diff --git a/printf/compat.h b/printf/compat.h
new file mode 100644
index 0000000..93e0a2f
--- /dev/null
+++ b/printf/compat.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#ifndef offsetof
+#define offsetof(type, member)  __builtin_offsetof (type, member)
+#endif
+
+#ifndef bool
+#define bool int
+#endif
+
+#ifndef false
+#define false 0
+#endif
+
+#ifndef true
+#define true 1
+#endif
+
+#ifndef static_assert
+#define static_assert(s) _Static_assert(s, "");
+#endif
+
+#ifndef nullptr
+#define nullptr ((void *)0)
+#endif
diff --git a/printf/minmax.h b/printf/minmax.h
new file mode 100644
index 0000000..df4c506
--- /dev/null
+++ b/printf/minmax.h
@@ -0,0 +1,4 @@
+#pragma once
+
+#define min(a, b) ( (a < b) ? a : b )
+#define max(a, b) ( (a > b) ? a : b )
diff --git a/printf/parse.c b/printf/parse.c
new file mode 100644
index 0000000..46b9b9c
--- /dev/null
+++ b/printf/parse.c
@@ -0,0 +1,70 @@
+#include <stddef.h>
+
+#include "parse.h"
+
+int parse_base10_digit(char c)
+{
+  switch (c) {
+  case '0': return 0;
+  case '1': return 1;
+  case '2': return 2;
+  case '3': return 3;
+  case '4': return 4;
+  case '5': return 5;
+  case '6': return 6;
+  case '7': return 7;
+  case '8': return 8;
+  case '9': return 9;
+  default: return -1;
+  }
+}
+
+const char * parse_base10(const char * s, int * n)
+{
+  *n = 0;
+  int sign = 1;
+
+  if (*s == '-') {
+    sign = -1;
+    s++;
+  }
+
+  while (true) {
+    int digit = parse_base10_digit(*s);
+    if (digit == -1)
+      break;
+
+    *n *= 10;
+    *n += digit;
+    s++;
+  }
+
+  *n *= sign;
+
+  return s;
+}
+
+const char * parse_base10_64(const char * s, int64_t * n)
+{
+  *n = 0;
+  int sign = 1;
+
+  if (*s == '-') {
+    sign = -1;
+    s++;
+  }
+
+  while (true) {
+    int digit = parse_base10_digit(*s);
+    if (digit == -1)
+      break;
+
+    *n *= 10;
+    *n += digit;
+    s++;
+  }
+
+  *n *= sign;
+
+  return s;
+}
diff --git a/printf/parse.h b/printf/parse.h
new file mode 100644
index 0000000..022b84c
--- /dev/null
+++ b/printf/parse.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stdint.h>
+#include "compat.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+const char * parse_skip(const char * s, char c);
+const char * parse_find(const char * s, char c);
+const char * parse_find_first_right(const char * s, int length, char c);
+int parse_base10_digit(char c);
+const char * parse_base10(const char * s, int * n);
+const char * parse_base10_64(const char * s, int64_t * n);
+const char * parse_match(const char * s, const char * m);
+int parse_stride(const char * s, int length);
+int parse_height(const char * s, int length);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/printf/printf.c b/printf/printf.c
new file mode 100644
index 0000000..9341162
--- /dev/null
+++ b/printf/printf.c
@@ -0,0 +1,186 @@
+#include <stdint.h>
+#include <stdarg.h>
+
+#include "parse.h"
+#include "unparse.h"
+#include "printf.h"
+//#include "sh7091_scif.h"
+
+enum format_type {
+  FORMAT_BASE10_UNSIGNED,
+  FORMAT_BASE10,
+  FORMAT_BASE10_64,
+  FORMAT_POINTER,
+  FORMAT_BASE16,
+  FORMAT_STRING,
+  FORMAT_CHAR,
+  FORMAT_PERCENT,
+};
+
+struct format {
+  enum format_type type;
+  int pad_length;
+  char fill_char;
+};
+
+static const char * parse_escape(const char * format, struct format * ft);
+
