diff --git a/firmware/spi.c b/firmware/spi.c
index 870a16d..226692a 100644
--- a/firmware/spi.c
+++ b/firmware/spi.c
@@ -38,41 +38,98 @@ void spi_init(){
 		d=7;
 	}
 
-	//TODO: DDRs setzen
+	//DDRs setzen
+#ifdef SPI_MASTER
+	DDRB |= _BV(5) | _BV(3) | _BV(2); //MOSI, SCK, unused SS
+	DDRB &= ~( _BV(4)); //MISO
+	SPI_SSDDR |= _BV(SPI_SS_PIN); // actually used SS
+#else //SPI_MASTER
+	DDRB |= _BV(4); //MISO
+	DDRB &= ~( _BV(5) | _BV(3) | _BV(2)); //MOSI, SCK, SS
+#endif //SPI_MASTER
 	spsr = 0;
 	spsr |=	(d & 1) ? 0 : _BV(SPI2X);
-	spcr = 0 | _BV(SPIE) | _BV(SPE);
+	spcr = 0 | _BV(SPE);
 	spcr |= (d & 2) ? _BV(SPR0) : 0;
 	spcr |= (d & 4) ? _BV(SPR1) : 0;
 
 #ifdef SPI_MASTER
 	spcr |= _BV(MSTR);
 #endif		
-	SPCR = spcr;
 	SPSR = spsr;
+	SPCR = spcr;
+}
+
+void spi_mst_start_packet(){
+	SPI_SSOUT &= ~(_BV(SPI_SS_PIN));
+}
 
-	// initialize interface for ISR:
-	spi_readptr = spi_readbuf;
-	spi_readlen = SPI_READBUF_LEN;
-	spi_writeptr = NULL;
+void spi_mst_end_packet(){
+	SPI_SSOUT |= _BV(SPI_SS_PIN);
 }
 
-// return true on success, false on error
-uint8_t spi_write(uint8_t *data, uint8_t len){
-	if(spi_writeptr != NULL){
-		return 0
+#define SPI_WAIT while(SPSR & _BV(SPIF)){;}
+
+void spi_mst_write(uint8_t len, uint8_t *data){
+	while(len>0){
+		SPDR = *data++;
+		len--;
+		SPI_WAIT;
 	}
-	spi_writeptr = data;
-	spi_writelen = len;
-	//TODO: handle SS, write out first byte
-	return 1;
 }
 
-#ifdef SPI_MASTER
-ISR(SPI_vector){
+void spi_mst_read(uint8_t len, uint8_t *data){
+	while(len>0){
+		SPDR = 0;
+		len--;
+		SPI_WAIT;
+		*data++ = SPDR;
+	}
+}
 
+void spi_sla_handle_packet(){
+	uint8_t opcode, addr, do_write;
+	uint16_t data;
+	SPI_WAIT;
+	SPDR = 0x53; // random ack
+	SPI_WAIT;
+	opcode = SPDR;
+	do_write = spi_proto_needswrite(opcode);
+	SPI_WAIT;
+	addr = SPDR;
+	SPDR = 0x00; // buys some pause
+	if(do_write){
+		data = spi_proto_handlewrite(opcode, addr);
+		SPI_WAIT;
+		SPDR = data >> 8;
+		SPI_WAIT;
+		SPDR = data & 0xff;
+	} else {
+		SPI_WAIT;
+		data = SPDR << 8;
+		SPI_WAIT;
+		data |= SPDR;
+		spi_proto_handleread(opcode, addr, data);
+	}
+}
 
 
+	
+
+	
+
+
+
+
+
+
+
+
+
+#ifndef SPI_MASTER
+ISR(SPI_vector){
 
 }
+
+
 #endif //SPI_MASTER
diff --git a/firmware/spi.h b/firmware/spi.h
index bc9969b..411a1e3 100644
--- a/firmware/spi.h
+++ b/firmware/spi.h
@@ -1,6 +1,21 @@
 #define SPI_BAUDRATE 1000000
 #define SPI_MASTER 1
 #define SPI_READBUF_LEN 32
+#define SPI_SS_PORT D
+#define SPI_SS_PIN 7
+
+
+
+// copied/adapted from usbdrv.h
+#define SPI_CONCAT(a, b)            a ## b
+
+#define SPI_OUTPORT(name)           SPI_CONCAT(PORT, name)
+#define SPI_INPORT(name)            SPI_CONCAT(PIN, name)
+#define SPI_DDRPORT(name)           SPI_CONCAT(DDR, name)
+
+#define SPI_SSOUT SPI_OUTPORT(SPI_SS_PORT)
+#define SPI_SSIN SPI_INPORT(SPI_SS_PORT)
+#define SPI_SSDDR SPI_DDRPORT(SPI_SS_PORT)
 
 uint8_t spi_write(uint8_t *data, uint8_t len);
 void spi_init();