diff --git a/firmware/masterchip/spi_proto.c b/firmware/masterchip/spi_proto.c
deleted file mode 100644
index 923c5ad..0000000
--- a/firmware/masterchip/spi_proto.c
+++ /dev/null
@@ -1,76 +0,0 @@
-#include "spi_proto.h"
-#include "spi.h"
-
-uint8_t read[2];
-uint8_t write[4];
-
-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, 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, SPI_READ_DATA);
-	return (read[0] << 8) | read[1];
-}
-
-uint8_t read_var8(uint8_t number)
-{
-	talk_to_slave(2, number, SPI_READ_DATA);
-	return read[1];
-}
-
-uint16_t read_var16(uint8_t number)
-{
-	talk_to_slave(3, number, SPI_READ_DATA);
-	return (read[0] << 8) | read[1];
-}
-
-void write_var8(uint8_t number, uint8_t value)
-{
-	write[2] = 0;
-	write[3] = number;
-	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, SPI_WRITE_DATA);
-}
-
-void call_func(uint8_t number)
-{
-	talk_to_slave(6, number, SPI_NONE);
-}
diff --git a/firmware/masterchip/spi_proto.c b/firmware/masterchip/spi_proto.c
new file mode 120000
index 0000000..a86d415
--- /dev/null
+++ b/firmware/masterchip/spi_proto.c
@@ -0,0 +1 @@
+../shared/spi_proto.c
\ No newline at end of file
diff --git a/firmware/masterchip/spi_proto.h b/firmware/masterchip/spi_proto.h
deleted file mode 100644
index b425693..0000000
--- a/firmware/masterchip/spi_proto.h
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef SPI_PROTO_H
-#define SPI_PROTO_H
-
-#include <stdint.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);
-void write_var8(uint8_t number, uint8_t value);
-void write_var16(uint8_t number, uint16_t value);
-void call_func(uint8_t number);
-
-#endif
diff --git a/firmware/masterchip/spi_proto.h b/firmware/masterchip/spi_proto.h
new file mode 120000
index 0000000..8d40308
--- /dev/null
+++ b/firmware/masterchip/spi_proto.h
@@ -0,0 +1 @@
+../shared/spi_proto.h
\ No newline at end of file
diff --git a/firmware/shared/spi_proto.c b/firmware/shared/spi_proto.c
new file mode 100644
index 0000000..eb67db8
--- /dev/null
+++ b/firmware/shared/spi_proto.c
@@ -0,0 +1,114 @@
+#include "spi_proto.h"
+#include "spi.h"
+
+/***** MASTER *****/
+
+uint8_t read_data[2];
+uint8_t write_data[4];
+
+void talk_to_slave(uint8_t opcode, uint8_t addr, uint8_t flags)
+{
+	write_data[0] = opcode;
+	write_data[1] = addr;
+	spi_mst_start_packet();
+	spi_mst_write(flags & SPI_WRITE_DATA? 4 : 2, write_data);
+	spi_mst_read(flags & SPI_READ_DATA? 2 : 0, read_data);
+	spi_mst_end_packet();
+}
+
+uint16_t speak_raw(uint8_t opcode, uint8_t number, uint8_t flags, uint16_t value)
+{
+	write_data[2] = value >> 8;
+	write_data[3] = value & 0xff;
+	talk_to_slave(opcode, number, flags);
+	return (read_data[0] << 8) | read_data[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, SPI_READ_DATA);
+	return (read_data[0] << 8) | read_data[1];
+}
+
+uint8_t read_var8(uint8_t number)
+{
+	talk_to_slave(2, number, SPI_READ_DATA);
+	return read_data[1];
+}
+
+uint16_t read_var16(uint8_t number)
+{
+	talk_to_slave(3, number, SPI_READ_DATA);
+	return (read_data[0] << 8) | read_data[1];
+}
+
+void write_var8(uint8_t number, uint8_t value)
+{
+	write_data[2] = 0;
+	write_data[3] = number;
+	talk_to_slave(4, number, SPI_WRITE_DATA);
+}
+
+void write_var16(uint8_t number, uint16_t value)
+{
+	write_data[2] = value >> 8;
+	write_data[3] = value & 0xff;
+	talk_to_slave(5, number, SPI_WRITE_DATA);
+}
+
+void call_func(uint8_t number)
+{
+	talk_to_slave(6, number, SPI_NONE);
+}
+
+
+/***** MASTER END *****/
+/***** SLAVE *****/
+
+
+uint8_t spi_proto_needswrite(uint8_t opcode) {
+  if(opcode == 4 || opcode == 5) return 1;
+  return 0;
+}
+
+uint16_t spi_proto_handlewrite(uint8_t opcode, uint8_t addr) {
+  if(opcode == 4) {
+    return (uint16_t) (*spi_proto_globals8[addr]);
