Silicon Laboratories Stepper Machine User Manual download pdf (Page 2)

AN155

2 Rev. 1.1

turning. Press the function switch again. The motor will

rotate four turns the other direction.

It the LED does not illuminate, check the power

connection. If the motor does not turn, check the motor

wiring.

If using a stepper motor other than the GBM

42BYG205, follow the color code provided with that

particular stepper motor. Note that there is no standard

color code for stepper motor wiring. It is best to double-

check the wiring with a digital multi-meter. A 30 Ω

stepper motor should measure 60 Ω from A+ to A- and

30 Ω from A+ or A- to Acommon. Phase B should

measure similarly. A high impedance should be

obtained when measuring from any phase A wire to any

phase B wire.

2.2. Setting up HyperTerminal

Connect a DB9 serial modem cable to the stepper

motor reference design RS232 connector. Connect the

other end to a serial port on the back of a Windows PC.

Note which COM port is connected to the Stepper Motor

Reference Design.

Open HyperTerminal from the start menu.

Start>Programs>Accessories>Communication>HyperT

erminal. When prompted for a new connection name,

type in StepperMotor or some other descriptive name.

In the next dialog box, click on the connect using pull-

down menu and select the appropriate COM port (e.g.

COM4). Click on OK to exit the new connection dialog

box. In the next dialog box choose 57600 bits per

second, 8 data bits, no parity, 1 stop bit, and no flow

control.

Now hit return a few times. A prompt sign and a new

line should be displayed each time the return key is

depressed. If prompt is not displayed, double-check the

connections and the serial port settings. Make sure the

stepper motor board is plugged in and powered up. To

assist in debugging, test points are conveniently

provided for the TX and RX connections on the stepper

motor reference design.

2.3. Command Line Operation

The command line parser understands three

commands. The commands are p for position, a for

acceleration, and s for status. Each command must

start with a lowercase letter. The position and

acceleration commands are followed by a number

string.

Type s and the stepper motor will display the current

position and acceleration parameter. The text following

the prompt sign is always user input.

Position:

Acceleration:

The stepper motor will turn one complete rotation in 400

steps. Type p4000 and then hit enter. The stepper

motor will turn 10 rotations and then stop, While moving,

the terminal will display the message Moving... and

the current position of the motor. The display is updated

periodically while moving. When the move is complete

the number will stop at the final position and the

terminal will display the message done! and a

command prompt sign >.

>p4000

Moving...

Position:

4000

done!

Now type a120 and hit enter. The terminal will display

the new acceleration to verify the parameter change.

>a120

Acceleration:

120

Now type p0 and hit return. The stepper motor will

rotate ten turns the other direction at a slower rate.

A smaller number results in a faster acceleration and a

faster top speed. If you set the acceleration factor far

too small the motor will stall at the maximum slewing

speed. If the acceleration parameter marginally too

small, the motor will have very low torque in the slewing

region.

The parser will ignore any non-numeric characters

between the command letter and the first number. For

example p1000, p 1000, position 1000, and pig

1000 will all be interpreted as a position 1000

command. The parser does not understand capital

letters.

The number parsing is terminated by the first non-

numeric character. So it doesn’t really matter what you

type after the number. It could be a carriage return,

space, period, or any non-numeric character.

The number parser for the position expects an unsigned

16-bit integer. You can enter any position from 0 to

65535. If you enter 65536, it will be interpreted as a

zero. The acceleration parser expects an unsigned 8-bit

1 2 3 4 5 6 7 ... 35 36

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Silicon Laboratories Stepper Machine User Manual Page 2

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