1 files changed, 54 insertions, 0 deletions
diff --git a/src/spi_usi.c b/src/spi_usi.c
new file mode 100644
index 0000000..7bdb5c2
--- /dev/null
+++ b/src/spi_usi.c
@@ -0,0 +1,54 @@
+#include "../spi_usi.h"
+#include "../mcu/mcu.h"
+
+#ifdef IOE_SPI_USI_MASTER
+
+// TODO counter settings with interups
+inline void ioe_spi_usi_init(void) {
+    // Set USCK and DO as output
+    DDR_USI |= _BV(DD_USCK) | _BV(DD_DO);
+    // Set DI pull up resistor
+    PORT_USI |= _BV(PORT_DI);
+
+    USICR |= _BV(USIWM0) | _BV(USICS1) | _BV(USICLK);
+}
+
+inline int8_t ioe_spi_usi_transfer(int8_t d) {
+    USISR |= _BV(USIOIF);
+    USIDR = d;
+    do {
+        USICR |= _BV(USITC);
+    } while (!(USISR & _BV(USIOIF)));
+    return USIDR;
+}
+
+#else /* IOE_SPI_USI_MASTER */
+
+inline void ioe_spi_usi_init(void) {
+    // Set DO as output
+    DDR_USI |= _BV(DD_DO);
+    // Set USCK and DI pull up resistor
+    PORT_USI |= _BV(PORT_USCK) | _BV(PORT_DI);
+
+    USICR |= _BV(USIWM0) | _BV(USICS1) | _BV(USIOIE);
+}
+
+inline void ioe_spi_usi_expose(int8_t data) {
+    USIDR = data;
+}
+
+inline uint8_t ioe_spi_usi_busy(void) {
+    return USISR & 0x0F;
+}
+
+inline void ioe_spi_usi_join(void) {
+    while (ioe_spi_usi_busy()) {
+    }
+}
+
+SIGNAL(USI_OVF_vect) {
+    ioe_spi_usi_retrieve(USIDR);
+    USISR |= _BV(USIOIF);
+}
+
+#endif /* IOE_SPI_USI_MASTER */