diff --git a/Inc/utils.h b/Inc/utils.h
deleted file mode 100644
index 1b6f74f..0000000
--- a/Inc/utils.h
+++ /dev/null
@@ -1,10 +0,0 @@
-//
-// Created by MightyPork on 2.9.16.
-//
-
-#ifndef mpork_utils
-#define mpork_utils
-
-void uart_print(const char *string);
-
-#endif
\ No newline at end of file
diff --git a/Src/stm32f1xx_it.c b/Src/stm32f1xx_it.c
index 1404aa9..b965054 100644
--- a/Src/stm32f1xx_it.c
+++ b/Src/stm32f1xx_it.c
@@ -36,8 +36,7 @@
 #include "stm32f1xx_it.h"
 
 /* USER CODE BEGIN 0 */
-#include "utils.h"
-
+#include "debug.h"
 /* USER CODE END 0 */
 
 /* External variables --------------------------------------------------------*/
@@ -94,6 +93,8 @@ prvGetRegistersFromStack(uint32_t *pulFaultStackAddress)
 	pc = pulFaultStackAddress[ 6 ];
 	psr = pulFaultStackAddress[ 7 ];
 
+	error("Hard fault.");
+
 	/* When the following line is hit, the variables contain the register values. */
 	for (;;);
 }
@@ -131,7 +132,7 @@ void HardFault_Handler(void)
 void MemManage_Handler(void)
 {
   /* USER CODE BEGIN MemoryManagement_IRQn 0 */
-  uart_print("MemManage fault.\n");
+  error("MemManage fault.\n");
 
   /* USER CODE END MemoryManagement_IRQn 0 */
   while (1)
@@ -148,7 +149,7 @@ void MemManage_Handler(void)
 void BusFault_Handler(void)
 {
   /* USER CODE BEGIN BusFault_IRQn 0 */
-  uart_print("Bus fault.\n");
+  error("Bus fault.\n");
 
   /* USER CODE END BusFault_IRQn 0 */
   while (1)
@@ -165,7 +166,7 @@ void BusFault_Handler(void)
 void UsageFault_Handler(void)
 {
   /* USER CODE BEGIN UsageFault_IRQn 0 */
-  uart_print("Usage fault.\n");
+  error("Usage fault.\n");
 
