Introducing the GCUSB-nStep2 stepper motor controller

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Email me if interested in more information: astrogene1000_stuff AT


Provides for:

USB interface or Standalone operation with/without wireless

Modular plugin expansion

Wireless interface for bluetooth communications

Display with buttons for configuration, speed and direction control, 16 char/2line

Adaptable for other uses (home sensor, rs232)

See ‘Technical Information’ below

Temperature sensor and temperature based focus (Standalone or provided by ASCOM driver)

Recall, Save and GoTo 5 positions as you change from eyepiece to camera, etc, just focus once and GoTo when you change

ASCOM driver supported over USB or wireless

Base module remembers all settings across power on’s

Firmware is field flash upgradeable on the main module

Temperature spec’s of –40C for main and wireless module, –20C for physical display or the display module

See GCUSB-nSTEP page for description of ASCOM driver

See Youtube demo videos part 1and Part 2


The unit with optional wireless, temperature probe and display module attached.

Temperature probe can have up to 5M long wiring,

Attach it right to the tube of your scope for accurate readings to +/- 0.5C

Coiled cords are 12ft long when fully expanded, take little space when contracted.

At this time the display unit circuit boards are on order and expected week of Jan 24.





Display module left, main module right

Main module left, display module right

Update March 3, 2011
These units are in continuous stock, available to ship in 2 days or 5 days
depending on whether I have units assembled, I usually always have units assembled and tested.
There is an up to 5 business day ship time for non-assembled units
These are custom built and tested for 4-8 hours each
If this is not acceptable to you, please do not buy

If more than available stock is ordered I will refund money immediately when oversold condition is recognized
( 24 hours max) and provide an expected availability date.

I will only ship to North and South America, Europe, Japan, Australia and New Zealand.
If you are from Italy -contact me- first for shipping quote
Orders from a country I will not ship to will be promptly refunded and not fulfilled

All units RoHS

30 day return (except for buyers remorse)
buyer pays return shipping
One year warranty

Main Module - $199.95 USD + shipping

Main module, USB cable, stepper cable, 12V DC adapter

Display module - $129.95.00 USD + shipping

Includes 12ft coiled cable to main module

Wireless Module - $94.95 USD + shipping

Includes 12ft coiled cable to main module

Temperature Sensor - $19.95 USD + shipping

Includes sensor and 6ft cable to main module

12V AC adapter - $19.95 USD + shipping

USA 2 prong plug, 100V-240V capable

View Cart

ASCOM driver screens

Temperature testing to -20C outside

It does not get super cold in the Philly area so I took advantage of one night with –20C temperatures

Unit is connected wireless, who wants to sit outside in the cold?
This image taken about 15 minutes after the next one, got too cold to stay outside!

Unit connected wireless to warm and cozy inside the house




The units up close in the cold showing -18.5C



The ouside environment




The base module


The Bluetooth module

Not much to see, led indicates paired and connected status.

Range 20 meters or 100 meters available




The Display unit



Buttons usage:

Upper left: Next menu

Upper right: Previous menu

Lower left: focus or change current menu item

Lower right: focus or change current menu item


Temperature compensated contrast, set it once and forget it!


The menu structure:


Top level menu showing:

Current position

Probe temperature

Step type (W/H/F)

Coils On/Off Current = 0 = off

Phase select: Current = 2

The current steps/second (149)


The stepper will move if the In/Out buttons pressed only in on top level menu.


The current position will update continuously if the main module or display module in/out buttons are pressed


The current steps/second will show the main modules rate if main module in/out buttons pressed.

The twist dial at top:

Set current step rate (now 88)

Will only range from 6 to Max Speed

(see below)


Select step type:

Top = W = Wave Stepping

Bottom = H = Half Stepping


Choices: Wave, Half or Full torque


Select Coils On/Off after movement

Top = 0 = Off

Bottom = 1 = Leave on

Set phase drive order:

Top = 2

Bottom = 1

Choices = 0, 1 or 2

This accounts for the wiring order of the stepper.

Set display brightness

Range = 0 (off) through 31

Set display contrast

Range = 14 through 31

Backlight on time

Range 10 through 310 seconds

After last button is pressed keep backlight on for this length of time


Set max step rate

Range 99 through 1496 steps/second


Force zero current position

Press up/down to zero, will confirm on next menu if up/down pressed.

To cancel, press menu select buttons


Confirm force zero position

Press p/down to zero.

To cancel, press menu select button


The bottom of the board


Technical Information:


1)      Stepping rates

The unit provides for a wide range of stepping rates, some of which can drive drastically faster than most steppers can handle.

The maximum rate is 1496 steps/second, the minimum rate is 5 steps/second. The maximum rate is controlled in the ASCOM driver and in the hand unit itself.

The display module provides for a more limited range of step rate selection, offering the choice of 25 speeds from 1496 to 6 steps/second.


2)      Stepper driver

The unit uses high voltage/medium current mosfet output drivers capable of driving 1 AMP/phase.


3) Optically coupled when PC attached

When connected to the PC/Mac, the output stages are isolated from the processing side via optical coupling.

The 12V supply is only used for the motor and the USB 5V is only used for the PIC, wireless and display module.

This prevents any voltage gound loop issues when connected to PC and stepper power supply.


3)      Standalone operation and Wireless

The base unit can be jumpered for running standalone without USB or wireless interface.

The base and optional modules then take power from the 12V supply.

Standalone operation uses same firmware load as wireless operation.


4)      Wireless

The expansion wireless module is based on the Roving Networks RN-41 (for 100m) or the RN-42 (for 10m-20m) for wireless interface.


At this time the USB and Wireless interfaces are mutually exclusive, both cannot communicate at the same time. It is two separate and distinct firmware modules that is loaded into the base unit.

Flashing firmware is an easy process on these units. A utility is provided that puts the unit into 'flash mode' and then launches the flash utility itself. You select the firmware load to be flash and press a button, about 10 seconds later it is complete.


5)      Expansion ports

The two expansion ports shown provide for 5V, GND, TX and RX TTL serial interfaces. This means that adapting the unit to rs232 DB9 serial interface in place of wireless is a simple add on module that converts rs232 voltages to TTL voltages. No firmware changes are required.


Pinouts (looking into the connector, upper left = pin 1)


Pin 1: 5V

Pin 2: Module RX (To module)

Pin 4: Module TX (From module)

Pin 4: GND


The Display port runs at 19.2k baud and the Wireless port runs at 9600 baud. Both are 8/N/1.


6)      Expansion port digital I/O

It is also possible to provide 2 digital I/O signals per expansion port in lui of serial communications. This means that adding a ‘home’ sensor is a simple add-on on module providing a logical ‘0’ or ‘1’ to indicate home position. Firmware supporting this is planned for the future.