diff --git a/log.h b/log.h
new file mode 100644
index 0000000..061df1c
--- /dev/null
+++ b/log.h
@@ -0,0 +1,36 @@
+/* log.h */
+
+#ifndef __LOG_H
+#define __LOG_H
+
+#include "types.h"
+
+char log_get_byte(void);
+void log_put_byte(char c);
+void log_put_uint16(unsigned int i);
+void log_put_uint(unsigned int i);
+void log_put_float(float f);
+void log_put_header(unsigned int timestamp);
+void log_put_array(char *data, int length);
+
+void log_mark_busy(void);
+void log_mark_idle(void);
+unsigned int log_read_busytime(void);
+
+/* Needed by log.c and sdcard.c only */
+#define LOG_MAGIC 0x00000CFC
+
+#define LOG_BUFFERSIZE 4096
+
+extern unsigned int log_bufferstart;
+extern unsigned int log_bufferend;
+extern bool log_enabled;
+extern char log_buffer[];
+
+extern unsigned int log_generation;
+
+#define LOG_BUFFER_EMPTY (log_bufferstart == log_bufferend)
+#define LOG_BUFFER_BYTES ((log_bufferend - log_bufferstart) % \
+                                LOG_BUFFERSIZE)
+
+#endif /* __LOG_H */
diff --git a/mpu6050.h b/mpu6050.h
new file mode 100644
index 0000000..31676d3
--- /dev/null
+++ b/mpu6050.h
@@ -0,0 +1,15 @@
+#ifndef __MPU6050_H
+#define __MPU6050_H
+
+#include "types.h"
+
+bool mpu6050_init(void);
+bool mpu6050_start_sample(void);
+void mpu6050_start_zero(void);
+void mpu6050_write_log(void);
+
+#if 0
+bool mpu6050_sample(void);
+#endif
+
+#endif /* __MPU6050_H */
diff --git a/sdcard.h b/sdcard.h
new file mode 100644
index 0000000..df0dde9
--- /dev/null
+++ b/sdcard.h
@@ -0,0 +1,12 @@
+/* sdcard.h */
+
+#ifndef __SDCARD_H
+#define __SDCARD_H
+
+#include "types.h"
+
+bool init_sdcard(void);
+bool sdcard_read(unsigned int address, char *buffer, unsigned int length);
+void sdcard_poll(void);
+
+#endif /* __SDCARD_H */
diff --git a/spi.h b/spi.h
new file mode 100644
index 0000000..51e96a8
--- /dev/null
+++ b/spi.h
@@ -0,0 +1,19 @@
+/* spi.h */
+
+#ifndef __SPI_H
+#define __SPI_H
+
+#include "types.h"
+
+void init_spi(void);
+void spi_speedup(void);
+void spi_write_byte(char byte);
+char spi_read_byte(void);
+void spi_write_bytes(char *data, int len);
+void spi_read_bytes(char *data, int len);
+void spi_transaction_start(void);
+void spi_transaction_stop(void);
+void spi_drain(void);
+
+
+#endif /* __SPI_H */
diff --git a/wmp.h b/wmp.h
deleted file mode 100644
index f71ed19..0000000
--- a/wmp.h
+++ /dev/null
@@ -1,25 +0,0 @@
-#ifndef __WMP_H
-#define __WMP_H
-
-#include "types.h"
-
-extern unsigned int wmp_yaw;
-extern unsigned int wmp_pitch;
-extern unsigned int wmp_roll;
-
-extern unsigned char wmp_calibration_data[];
-
-extern bool wmp_yaw_fast;
-extern bool wmp_pitch_fast;
-extern bool wmp_roll_fast;
-
-extern bool wmp_zero;
-
-bool wmp_init(void);
-bool wmp_sample(void);
-bool wmp_read_calibration_data(void);
-bool wmp_start_sample(void);
-void wmp_event_handler(void);
-void wmp_start_zero(void);
-
-#endif /* __WMP_H */