Blog 15

Stepper Motor Raspberry Pi

In this part I am going to show my bash script for the raspberry pi version of rotating the stepper motor.

Hardware I used:

• RPi_UI board | (User Interface)
• 7fets | (7FETs)
• Jumper cables M-F
• IDC cable 6 pin
• 28BYJ-48 Stepper Motor

I connected the RPi_UI board with the 7fets through a spi cable(on spi0). The stepper motor I connected with the 7fets through 5 male-female cables. Cables blue till orange from the stepper motor I put on pin 2,4,6,8. ( 2 = blue 8 = orange ) The Red cable I putted on pin 3. It can also put on pin 1 or all the other dev power pins. (DIO protocol) You can see at the arduino set-up picture how I put them.

What my goal with the script was that the stepper motor should rotate with the value you gave it and stops for 10 seconds after that it has to start all over again.

The full script:

#!/bin/bash

Address="bw_tool -s 50000 -a 88"

Rot=-400
Target=`$Address -R 41:i`
#Speed=200
#$Address -W 43:$Speed:b`

Current="" 

while true; do 
  $Address -W 42:$Rot:i
  Target=`$Address -R 41:i`
  while [ "$Current" != "$Target" ] ; do
    sleep 0.2
    Current=`$Address -R 40:i`
  done
  sleep 10
done

Address="bw_tool -s 50000 -a 88"

Here I put the address of the script, where the script can reference multiple times to.

Rot=-400 

With changing the number after rot you can change the amount of rotation. That the script has to do later. With 400 it turns 180 degrees. And with minus it turns right without minus it turns right-ways.

Target=`$Address -R 41:i`

With target it will give the position it currently is in. This is for making it equal to the current.

#Speed=200
#$Address -W 43:$Speed:b`

This is something I added to the code. With this you can change the step delay. For now I gave it 200, what is equal to 20ms. So if you want it to turn faster you have to make the step delay less.

Current="" 

This is to give current for now no worth. So that in the script it will directly start running the stepper motor.

$Address -W 42:$Rot:i
Target=`$Address -R 41:i`

Here I reference the rot and address commands and want it to rotate the amount of give in the rot part. And here again it asks for the target location with the second line.

while [ "$Current" != "$Target" ] ; do
  sleep 0.2
  Current=`$Address -R 40:i`

Here it looks if the current place of the rotating stepper motor is not equal to the target. If so it will re-look after 0.2 seconds what the current is. And when it is equal it will sleep for 10 seconds and then start all over again:

  done
  sleep 10
done

Working with stepper motor

In this post I am going to connect a stepper motor with my Arduino. I want the stepper motor to turn left and right, and I want the stepper motor to turn a certain degrees.

Before programming I first need to connect the Arduino with the stepper motor.

The hardware I used:

• 7fets | (7FETs)
• 28BYJ-48 Stepper Motor
• Jumper cables M-F
• IDC cable 6 pin

( I also posted in Blog 14, I connected the 7fets with an lcd + display. This is something what of course is not needed )

As you can see in the image is that the stepper Motor has 5 coloured cables, that are all together in a white cube. These cables have to get connected with the 7fets. To do this you have to get 5 male to female cables. From cable blue to orange from the stepper motor it has to be connected to pin 2,4,6,8. The red cable can be put on pin 1, all the other places in the row that are dev power. ( Places where it can gets it's voltage ) ( out 1 till 4 , works different counts 0 till 3) ( in 1 till 4 ) 7FETs

Now the programming part:

I used a script named ardemo_lcd.pde, that I changed to get it working with the stepper motor.

const int SPICLK  = 13;
const int SPIMOSI = 11;
const int SPIMISO = 12;
const int SPISS  = 10;

void SPIinit(void)
{
  pinMode (SPICLK,  OUTPUT);
  pinMode (SPIMOSI, OUTPUT);
  pinMode (SPIMISO, OUTPUT);
  pinMode (SPISS,   OUTPUT);
  digitalWrite (SPISS, 1);
   
  SPCR    =  _BV(SPE) | _BV(MSTR) | _BV(SPR1) | _BV(SPR0);
} 

char SPI(char d) 
{  // send character over SPI
  char received = 0;
  SPDR = d;
  while(!(SPSR & _BV(SPIF)));
  received = SPDR;
  return (received);
} 

void SPI_startpkt (void)
{
 digitalWrite (SPISS, 0);
}

void SPI_endpkt (void) 
{
  digitalWrite (SPISS, 1);
}

void set_var32 (unsigned char addr, unsigned char a, unsigned long v)
{
  SPI_startpkt ();
  delayMicroseconds (WAIT1);
  SPI (addr);
  delayMicroseconds (WAIT2);
  SPI (a);
  delayMicroseconds (WAIT2);
  SPI (v);
  delayMicroseconds (WAIT2);
  SPI (v>>8);
  delayMicroseconds (WAIT2);
  SPI (v>>16);
  delayMicroseconds (WAIT2);
  SPI (v>>32);
  delayMicroseconds (WAIT2);
  SPI_endpkt ();   
}

