Using SPI modules with an arduino - Revision history

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2018-01-16T13:55:41Z

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Rew: /* software */

2016-09-29T07:55:54Z

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2016-09-29T07:55:37Z

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Rew: /* software */

2016-09-29T07:53:11Z

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Rew: Created page with "= intro = It is very convenient to expand your arduino with the bitwizard I2C or SPI modules. This article focuses on the SPI variant. == hardware == To connect your bitwi..."

2016-09-29T07:51:47Z

Created page with "= intro = It is very convenient to expand your arduino with the bitwizard I2C or SPI modules. This article focuses on the SPI variant. == hardware == To connect your bitwi..."

New page

= intro =

It is very convenient to expand your arduino with the bitwizard I2C or SPI modules. This article focuses on the SPI variant.

== hardware ==

To connect your bitwizard module to your arduino I prefer to use the connector on the arduino that is originally for ICSP. Almost all the SPI signals are there. And we chose the pinout to be the same as well.

The only signal that does not appear on the ICSP connector is the "slave select" signal. The ICSP connector has "RESET" there.

So use the following connection:

arduino bitwizard
ICSP SPI
1 1
2 2
3 3
4 4
6 6

[todo find the names of the signals]

This leaves SS/RESET. We cannot use the RESET line on the ICSP connector. We recommend you use the D10 pin of the arduino as that is the pin recommended for the purpose by the chip manufacturer Atmel. So:
arduino bitwizard
SPI
D10 5

== software ==

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);
}

static unsigned char bigrelay = 0x9c;

#define WAIT1 25
#define WAIT2 15

setregval (unsigned char addr, unsigned char reg, unsigned char val)
{

SPI_startpkt ();
delayMicroseconds (WAIT1);
SPI (addr);
delayMicroseconds (WAIT2);
SPI (reg);
delayMicroseconds (WAIT2);
SPI (val);
SPI_endpkt ();
}

void setup (void)
{
int i;

SPIinit ();
pinMode (myswitch, INPUT_PULLUP);
}

void loop (void)
{
static int r;

if (digitalRead (myswitch) == 0) {
r = r + 1;
if (r == 6) r = 0;
setregval (bigrelay, 0x10, 1 << r);
delay (10); // debounce
while (digitalRead (myswitch) == 0)
/* nothing */ ;
delay (10); // debounce.
}
}

@@ Line 74: / Line 74: @@
  #define WAIT2 15
- setregval (unsigned char addr, unsigned char reg, unsigned char val)
+ void setregval (unsigned char addr, unsigned char reg, unsigned char val)
  {
@@ Line 94: / Line 94: @@
    pinMode (myswitch, INPUT_PULLUP);
  }
+ //#define USE_SWITCH
+ #ifdef USE_SWITCH
+ #define DOIT digitalRead (myswitch) == 0
+ #else
+ #define DOIT 1
+ #endif
  void loop (void)
@@ Line 99: / Line 106: @@
    static int r;
-   if (digitalRead (myswitch) == 0) {
+   if (DOIT) {
       setregval (bigrelay, 0x10, 1 << r);
+ #ifdef USE_SWITCH
       delay (10); // debounce
       while (digitalRead (myswitch) == 0)
           /* nothing */ ;
       delay (10); // debounce.
+ #else
+      delay (500);
+ #endif
       r = r + 1;
       if (r == 6) r = 0;

@@ Line 28: / Line 28: @@
 == software ==
+This example uses the BIGRELAY module, and rotates through the six relays each time you press the button.
+(no relays are activated until you first press the button. )
  const int SPICLK  = 13;
@@ Line 34: / Line 37: @@
  const int SPISS  = 10;
  const int myswitch = 9;
  void SPIinit(void)
  {
@@ Line 46: / Line 49: @@
    SPCR    =  _BV(SPE) | _BV(MSTR) | _BV(SPR1) | _BV(SPR0);
  }
  char SPI(char d)
  {  // send character over SPI
@@ Line 55: / Line 58: @@
    return (received);
  }
  void SPI_startpkt (void)
  {
    digitalWrite (SPISS, 0);
  }
  void SPI_endpkt (void)
  {
    digitalWrite (SPISS, 1);
  }
  static unsigned char bigrelay = 0x9c;
  #define WAIT1 25
  #define WAIT2 15
  setregval (unsigned char addr, unsigned char reg, unsigned char val)
  {
@@ Line 83: / Line 86: @@
    SPI_endpkt ();
  }
  void setup (void)
  {
@@ Line 91: / Line 94: @@
    pinMode (myswitch, INPUT_PULLUP);
  }
  void loop (void)
  {
@@ Line 97: / Line 100: @@
    if (digitalRead (myswitch) == 0) {
-      r = r + 1;
-      if (r == 6) r = 0;
       setregval (bigrelay, 0x10, 1 << r);
       delay (10); // debounce
@@ Line 104: / Line 105: @@
           /* nothing */ ;
       delay (10); // debounce.
+      r = r + 1;
+      if (r == 6) r = 0;
    }
  }