AN1794 datasheet(7/34 Pages) STMICROELECTRONICS

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AN1794

Starting practiSPIN

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Starting practiSPIN

Since the practiSPIN system is capable of supporting several driver IC's and driving different

types of motors the user must first select the type of motor to be driven and the driver IC that

will be evaluated.

Target board set up: configure the jumpers/switches on the target board and the ST7

interface board as described in the paragraph for the specific evaluation board being

used.

Control board - PC connection: connect the ST7 interface board to a serial COMM port

of the PC via a standard (straight through) 9 pin D connector cable.

Power up: energize the power supply.

Start practiSPIN software: on the PC, start the practiSPIN program.

Motor type selection: on the first screen of the practiSPIN software, the user can select

the appropriate type of motor for the device under evaluation. Click on the appropriate

motor type.

Communication settings: click the drop down list under "port selection" and select the

COMM port being used. Baud rate and other communication parameters are fixed on

both sides of the link and do not need to be set.

Establish COMM link: click the "Connect With ST7 Hardware". At this point the

practiSPIN software will transmit several commands to the ST7 to initialize the

processor. The practiSPIN software will read the revision code of the firmware currently

stored in the flash memory of the ST7 and determine if the correct version of firmware

resides in the ST7. If the practiSPIN software detects that a firmware update is

necessary, either because there is an old version of firmware or the firmware currently

in the flash memory is not the correct firmware for the motor type selected, one or more

dialogue boxes will appear asking if the program should proceed with the update.

Accept the updates and the practiSPIN software will automatically update the firmware.

The system will then initialize the settings to the last stored settings and open the

appropriate practiSPIN software for the selected motor type.

Calibrate current setting: when communication is established the user has the option to

adjust the offset and maximum current settings. If this is the first time you use the

system, calibration may be needed to adjust out the offset in the reference bias

circuitry. Calibration ensures that the reference voltage provided to L62XX IC follows

the practiSPIN software current settings. Calibration is a two-step process; first the

offset is adjusted then the maximum current is set.

To null out the offset, click on CALIBRATE ZERO then adjust R18 (on ST7 board)

until voltage at Vref pin(s) of the L62XX device is zero. Measurement points on

each board are listed in the set up section for each target board.

The maximum current, corresponding to 100% current setting in the practiSPIN

software, can be adjusted using the Vref potentiometers on the target board. If the

potentiometers are set to full scale (clockwise) the reference applied to the input of

the device is typically about 0.88 V. The full-scale peak current is equal to

Vref/Rsense where Rsense is the composite value of the sense resistor on the

board. To set the maximum current, click on CALIBRATE MAX and trim the Vref

potentiometer(s) on the EVAL62XX board to set the desired reference. If you plan

to use microstepping, consider reducing the maximum Vref to the real peak value

you will use, allowing setting the software current controls near to 100%, avoiding

poor Vref resolution.

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