+  } else if(opcode == 5) {
+    return (*spi_proto_globals16[addr]);
+  } else {
+      return 0xFFFF;
+  }
+
+}
+
+void spi_proto_handleread(uint8_t opcode, uint8_t addr, uint16_t data) {
+  if(opcode == 2) {
+    *spi_proto_globals8[addr] = (uint8_t) data;
+  } else if(opcode == 3) {
+    *spi_proto_globals16[addr] = data;
+  } else if (opcode == 6) {
+    funptr_t func = spi_proto_funcs[addr];
+    (*func)();
+  } else {
+    // boom
+  }
+}
+
+/***** SLAVE END *****/
diff --git a/firmware/shared/spi_proto.h b/firmware/shared/spi_proto.h
new file mode 100644
index 0000000..7ff1be8
--- /dev/null
+++ b/firmware/shared/spi_proto.h
@@ -0,0 +1,38 @@
+#ifndef SPI_PROTO_H
+#define SPI_PROTO_H
+
+#include <stdint.h>
+
+/***** MASTER *****/
+
+#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);
+void write_var8(uint8_t number, uint8_t value);
+void write_var16(uint8_t number, uint16_t value);
+void call_func(uint8_t number);
+
+/***** MASTER END *****/
+/***** SLAVE *****/
+
+typedef void(*funptr_t)();
+
+extern uint16_t *spi_proto_globals8[];
+extern uint8_t *spi_proto_globals16[];
+extern funptr_t spi_proto_funcs[];
+
+uint8_t spi_proto_needswrite(uint8_t opcode);
+uint16_t spi_proto_handlewrite(uint8_t opcode, uint8_t addr);
+void spi_proto_handleread(uint8_t opcode, uint8_t addr, uint16_t data);
+
+/***** SLAVE END *****/
+
+#endif
diff --git a/firmware/slavechip/spi_proto.c b/firmware/slavechip/spi_proto.c
deleted file mode 100644
index 2169d1e..0000000
--- a/firmware/slavechip/spi_proto.c
+++ /dev/null
@@ -1,44 +0,0 @@
-#include "spi_proto.h"
-
-
-uint16_t *spi_proto_globals8[] = {
-                                  &foo
-                                 };
-uint8_t *spi_proto_globals16[] = {
-                                  &bar
-                                 };
-funptr_t spi_proto_funcs[] = {
-                             &baz
-                             };
-
-
-
-
-uint8_t spi_proto_needswrite(uint8_t opcode) {
-  if(opcode == 4 || opcode == 5) return 1;
-  return 0;
-}
-
-uint16_t spi_proto_handlewrite(uint8_t opcode, uint8_t addr) {
-  if(opcode == 4) {
-    return (uint16_t) (*spi_proto_globals8[addr]);
-  } else if(opcode == 5) {
-    return (*spi_proto_globals16[addr]);
-  } else {
-      return 0xFFFF;
-  }
-
-}
-
-void spi_proto_handleread(uint8_t opcode, uint8_t addr, uint16_t data) {
-  if(opcode == 2) {
-    *spi_proto_globals8[addr] = (uint8_t) data;
-  } else if(opcode == 3) {
-    *spi_proto_globals16[addr] = data;
-  } else if (opcode == 6) {
-    funptr_t func = spi_proto_funcs[addr];
-    (*func)();
-  } else {
-    // boom
-  }
-}
diff --git a/firmware/slavechip/spi_proto.c b/firmware/slavechip/spi_proto.c
new file mode 120000
index 0000000..a86d415
--- /dev/null
+++ b/firmware/slavechip/spi_proto.c
@@ -0,0 +1 @@
+../shared/spi_proto.c
\ No newline at end of file
diff --git a/firmware/slavechip/spi_proto.h b/firmware/slavechip/spi_proto.h
deleted file mode 100644
index e57f691..0000000
--- a/firmware/slavechip/spi_proto.h
+++ /dev/null
@@ -1,18 +0,0 @@
-#ifndef __SPIPROTO_H
-#define __SPIPROTO_H
-
-#include <stdint.h>
-#include "main.h"
-
-typedef void(*funptr_t)();
-
-
-extern uint16_t *spi_proto_globals8[];
-extern uint8_t *spi_proto_globals16[];
-extern funptr_t spi_proto_funcs[];
-
-uint8_t spi_proto_needswrite(uint8_t opcode);
-uint16_t spi_proto_handlewrite(uint8_t opcode, uint8_t addr);
-void spi_proto_handleread(uint8_t opcode, uint8_t addr, uint16_t data);
-
-#endif
diff --git a/firmware/slavechip/spi_proto.h b/firmware/slavechip/spi_proto.h
new file mode 120000
index 0000000..8d40308
--- /dev/null
+++ b/firmware/slavechip/spi_proto.h
@@ -0,0 +1 @@
+../shared/spi_proto.h
\ No newline at end of file