   /* USER CODE END UsageFault_IRQn 0 */
   while (1)
diff --git a/Src/utils.c b/Src/utils.c
deleted file mode 100644
index 4a1d068..0000000
--- a/Src/utils.c
+++ /dev/null
@@ -1,19 +0,0 @@
-//
-// Created by MightyPork on 2.9.16.
-//
-
-#include <string.h>
-#include "stm32f1xx_hal_conf.h"
-#include "adc.h"
-#include "tim.h"
-#include "usart.h"
-#include "utils.h"
-
-void uart_print(const char *string)
-{
-	HAL_UART_Transmit(&huart1, (char*)string, (uint16_t) strlen(string), 10);
-
-	// Stop ADC and the timer
-	HAL_ADC_Stop(&hadc1);
-	HAL_TIM_Base_Stop(&htim3);
-}
\ No newline at end of file
diff --git a/User/debug.c b/User/debug.c
new file mode 100644
index 0000000..e98b870
--- /dev/null
+++ b/User/debug.c
@@ -0,0 +1,119 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <inttypes.h>
+#include "debug.h"
+#include "timebase.h"
+
+
+void dbg_printf(const char *fmt, ...)
+{
+	va_list va;
+	va_start(va, fmt);
+	vprintf(fmt, va);
+	va_end(va);
+}
+
+void dbg_va_base(const char *fmt, const char *tag, va_list va)
+{
+	ms_time_t now = ms_now();
+	uint32_t secs = now / 1000;
+	uint32_t ms = now % 1000;
+
+	printf("%4"PRIu32".%03"PRIu32" ", secs, ms);
+
+	dbg_raw(tag);
+
+	vprintf(fmt, va);
+	dbg_raw(DEBUG_EOL);
+}
+
+/** Print a log message with a DEBUG tag and newline */
+void dbg(const char *fmt, ...)
+{
+	va_list va;
+	va_start(va, fmt);
+	dbg_va_base(fmt, DEBUG_TAG_BASE, va);
+	va_end(va);
+}
+
+
+/** Print a log message with an INFO tag and newline */
+void info(const char *fmt, ...)
+{
+	v100_attr(FMT_WHITE);
+
+	va_list va;
+	va_start(va, fmt);
+	dbg_va_base(fmt, DEBUG_TAG_INFO, va);
+	va_end(va);
+
+	v100_attr(FMT_RESET);
+}
+
+
+
+/** Print a log message with an INFO tag and newline */
+void banner(const char *fmt, ...)
+{
+	v100_attr(FMT_GREEN, FMT_BRIGHT);
+
+	va_list va;
+	va_start(va, fmt);
+	dbg_va_base(fmt, DEBUG_TAG_INFO, va);
+	va_end(va);
+
+	v100_attr(FMT_RESET);
+}
+
+
+/** Print a log message with a warning tag and newline */
+void warn(const char *fmt, ...)
+{
+	v100_attr(FMT_YELLOW, FMT_BRIGHT);
+
+	va_list va;
+	va_start(va, fmt);
+	dbg_va_base(fmt, DEBUG_TAG_WARN, va);
+	va_end(va);
+
+	v100_attr(FMT_RESET);
+}
+
+
+/** Print a log message with an ERROR tag and newline */
+void error(const char *fmt, ...)
+{
+	v100_attr(FMT_RED, FMT_BRIGHT);
+
+	va_list va;
+	va_start(va, fmt);
+	dbg_va_base(fmt, DEBUG_TAG_ERROR, va);
+	va_end(va);
+
+	v100_attr(FMT_RESET);
+}
+
+
+void v100_attr_(uint8_t count, ...)
+{
+	va_list va;
+	va_start(va, count);
+
+	putchar(27);
+	putchar('[');
+
+	for (int i = 0; i < count; i++) {
+		int attr = va_arg(va, int);
+
+		// comma
+		if (i > 0) putchar(';');
+
+		// number
+		printf("%d", attr);
+	}
+
+	putchar('m');
+
+	va_end(va);
+}
diff --git a/User/debug.h b/User/debug.h
new file mode 100644
index 0000000..5343ac5
--- /dev/null
+++ b/User/debug.h
@@ -0,0 +1,95 @@
+#pragma once
+
+#include <stdlib.h>
+#include <stdarg.h>
+
+// helper to mark printf functions
+#define PRINTF_LIKE __attribute__((format(printf, 1, 2)))
+
+// formatting symbols
+#define DEBUG_EOL "\r\n"
+#define DEBUG_TAG_WARN  "[W] "
+#define DEBUG_TAG_ERROR "[E] "
+#define DEBUG_TAG_BASE  "[ ] "
+#define DEBUG_TAG_INFO  "[i] "
+
+
+/** Print a log message with no tag and no newline */
+void dbg_printf(const char *fmt, ...) PRINTF_LIKE;
+
+/** Print via va_list */
+void dbg_va_base(const char *fmt, const char *tag, va_list va);
+
+/** Print a string to the debug interface (length not limited) */
+static inline void dbg_raw(const char *str)
+{
+	fputs(str, stdout);
+}
+
+
+/** Print a char to the debug interface */
+static inline void dbg_raw_c(char c)
+{
+	putchar((uint8_t) c);
+}
+
+/** Print a log message with a "debug" tag and newline */
+void dbg(const char *fmt, ...) PRINTF_LIKE;
+
+/** Print a log message with an "info" tag and newline */
+void info(const char *fmt, ...) PRINTF_LIKE;
+
+/** Print a log message with a "banner" tag and newline */
+void banner(const char *fmt, ...) PRINTF_LIKE;
+
+/** Print a log message with a "warning" tag and newline */
+void warn(const char *fmt, ...) PRINTF_LIKE;
+
+
+/** Print a log message with an "error" tag and newline */
+void error(const char *fmt, ...) PRINTF_LIKE;
+
+
+/** ANSI formatting attributes */
+typedef enum {
+	// Non-colour Attributes
+	FMT_RESET = 0, // Reset all attributes
+	FMT_BRIGHT = 1, // Bright
+	FMT_DIM = 2, // Dim
+	FMT_UNDER = 4, // Underscore
+	FMT_BLINK = 5, // Blink
+	FMT_INVERS = 7, // Reverse
+	FMT_HIDDEN = 8, // Hidden
+	FMT_ITALIC = 16, // Italic font
+	FMT_FAINT = 32, // Faint color
+
+	// Foreground Colours
+	FMT_BLACK = 30, // Black
+	FMT_RED = 31, // Red
+	FMT_GREEN = 32, // Green
+	FMT_YELLOW = 33, // Yellow
+	FMT_BLUE = 34, // Blue
+	FMT_MAGENTA = 35, // Magenta
+	FMT_CYAN = 36, // Cyan
+	FMT_WHITE = 37, // White
+
+	// Background Colours
+	FMT_BLACK_BG = 40, // Black
+	FMT_RED_BG = 41, // Red
+	FMT_GREEN_BG = 42, // Green
+	FMT_YELLOW_BG = 43, // Yellow
+	FMT_BLUE_BG = 44, // Blue
+	FMT_MAGENTA_BG = 45, // Magenta
+	FMT_CYAN_BG = 46, // Cyan
+	FMT_WHITE_BG = 47, // White
+} ANSI_attr_t;
+
+#define VA_NUM_ARGS(...) VA_NUM_ARGS_IMPL(__VA_ARGS__, 5,4,3,2,1)
+#define VA_NUM_ARGS_IMPL(_1, _2, _3, _4, _5, N, ...) N
+
+#define v100_attr(...) v100_attr_(VA_NUM_ARGS(__VA_ARGS__), __VA_ARGS__)
+
+/**
+ * Send formatting code to a com interface
+ */
+void v100_attr_(uint8_t count, ...);
diff --git a/User/dotmatrix.c b/User/dotmatrix.c
index fe848e4..2300287 100644
--- a/User/dotmatrix.c
+++ b/User/dotmatrix.c
@@ -1,6 +1,5 @@
 #include <string.h>
 #include <stdbool.h>
-#include <utils.h>
 #include "dotmatrix.h"
 #include "malloc_safe.h"
 
diff --git a/User/syscalls.c b/User/syscalls.c
index 72cb6be..1f790fb 100644
--- a/User/syscalls.c
+++ b/User/syscalls.c
@@ -1,7 +1,9 @@
 #include <errno.h>
 #include <stdio.h>
+#include <usart.h>
+#include <sys/stat.h>
 
