AN1794

System overview

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1

System overview

To illustrate the operation of the practiSPIN system, we will look at one typical device

supported by the system.

The L6207 includes two independent full or H bridges with separate logic inputs and current

control functions.

The two bridges are designated A and B and their output pins designated as OUT1A,

OUT2A, OUT1B, and OUT2B. These outputs are controlled independently by logic inputs

IN1A, IN2A, IN1B, and IN2B respectively.

A logic high or low on any of these inputs will drive its corresponding output to the positive

supply rail or to ground. Both of the A outputs will be forced to an off (high impedance) state

if the ENA pin is taken logic low, as will the B outputs if ENB is taken low. The L6207 is thus

controlled by six logic inputs: IN1A, IN2A, and ENA controlling bridge A and IN1B, IN2B, and

ENB controlling bridge B. Each bridge also has an analog control signal, VREFA and

VREFB, which control the current.

1.1

Target board

The L6207 target board gives access to the bridge A and B outputs at connectors CN3 and

CN4 respectively.

When driving a stepper motor, the two wires from one of the motor windings will connect to

CN3 and the other winding will connect to CN4. Swapping between the two connectors or

swapping the polarity at a given connector will only reverse the sense of motor direction. DC

supply power in the range of 12 to 48 Vdc is connected at CN1. The polarity marked on the

board silkscreen must be strictly observed! The eight control signals are taken from the 34-

pin ribbon header (CN5) and are driven by the control interface PCB via a short flat cable.

1.2

Control interface board

The control interface PCB is based on an ST72F264 microcontroller. The micro includes a

UART and communicates with the practiSPIN software via 9 pin D connector P1 employing

a standard RS232 interface.

The micro is based on flash memory and its firmware includes a write protected boot-loader

routine that allows the practiSPIN software to update or change the operating program in the

ST7 as required for different target boards. 5 Vdc power for the board is received via the 34-

pin ribbon cable from the target board or can be directly supplied at J2 if jumper WJ1 is

removed. The eight control signals for the target board are generated by the ST7 micro. The

six logic signals are generated directly by six of the eight pins of port B while the two analog

current references (VREFA and VREFB) are generated by pulse width modulated (PWM)

signals generated by the ST7 along with an offset adjusting circuit controlled by

potentiometer R18.