Platform specific code for a robot using stepper motors.

platform/stepper-robot/sam7s-spi.c

@@ -0,0 +1,126 @@
+#include <AT91SAM7S64.h>
+#include <stdint.h>
+#include <dev/spi.h>
+#include <sam7s-spi.h>
+
+/* Prevents interrupts using SPI at inappropriate times */
+unsigned char spi_busy = 0;
+
+#define SPI_SPEED 1000000  /* 1MHz clock*/
+#define SPI_DLYBCT 1
+#define SPI_DLYBS 20
+
+#define SPI_TRANSFER (AT91C_PA12_MISO | AT91C_PA13_MOSI | AT91C_PA14_SPCK)
+
+#define SPI_CS (AT91C_PA11_NPCS0 | AT91C_PA31_NPCS1)
+
+void
+spi_init()
+{
+  static uint8_t initialised = 0;
+  if (!initialised) {
+    *AT91C_SPI_CR = AT91C_SPI_SPIDIS | AT91C_SPI_SWRST;
+    *AT91C_PMC_PCER = (1 << AT91C_ID_SPI);
+    *AT91C_PIOA_ASR = SPI_TRANSFER | SPI_CS;
+    *AT91C_PIOA_PDR = SPI_TRANSFER | SPI_CS;
+    *AT91C_PIOA_PPUER = AT91C_PA12_MISO | SPI_CS;
+    *AT91C_SPI_MR = (AT91C_SPI_MSTR | AT91C_SPI_PS_FIXED
+		     | AT91C_SPI_MODFDIS | AT91C_SPI_PCS);
+
+    /* It seems necessary to set the clock speed for chip select 0
+       even if it's not used. */
+    AT91C_SPI_CSR[0] = (MCK/SPI_SPEED)<<8;
+
+    *AT91C_SPI_CR = AT91C_SPI_SPIEN;
+    initialised = 1;
+  }
+}
+
+void
+spi_init_chip_select(unsigned int chip, unsigned int speed,
+		     unsigned int dlybct,
+		     unsigned int dlybs, unsigned int phase,
+		     unsigned int polarity)
+{
+  spi_init();
+
+  AT91C_SPI_CSR[chip] =
+    ((dlybct<<24) | (dlybs<<16) | (((MCK+speed/2)/speed)<<8)
+     | (phase?AT91C_SPI_NCPHA:0) | (polarity?AT91C_SPI_CPOL:0)
+     | AT91C_SPI_BITS_8 | AT91C_SPI_CSAAT);
+}
+
+#if 0
+#define DBG_SEND dbg_blocking_putchar('>');
+#define DBG_RECV dbg_blocking_putchar('<');
+#else
+#define DBG_SEND
+#define DBG_RECV
+#endif
+
+void
+spi_transfer(unsigned int chip, const struct spi_block *block, unsigned int blocks)
+{
+  spi_busy = 1;
+  while(!(*AT91C_SPI_SR & AT91C_SPI_TXEMPTY)); /* wait unti previous transfer is done */
+  
+  /* Clear any data left in the receiver */
+  (void)*AT91C_SPI_RDR;
+  (void)*AT91C_SPI_RDR;
+
+  /* Select chip */
+  *AT91C_SPI_MR = ((*AT91C_SPI_MR & ~AT91C_SPI_PCS)
+		   | ((~(1<<chip) & 0x0f) << 16));
+  
+  while(blocks-- > 0) {
+    struct spi_block current = *block++;
+    if (current.send) {
+      if (current.receive) {
+	/* Send and receive */
+	while(current.len-- > 0) {
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_TDRE));
+	  *AT91C_SPI_TDR = *current.send++;
+	  DBG_SEND;
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_RDRF));
+	  *current.receive++ = *AT91C_SPI_RDR;
+	  DBG_RECV;
+	}
+      } else {
+	/* Send only */
+	while(current.len-- > 0) {
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_TDRE));
+	  *AT91C_SPI_TDR = *current.send++;
+	  DBG_SEND;
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_RDRF));
+	  (void)*AT91C_SPI_RDR;
+	  DBG_RECV;
+	}
+      }
+    } else {
+      if (current.receive) {
+	/* Receive only */
+	while(current.len-- > 0) {
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_TDRE));
+	  *AT91C_SPI_TDR = 0;
+	  DBG_SEND;
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_RDRF));
+	  *current.receive++ = *AT91C_SPI_RDR;
+	  DBG_RECV;
+	}
+      } else {
+	/* Clock only */
+	while(current.len-- > 0) {
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_TDRE));
+	  *AT91C_SPI_TDR = 0;
+	  DBG_SEND;
+	  while(!(*AT91C_SPI_SR & AT91C_SPI_RDRF));
+	  (void)*AT91C_SPI_RDR;
+	  DBG_RECV;
+	}
+      }
+    } 
+  }
+  *AT91C_SPI_CR = AT91C_SPI_LASTXFER;
+    
+  spi_busy = 0;
+}