static unsigned char spi_7fet_addr = 0x88;

void setup() {
  //declare the motor pins as outputs
  SPIinit ();  
  Serial.begin(9600);
}

void loop(){
  set_var32 (0x88, 0x42, 0x50);
  delay(1000); 
}

void setup() {
  //declare the motor pins as outputs
  SPIinit ();  
  Serial.begin(9600);
}

void loop(){
  set_var32 (0x88, 0x42, 0x50);
  delay(1000); 
}

This says that at address 0x88 from the 7fets it has to go 50 further from the current position and after that it should take a 1 sec break. ( repeat and repeat itself) If you want to let the stepper motor to turn the other way you have to add a minues before 0x50. Example:

   set_var32 (0x88, 0x42, -0x50);

0x42 is for setting the relative position. ( so in the example script it goes 50 further from the current position ) Port 42 is 32bits, don't forget about if a port is 32bits or not. ( On the DIO protocol you can find all the ports. )

Rotating Plateau

Now I want to explain how you could rotate the stepper motor a certain degrees and in which direction. This can be handy if you want to use the stepper motor as plateau for a museum, or of course other projects were you need a stepper motor.

For this I will only paste the setup + loop. ( The other parts you can just copy paste from the previous code. I didn't want to make this page too long )

//beta

 void loop(){
 set_var32 (0x88, 0x42, 0x200);
 delay(1000);  
 }

This script makes it possible that it turns 90 degrees with the register 0x200.

The values with the amount of rotation they make: 0x800 = 360 degrees 0x400 = 180 degrees 0x200 = 90 degrees 0x267 = 120 degrees

If you want another degree like for instance 45 you can just convert it. Example 800:360 = 2.2222222 * 45 = 100

The final script to make it all work:

---

unsigned long get_var32 (unsigned char addr, unsigned char a)
{
  unsigned long v;
  
  SPI_startpkt ();
  delayMicroseconds (WAIT1);
  SPI (addr+1);
  delayMicroseconds (WAIT2);
  SPI (a);
  delayMicroseconds (WAIT2);
  v = (unsigned long)SPI (0x00);
  delayMicroseconds (WAIT2);
  v |= (unsigned long)SPI (0x00) << 8;
  delayMicroseconds (WAIT2);
  v |= (unsigned long)SPI (0x00) << 16;
  delayMicroseconds (WAIT2);
  v |= (unsigned long) SPI (0x00) << 24;
  delayMicroseconds (WAIT2);
  SPI_endpkt ();    
  return v;
}   

/*
unsigned char get_var (unsigned char addr, unsigned char a)
{
  unsigned char v;
  
  SPI_startpkt ();
  delayMicroseconds (WAIT1);
  SPI (addr+1);
  delayMicroseconds (WAIT2);
  SPI (a);
  delayMicroseconds (WAIT2);
  v = SPI (0x00);
  delayMicroseconds (WAIT2);
  SPI_endpkt ();    
  return v;
}
*/   

//Time to pause rotating
static unsigned long Pause = 10000;
//Amount you want the stepper motor to rotate (0x200 = 25%  0x400 = 50% 0x800= 100% )
static unsigned long Rot = 0x200;  

void setup() { 
  //declare the motor pins as outputs
  SPIinit ();  
  Serial.begin(9600);
  char buf[32];
  unsigned long Tar;
  unsigned long Cur;  

  //Makes the current(0x40) + current(0x41) zero. Handy if the current + target have a too big difference. 
  //set_var32(0x88, 0x40, 0x00);
  // set_var32(0x88, 0x41, 0x00); 

  //Change the step delay //50 is 4 times as fast as he normally goes (200)
  //set_var(0x88, 0x43, 50);
 
  Tar = get_var32 (0x88, 0x41);
  sprintf (buf, "FTarget: %08lx\r\n", Tar );
  Serial.write (buf); 

  Cur = get_var32 (0x88, 0x40);
  sprintf (buf, "Fcur:    %08lx\r\n", Cur);
  Serial.write (buf);
} 

void loop()
{
  unsigned long v;
  unsigned long Cur;
 
  static long Rot = 0x200;
  char buf[32];
  set_var32(0x88, 0x42, Rot);  

  v = get_var32 (0x88, 0x41);
  sprintf (buf, "Target:  %08lx\r\n", v);
  Serial.write (buf); 

  do {
    delay(200);
    Cur = get_var32 (0x88, 0x40);
    sprintf (buf, "cur:     %08lx\r\n", Cur);
    Serial.write (buf);   

  } while (Cur != v); 

  delay(Pause);  
}