diff --git a/firmware/shared/spi.c b/firmware/shared/spi.c
index 0e3954a..2077c82 100644
--- a/firmware/shared/spi.c
+++ b/firmware/shared/spi.c
@@ -8,7 +8,7 @@
 #include "main.h"
 
 
-#include <spi.h>
+#include "spi.h"
 
 /* SPI framework.
  *
diff --git a/firmware/slavechip/Makefile b/firmware/slavechip/Makefile
index aff2bd3..29f0cb2 100644
--- a/firmware/slavechip/Makefile
+++ b/firmware/slavechip/Makefile
@@ -2,7 +2,7 @@ include ../Makefile.inc
 
 COMPILE = avr-gcc $(CFLAGS) $(DEFINES)
 
-OBJECTS = main.o mcp_adc.o i2c_simple.o softtimer.o spi_proto.o spi.o spi_pointers.o
+OBJECTS = main.o mcp_adc.o i2c_simple.o softtimer.o spi_proto.o spi.o spi_pointers.o muxer.o
 
 # symbolic targets:
 all:	firmware.hex
diff --git a/firmware/slavechip/main.c b/firmware/slavechip/main.c
index f1172b2..1088cf1 100644
--- a/firmware/slavechip/main.c
+++ b/firmware/slavechip/main.c
@@ -1,5 +1,6 @@
 #include "main.h"
 #include "spi.h"
+#include "muxer.h"
 
 uint8_t foo;
 uint16_t bar;
@@ -11,6 +12,17 @@ void baz() {
   foo++;
 }
 
+/* pinout
+ * - i2c:
+ *		C5
+ *		C4
+ * - multiplexer:
+ *		C3: inhibit
+ *		C0-C2: muxer select
+ *
+ *
+ * amp 0 is on muxer channel 2
+ */
 
 void hardinit() {
   /* initializes the hardware */
@@ -22,6 +34,8 @@ void hardinit() {
 
   spi_init();
 
+  muxer_init();
+
   sei();
 }
 
diff --git a/firmware/slavechip/muxer.c b/firmware/slavechip/muxer.c
new file mode 100644
index 0000000..53fecd4
--- /dev/null
+++ b/firmware/slavechip/muxer.c
@@ -0,0 +1,16 @@
+#include "muxer.h"
+#include <avr/io.h>
+
+void muxer_init(){
+	DDRC |= (_BV(0)|_BV(1)|_BV(2)|_BV(3)); // conf as outputs
+	PORTC |= _BV(3); // inhibit
+}
+
+void muxer_set(uint8_t channel){
+	PORTC |= _BV(3); // engage inhibit
+	PORTC &= ~(0x07); //mask
+	PORTC |= channel & 0x07; //set 
+	PORTC &= ~(_BV(3)); // disengage inhibit
+	//TODO: delays, check everything, mask in register
+}
+
diff --git a/firmware/slavechip/muxer.h b/firmware/slavechip/muxer.h
new file mode 100644
index 0000000..82d04b3
--- /dev/null
+++ b/firmware/slavechip/muxer.h
@@ -0,0 +1,6 @@
+//TODO:guards
+
+#include <stdint.h>
+
+void muxer_init();
+void muxer_set(uint8_t channel);