diff --git a/firmware/masterchip/Makefile b/firmware/masterchip/Makefile
index 087798e..c5d5e81 100644
--- a/firmware/masterchip/Makefile
+++ b/firmware/masterchip/Makefile
@@ -3,7 +3,7 @@ include ../Makefile.inc
 
 COMPILE = avr-gcc $(CFLAGS) $(DEFINES)
 
-OBJECTS = usbdrv/usbdrvasm.o usbdrv/usbdrv.o main.o display.o lcd/lcd.o usb.o softtimer.o
+OBJECTS = usbdrv/usbdrvasm.o usbdrv/usbdrv.o main.o display.o lcd/lcd.o usb.o softtimer.o spi.o spi_proto.o
 
 # symbolic targets:
 all:	firmware.hex
diff --git a/firmware/masterchip/spi_proto.c b/firmware/masterchip/spi_proto.c
index c12e128..923c5ad 100644
--- a/firmware/masterchip/spi_proto.c
+++ b/firmware/masterchip/spi_proto.c
@@ -4,31 +4,55 @@
 uint8_t read[2];
 uint8_t write[4];
 
-void talk_to_slave(uint8_t opcode, uint8_t addr, uint8_t wlen, uint8_t rlen)
+void talk_to_slave(uint8_t opcode, uint8_t addr, uint8_t flags)
 {
 	write[0] = opcode;
 	write[1] = addr;
 	spi_mst_start_packet();
-	spi_mst_write(wlen, write);
-	spi_mst_read(rlen, read);
+	spi_mst_write(wlen, flags & SPI_WRITE_DATA? 4 : 2);
+	spi_mst_read(rlen, flags & SPI_READ_DATA? 2 : 0);
 	spi_mst_end_packet();
 }
 
+uint16_t speak_raw(uint8_t opcode, uint8_t number, uint8_t flags, uint16_t value)
+{
+	write[2] = value >> 8;
+	write[3] = value & 0xff;
+	talk_to_slave(opcode, number, flags);
+	return (read[0] << 8) | read[1];
+}
+
+uint8_t spi_proto_needs(uint8_t opcode)
+{
+	uint8_t r = SPI_NONE;
+	switch(opcode)
+	{
+		case 1: case 2: case 3:
+			r = SPI_READ_DATA;
+			break;
+		case 4: case 5:
+			r = SPI_WRITE_DATA;
+			break;
+	}
+	return r;
+}
+
+
 uint16_t read_temperature(uint8_t number)
 {
-	talk_to_slave(1, number, 2, 2);
+	talk_to_slave(1, number, SPI_READ_DATA);
 	return (read[0] << 8) | read[1];
 }
 
 uint8_t read_var8(uint8_t number)
 {
-	talk_to_slave(2, number, 2, 2);
+	talk_to_slave(2, number, SPI_READ_DATA);
 	return read[1];
 }
 
 uint16_t read_var16(uint8_t number)
 {
-	talk_to_slave(3, number, 2, 2);
+	talk_to_slave(3, number, SPI_READ_DATA);
 	return (read[0] << 8) | read[1];
 }
 
@@ -36,17 +60,17 @@ void write_var8(uint8_t number, uint8_t value)
 {
 	write[2] = 0;
 	write[3] = number;
-	talk_to_slave(4, number, 4, 0);
+	talk_to_slave(4, number, SPI_WRITE_DATA);
 }
 
 void write_var16(uint8_t number, uint16_t value)
 {
 	write[2] = value >> 8;
 	write[3] = value & 0xff;
-	talk_to_slave(5, number, 4, 0);
+	talk_to_slave(5, number, SPI_WRITE_DATA);
 }
 
 void call_func(uint8_t number)
 {
-	talk_to_slave(6, number, 2, 0);
+	talk_to_slave(6, number, SPI_NONE);
 }
diff --git a/firmware/masterchip/spi_proto.h b/firmware/masterchip/spi_proto.h
index c7861fc..93d0dfa 100644
--- a/firmware/masterchip/spi_proto.h
+++ b/firmware/masterchip/spi_proto.h
@@ -1,6 +1,14 @@
 #ifndef SPI_PROTO_H
 #define SPI_PROTO_H
 
+#define SPI_WRITE_DATA 0x01
+#define SPI_READ_DATA 0x10
+#define SPI_NONE 0
+
+uint16_t speak_raw(uint8_t opcode, uint8_t number, uint8_t flags, uint16_t data);
+
+uint8_t spi_proto_needs(uint8_t opcode);
+
 uint16_t read_temperature(uint8_t number);
 uint8_t read_var8(uint8_t number);
 uint16_t read_var16(uint8_t number);
diff --git a/firmware/masterchip/usb.c b/firmware/masterchip/usb.c
index 5c9ed9e..fc68300 100644
--- a/firmware/masterchip/usb.c
+++ b/firmware/masterchip/usb.c
@@ -27,13 +27,11 @@ usbMsgLen_t usbFunctionSetup(uchar data[8]) {
     uint8_t valH =   (uint8_t)    rq->wIndex.bytes[0];
     uint8_t valL =   (uint8_t)    rq->wIndex.bytes[1];
 
-    uint8_t send[] = {opcode, addr, valH, valL};
-    uint8_t recv[2];
-    spi_mst_write(4, send);
-    if(!spi_proto_needswrite(opcode)) spi_mst_read(2, recv);
-      
-    dataBuffer[0] = recv[0];
-    dataBuffer[1] = recv[1];
+    uint16_t send = (valH << 8) | valL;
+    uint16_t recv = speak_raw(opcode, addr, spi_proto_needs(opcode), send);
+    
+    dataBuffer[0] = (recv >> 8) & 0xff;
+    dataBuffer[1] = recv & 0xff;
     dataBuffer[2] = 0x0000;
     dataBuffer[3] = 0x0000;
     usbMsgPtr = dataBuffer;