-register char * stack_ptr asm("sp");
+register char *stack_ptr asm("sp");
 
 caddr_t _sbrk(int incr)
 {
@@ -13,8 +15,7 @@ caddr_t _sbrk(int incr)
 		heap_end = &end;
 
 	prev_heap_end = heap_end;
-	if (heap_end + incr > stack_ptr)
-	{
+	if (heap_end + incr > stack_ptr) {
 //		write(1, "Heap and stack collision\n", 25);
 //		abort();
 		errno = ENOMEM;
@@ -27,6 +28,56 @@ caddr_t _sbrk(int incr)
 }
 
 
-// Other systcalls are defined in
-// - com/com_fileio.c
-// - hw_utils/reset.h
+/**
+ * @brief Write to a file by file descriptor.
+ *
+ * @param fd  : open file descriptor
+ * @param buf : data to write
+ * @param len : buffer size
+ * @return number of written bytes
+ */
+int _write(int fd, const char *buf, int len)
+{
+	switch (fd) {
+		case 1: // stdout
+		case 2: // stderr
+			HAL_UART_Transmit(&huart1, (uint8_t*)buf, len, 10);
+			return len;
+
+		default:
+			return 0;
+	}
+}
+
+// region stubs
+
+int _read(int fd, char *buf, int len)
+{
+	return 0;
+}
+
+int _fstat(int file, struct stat *st)
+{
+	st->st_mode = S_IFCHR;
+	return 0;
+}
+
+int _lseek(int file, int ptr, int dir)
+{
+	return 0;
+}
+
+int _close(int file)
+{
+	return -1;
+}
+
+int _isatty(int fd)
+{
+	if (fd == 0 || fd == 1 || fd == 2)
+		return 1;
+	else
+		return 0;
+}
+
+// endregion
\ No newline at end of file
diff --git a/User/timebase.c b/User/timebase.c
index 55ce4b4..0ffee7d 100644
--- a/User/timebase.c
+++ b/User/timebase.c
@@ -1,5 +1,6 @@
 #include "timebase.h"
 #include "malloc_safe.h"
+#include "debug.h"
 
 // Time base
 static volatile ms_time_t SystemTime_ms = 0;
@@ -87,8 +88,7 @@ static periodic_task_t* claim_periodic_task_slot(ms_time_t interval, bool enqueu
 		return task;
 	}
 
-	// TODO logging
-	//error("Periodic task table full.");
+	error("Periodic task table full.");
 
 	return NULL;
 }
diff --git a/User/user_main.c b/User/user_main.c
index e445955..95fcee9 100644
--- a/User/user_main.c
+++ b/User/user_main.c
@@ -9,11 +9,11 @@
 #include "dotmatrix.h"
 #include "mxconstants.h"
 #include "stm32f1xx_hal.h"
-#include "utils.h"
 #include "adc.h"
 #include "tim.h"
 #include "user_main.h"
 #include "debounce.h"
+#include "debug.h"
 
 #define SAMPLE_COUNT 256
 #define BIN_COUNT (SAMPLE_COUNT/2)
@@ -160,12 +160,7 @@ void HAL_SYSTICK_Callback(void)
 
 static void gamepad_button_press(uint32_t btn)
 {
-	uart_print("Button press ");
-	char x[2];
-	x[0] = '0' + btn;
-	x[1] = 0;
-	uart_print(x);
-	uart_print("\n");
+	dbg("Button press %d", btn);
 }
 
 void user_init() {
@@ -225,7 +220,9 @@ void user_init() {
 
 void user_main()
 {
-	uart_print("== USER CODE STARTING ==\n");
+	banner("== USER CODE STARTING ==");
+
+	info("Hello world");
 
 	user_init();
 
@@ -247,7 +244,7 @@ void user_main()
 
 void user_Error_Handler()
 {
-	uart_print("HAL error occurred.\n");
+	error("HAL error occurred.\n");
 	while (1);
 }
 
@@ -265,16 +262,7 @@ void user_assert_failed(uint8_t *file, uint32_t line)
 
 void user_error_file_line(const char *message, const char *file, uint32_t line)
 {
-	uart_print(message);
-	uart_print(" in file ");
-	uart_print((char *) file);
-	uart_print(" on line ");
-
-	char x[10];
-	sprintf(x, "%"PRIu32, line);
-	uart_print(x);
-	uart_print("\n");
-
+	error("%s in file %s on line %d", message, file, line);
 	while (1);
 }