs/1900µs
Timing Forward/Reverse = 0° / 40°
...

NOTE

On power-up, the controller always defaults to Analog input mode, regardless of previous serial sessions. You must send s to switch to serial control each time.

IMPORTANT

If the MST was delivered with CAN 2.0 firmware, the CAN bus interface is active immediately after power-up. While CAN messages are being received, switching to serial control input is blocked.

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Operational Commands

All commands are single-byte (1 character). No CR/LF is required at the end of any command.

Input Source Selection

Command	Description
s	Switch to serial RS-232 input
p	Switch to analog input (potentiometer)
i	Switch to pulse (PWM) input

Direction Control

Command	Description
f	Forward
r	Reverse

WARNING

Reversing direction on motors with advanced timing significantly reduces power and efficiency. For high-power reverse applications, use a motor with neutral timing.

Throttle Control

Command	PWM Level
m	100% (maximum)
9	90%
8	80%
7	70%
6	60%
5	50%
4	40%
3	30%
2	20%
1	10%
+	+1% (increment)
-	−1% (decrement)
g	+0.1% (firmware V2+)
l	−0.1% (firmware V2+)

Stop & Brake

Command	Description
0	Stop (cut motor current)
b	Brake

Utility

Command	Description
h	Help — re-outputs the command list
t	Activate timeout for serial interface (firmware V2+)
a	Enter Adjust mode (configuration)
e	Exit Adjust mode (without saving)

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Adjust Mode

Adjust mode allows reading and writing persistent configuration parameters.

Entering Adjust Mode

1. Power on the MST
2. Send:  s    ← switch to serial input
3. Send:  a    ← enter Adjust mode

NOTE

Both s and a must be sent after the initialisation phase completes (i.e. after the startup message has been printed).

2-Byte Commands (Adjust Mode)

Command	Description
sd	Set all parameters to default values
sp	Show (print) current parameters
wp	Write (save) parameters to non-volatile memory
se	Show the last 8 errors

TIP

Always end a configuration session with wp to persist your changes. Sending e exits without saving.

Exiting Adjust Mode

Command	Effect
wp	Save and remain in Adjust mode
e	Exit without saving

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Configuration Parameters

All configuration uses 5-byte commands: a 2-letter code followed by a zero-padded 3-digit value (e.g. cl200 sets current limit to 200 A).

Speed & Current Limits

Command	Description	Range	Default	Unit
rp	RPM limit	001–240	240	× 1000 rpm
cl	Phase current limit	010–300	300	A
il	Input (battery) current limit	010–300	300	A

IMPORTANT

Set pole pairs (pp) before setting the RPM limit (rp). The pole pair count directly affects the real shaft speed limit.

To set a finer speed limit (e.g. ~2500 RPM on a 30-pole motor):

1. pp001 — temporarily set pole pairs to 1
2. Calculate: 15 pp × 2500 RPM = 37,500 eRPM
3. rp038 — set limit (38 × 1000 = 38,000 eRPM)
4. pp015 — set correct pole pairs (15 pairs = 30 poles)
5. Verify with sp → should show ~2533 RPM
6. wp — save

Voltage Limits

Command	Description	Range	Default	Unit
uv	Undervoltage cutoff	010–050	010	V
ov	Overvoltage cutoff	014–063	060	V

CAUTION

Hardware overvoltage protection triggers at 400 V (shutdown) and 405 V (risk of damage), regardless of the ov software setting.

Temperature Limits

Command	Description	Range	Default	Unit
mt	Motor temperature limit	070–100	100	°C
ct	Controller temperature limit	070–110	110	°C

WARNING

The controller will hard-shut down at 110 °C internally, regardless of the ct setting. Always ensure adequate water cooling (recommended: 4–7 L/min at ≤ 1.5 bar, 25 °C inlet temperature).

Throttle — Forward Direction

Command	Description	Range	Default	Unit
te	Throttle exponential curve	000–100	000	%
ti	Throttle increase rate	001–653	131	count/ms
td	Throttle decrease rate	001–999	328	count/ms
tl	Throttle limit (max position)	005–100	100	%
tm	Throttle minimum (start point)	001–100	002	%

Throttle — Reverse Direction

Command	Description	Range	Default	Unit
ri	Reverse throttle increase rate	001–653	066	count/ms
rd	Reverse throttle decrease rate	001–999	328	count/ms
rl	Reverse throttle limit	005–100	100	%
rm	Reverse throttle minimum	001–100	002	%

Brake Parameters

Command	Description	Range	Default	Unit
bi	Brake increase rate	001–653	131	count/ms
bd	Brake decrease rate	001–653	328	count/ms
bl	Brake limit	001–100	100	%
bm	Brake minimum	000–100	005	%

TIP

At bl100 (100% brake), the motor is fully short-circuited and no braking energy is returned to the battery. If a mechanical brake is also present, set bl to a maximum of 90%.

Analog Input Calibration

Command	Description	Range	Default	Unit
ab	Full braking analog input voltage	006–498	450	× 1/100 V
af	Full throttle analog input voltage	122–498	450	× 1/100 V
ah	Stop (halt) analog input voltage	012–366	050	× 1/100 V
as	Start analog input voltage	018–379	055	× 1/100 V

NOTE

Values are in units of 1/100 V, so 450 = 4.50 V, 050 = 0.50 V.

