Take a look at this code that @wawa wrote for a 24 shift register board. Adjust it for a single shift register.
#include <SPI.h>
#define motors 24 // in lots of four motors - On my board
const byte clrPin = 7; // TPIC6B595 SRCLR pin - Dummy Pin - ON MY BOARD, SRCLR IS HIGH
const byte activityPin = 8; // On my board
const byte oePin = 9; // On my board
const byte latchPin = 10; // TPIC6B595 RCK pin
const byte rampSteps = 4; // accel/decel steps
byte rampDelay[motors]; // accel/decel delay between steps
byte lag[motors]; // speed reduction
int velocity[motors]; // signed, for direction
int nowPos[motors], newPos[motors]; // int>long=+220us
unsigned long prevMicros; // timing
byte val[4]; // TPIC write bytes
unsigned long start; // 4 testing
bool T0, T1, T2, T3; // 4 testing
unsigned long prevMillis; // 4 testing
byte x;
void setup() {
Serial.begin(115200); // 4testing
SPI.begin();
//pinMode(clrPin, OUTPUT);
//digitalWrite(clrPin, HIGH); // clean start
pinMode (oePin, OUTPUT);
digitalWrite (oePin, LOW);
pinMode(latchPin, OUTPUT);
digitalWrite (latchPin, LOW);
for (x = 0; x < 12; x = x + 1) {
SPI.transfer(0); // clear all shift registers
}
digitalWrite (latchPin, HIGH);
pinMode (activityPin, OUTPUT);
for (x = 0; x < 3; x = x + 1) {
digitalWrite (activityPin, HIGH); // flash the onboard LED
delay (250);
digitalWrite (activityPin, LOW);
delay (250);
}
}
void loop() {
// sumdumtest
if (!T0 && millis() - prevMillis > 1000) {
for (byte i = 0; i < motors; i++) { // all motors
lag[i] = 0;
newPos[i] = 512; // 1/4 turn
}
T0 = true;
}
if (!T1 && millis() - prevMillis > 3000) {
for (byte i = 0; i < motors; i++) { // all motors
lag[i] = 0;
newPos[i] = -511; // 1/2 turn
}
T1 = true;
}
if (!T2 && millis() - prevMillis > 6000) {
for (byte i = 0; i < motors; i++) { // all motors
lag[i] = 0;
newPos[i] = 0; // back to zero
}
T2 = true;
}
if (millis() - prevMillis > 8000) {
prevMillis = millis();
T0 = false;
T1 = false;
T2 = false;
}
goPos(); // let's step
}
void goPos() {
while (micros() - prevMicros < 2440); // minimum step interval, 12RPM motor limit
prevMicros = micros(); // update, for next interval
//start = micros(); // 4testing
for (int i = 0; i < motors; i++) {
if (rampDelay[i]) rampDelay[i]--; // subtract one, do nothing
else { // step
if (newPos[i] > nowPos[i]) { // request forwards
if (velocity[i] >= 0) { // if standing still, or going forwards
nowPos[i]++; // one step forward
if (newPos[i] - nowPos[i] < rampSteps) velocity[i]--; // reduce speed if almost there
else if (velocity[i] < min(rampSteps, rampSteps - lag[i])) velocity[i]++; // increase speed if not there yet
rampDelay[i] = max(lag[i], rampSteps - velocity[i]); // insert ramp delay
} else { // if wrong direction
velocity[i]++; // reduce reverse speed
if (velocity[i] < 0) nowPos[i]--; // if still reverse, keep on going the wrong way
rampDelay[i] = rampSteps - abs(velocity[i]); // insert ramp delay
}
}
if (newPos[i] < nowPos[i]) { // request reverse
if (velocity[i] <= 0) { // if standing still, or going reverse
nowPos[i]--; // one step reverse
if (nowPos[i] - newPos[i] < rampSteps) velocity[i]++; // reduce speed if almost there
else if (abs(velocity[i]) < min(rampSteps, rampSteps - lag[i])) velocity[i]--; // increase speed if not there yet
rampDelay[i] = max(lag[i], rampSteps + velocity[i]); // insert ramp delay
} else { // wrong direction
velocity[i]--; // reduce forward speed
if (velocity[i] > 0) nowPos[i]++; // if still reverse, keep on going the wrong way
rampDelay[i] = rampSteps - velocity[i]; // insert ramp delay
}
}
}
if (newPos[i] == nowPos[i])val[i & 3] = 0; // cut coil power when there
else {
switch (nowPos[i] & 3) { // the two LSB translated to motor coils (full step)
// this block for torque
//case 0: val[i & 3] = B00000011; break;
//case 1: val[i & 3] = B00001001; break;
//case 2: val[i & 3] = B00001100; break;
//case 3: val[i & 3] = B00000110; break;
// or this block for low power
case 0: val[i & 3] = B00000001; break;
case 1: val[i & 3] = B00001000; break;
case 2: val[i & 3] = B00000100; break;
case 3: val[i & 3] = B00000010; break;
} // order is important for not missing steps when coil power is cut
}
if ((i & 3) == 3) { // process set of four motors (faster)
unsigned int chain = val[0] << 12 | val[1] << 8 | val[2] << 4 | val[3]; // concat
SPI.transfer16(chain); // transfer 4-motor int
}
}
digitalWrite(latchPin, HIGH); // transfer to TPIC driver outputs
digitalWrite(latchPin, LOW); // latch time ~8us
//Serial.println(micros() - start); // 4testing, must stay well below step interval
}
TPIC6B595 can drive a motor directly in place of a 74HC595 and ULN2003.
Its TPIC6B595 and 74HC595 are both controlled identically.
