1 files changed, 39 insertions, 0 deletions
diff --git a/spi.c b/spi.c
new file mode 100644
index 0000000..623f5d1
--- /dev/null
+++ b/spi.c
@@ -0,0 +1,39 @@
+#include <stdint.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include "spi.h"
+
+void spi_init()
+{
+    DDR_SPI &= ~((1<<DD_MOSI)|(1<<DD_MISO)|(1<<DD_SS)|(1<<DD_SCK));
+    DDR_SPI |= ((1<<DD_MOSI)|(1<<DD_SS)|(1<<DD_SCK));
+
+    SPCR = ((1<<SPE)|               // SPI Enable
+            (0<<SPIE)|              // SPI Interupt Enable
+            (0<<DORD)|              // Data Order (0:MSB first / 1:LSB first)
+            (1<<MSTR)|              // Master/Slave select
+            (1<<SPR1)|(1<<SPR0)|    // SPI Clock Rate
+            (0<<CPOL)|              // Clock Polarity (0:SCK low / 1:SCK hi when idle)
+            (0<<CPHA));             // Clock Phase (0:leading / 1:trailing edge sampling)
+
+    SPSR = (0<<SPIF)|(0<<WCOL)|(0<<SPI2X);              // Double Clock Rate
+}
+
+uint8_t spi_fast_shift(uint8_t data)
+{
+  SPDR = data;
+  while((SPSR & (1<<SPIF))==0);
+  return SPDR;
+}
+
+uint8_t spi_two_byte(uint8_t cmd, uint8_t arg)
+{
+  uint8_t data_buf;
+
+  spi_cs_low();
+  spi_fast_shift(cmd);
+  data_buf = spi_fast_shift(arg);
+  spi_cs_high();
+
+  return data_buf;
+}