TIP

Dual-input vs. single-input mode is controlled by the ab value:

• If ab > ah: controller uses Throttle for acceleration + Aux for braking (two separate inputs)
• If ab < ah: controller uses the Throttle input only for both — suited for a centre-neutral lever

CAUTION

If ah is set too low, a Hall-sensor throttle grip (min output ~1.2 V) may prevent the controller from detecting "stop" on power-up, leaving the motor locked out. Set as at least 0.02–0.1 V above ah to avoid rapid on/off switching at low throttle.

WARNING

If af is set too high (above ~4.1 V), Hall-sensor throttle grips may never reach full throttle due to their limited output voltage range.

Pulse (PWM/RC) Input Calibration

Command	Description	Range	Default	Unit
if	Full throttle pulse width	120–220	190	× 10 µs
ih	Stop (halt) pulse width	080–170	115	× 10 µs
is	Start pulse width	085–175	120	× 10 µs

NOTE

Values are in units of 10 µs, so 190 = 1.90 ms, 115 = 1.15 ms. Most RC receivers default to 1.1 ms (stop) and 1.9 ms (full throttle). Set is around 5 counts (50 µs) above ih to avoid hunting at low throttle.

Motor & Interface Settings

Command	Description	Range	Default	Unit
pp	Number of motor pole pairs	001–100	001	—
ot	RS-232 output repeat interval	007–999	200	ms
id	CAN bus base ID	000–999	256	—

Output Repeat Time Reference (ot)

Value	Update Rate
200	5 Hz
100	10 Hz
050	20 Hz
025	40 Hz
020	50 Hz
010	100 Hz
008	125 Hz

Acceleration/Deceleration Rate Reference

Applies to ti, td, ri, rd, bi, bd:

Value	Ramp Time
653	0.1 s
326	0.2 s
218	0.3 s
163	0.4 s
131	0.5 s
093	0.7 s
065	1.0 s
044	1.5 s
033	2.0 s
001	65.3 s

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Live Data Output Protocol

While the motor is running, the MST continuously sends telemetry over RS-232 at the interval defined by ot.

Analog Control Mode Output

T=3.649V,a=0.000V,PWM= 787,U= 34.9V,I= 3.7A,RPM= 1482,con= 28°C,mot= 26°C

Serial Control Mode Output

S=3.649V,a=0.000V,PWM=1000,U= 35.0V,I= 4.0A,RPM= 1896,con= 28°C,mot= 26°C

NOTE

The first field changes designator depending on active input mode:

• T = Throttle (analog input active)
• S = Serial input active

Brake Active Output

When braking is active, the throttle and aux designators swap case:

t=0.000V,A=2.501V,PWM= 500,U= 35.0V,I= 0.0A,RPM= 0,con= 28°C,mot= 26°C

• t (lowercase) = throttle is inactive
• A (uppercase) = Aux/Brake input is active

Field Reference

Field	Description	Unit
T / t	Throttle input voltage	V
a / A	Aux/Brake input voltage	V
PWM	Pulse width modulation value	‰ (0–1000)
U	Input (battery) voltage	V
I	Phase current	A
RPM	Rotational speed	rpm
con	Motor controller temperature	°C
mot	Motor temperature	°C

NOTE

PWM is reported in per-mille (‰), not percent. A value of 1000 = 100%.

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RS-232 Control Examples

Basic Drive Sequence

s          ← switch to serial control (required after power-up)
f          ← set direction: forward
1          ← 10% throttle PWM
+++        ← 13% throttle (three +1% steps)
3          ← jump to 30% throttle
m          ← full throttle (100%)
0          ← stop motor

Combined Command Sequences

1f         ← run forward at 10% throttle
3+++       ← increase throttle to 33%
m          ← increase to maximum throttle
0          ← switch off motor current
1b         ← brake at 10% brake PWM
3+++       ← increase brake to 33%
1--r       ← run at 8% throttle in reverse

Configuration Session Example

s          ← switch to serial mode
a          ← enter Adjust mode

sp         ← show all current parameters

cl180      ← set phase current limit to 180 A
il150      ← set input current limit to 150 A
uv028      ← set undervoltage cutoff to 28 V
mt090      ← set motor temperature limit to 90 °C
pp025      ← set motor pole pairs to 25
rp240      ← set RPM limit to 240,000 eRPM
ti131      ← throttle ramp up: 0.5 s
td328      ← throttle ramp down: 0.2 s
ot010      ← set output to 100 Hz

wp         ← write (save) all parameters

e          ← exit Adjust mode

TIP

Use se in Adjust mode to retrieve the last 8 error codes — useful for diagnosing intermittent faults that have already cleared.

IMPORTANT

Use sd with caution — it resets all parameters to factory defaults and requires a full reconfiguration of your setup.

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Error Codes & Status LED

The status LED on the connection side reflects the controller's fault state.

LED Behaviour	Fault	Error Code
Steady ON	No fault	—
1 flash	Undervoltage	0x0001
2 flashes	Overvoltage	0x0002
3 flashes	Overcurrent	0x0004
4 flashes	Controller overtemperature	0x0008
5 flashes	Motor overtemperature	0x0010
6 flashes	Motor jammed	0x0020
7 flashes	Sensor fault	0x0040
9 flashes	Analog input fault (wire break)	0x0100
10 flashes	Pulse width fault	0x0200

NOTE

Multiple faults can be active simultaneously. Error codes are bitwise OR'd together. For example: 0x0240 = Pulse width fault (0x0200) + Sensor fault (0x0040).

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Document based on Plettenberg MST 400-200 WK Operating Manual — OM_MST_400-200_WK_V8.10_ENFirmware Version 8 · © 2022 Plettenberg Elektromotoren GmbH & Co. KG