+static const char * parse_fill_pad(const char * format, struct format * ft)
+{
+  if (*format == 0)
+    return format;
+  if (*format >= '1' && *format <= '9')
+    ft->fill_char = ' ';
+  else
+    ft->fill_char = *format++;
+  format = parse_base10(format, &ft->pad_length);
+  return parse_escape(format, ft);
+}
+
+static const char * parse_escape(const char * format, struct format * ft)
+{
+  switch (*format) {
+  case 0:
+    return format;
+  case 'u':
+    ft->type = FORMAT_BASE10_UNSIGNED;
+    return format + 1;
+  case 'd':
+    ft->type = FORMAT_BASE10;
+    return format + 1;
+  case 'l':
+    ft->type = FORMAT_BASE10_64;
+    return format + 1;
+  case 'p':
+    ft->type = FORMAT_POINTER;
+    return format + 1;
+  case 'x':
+    ft->type = FORMAT_BASE16;
+    return format + 1;
+  case 's':
+    ft->type = FORMAT_STRING;
+    return format + 1;
+  case 'c':
+    ft->type = FORMAT_CHAR;
+    return format + 1;
+  case '%':
+    ft->type = FORMAT_PERCENT;
+    return format + 1;
+  default:
+    return parse_fill_pad(format, ft);
+  }
+}
+
+void print_string(const char * s, int length)
+{
+  for (int i = 0; i < length; i++) {
+    print_char(s[i]);
+  }
+}
+
+void print_bytes(const uint8_t * s, int length)
+{
+  for (int i = 0; i < length; i++) {
+    print_char(s[i]);
+  }
+}
+
+void print_chars(const uint16_t * s, int length)
+{
+  for (int i = 0; i < length; i++) {
+    print_char(s[i]);
+  }
+}
+
+void print_cstring(const char * s)
+{
+  while (*s != 0) {
+    print_char(*s++);
+  }
+}
+
+void _printf(const char * format, ...)
+{
+  va_list args;
+  va_start(args, format);
+
+  while (true) {
+    if (*format == 0)
+      break;
+
+    switch (*format) {
+    case '%':
+      {
+        struct format ft = {0};
+        format = parse_escape(format + 1, &ft);
+        switch (ft.type) {
+        case FORMAT_BASE10_UNSIGNED:
+          {
+            uint32_t num = va_arg(args, uint32_t);
+            char s[10];
+            int offset = unparse_base10_unsigned(s, num, ft.pad_length, ft.fill_char);
+            print_string(s, offset);
+          }
+          break;
+        case FORMAT_BASE10:
+          {
+            int32_t num = va_arg(args, int32_t);
+            char s[10];
+            int offset = unparse_base10(s, num, ft.pad_length, ft.fill_char);
+            print_string(s, offset);
+          }
+          break;
+        case FORMAT_BASE10_64:
+          {
+            int64_t num = va_arg(args, int64_t);
+            char s[20];
+            int offset = unparse_base10_64(s, num, ft.pad_length, ft.fill_char);
+            print_string(s, offset);
+          }
+          break;
+        case FORMAT_POINTER:
+          {
+            print_char('0');
+            print_char('x');
+          }
+          [[fallthrough]];
+        case FORMAT_BASE16:
+          {
+            uint32_t num = va_arg(args, uint32_t);
+            char s[8];
+            int offset = unparse_base16(s, num, ft.pad_length, ft.fill_char);
+            print_string(s, offset);
+          }
+          break;
+        case FORMAT_STRING:
+          {
+            const char * s = va_arg(args, const char *);
+            while (*s != 0) {
+              char c = *s++;
+              print_char(c);
+            }
+          }
+          break;
+        case FORMAT_CHAR:
+          {
+            const int c = va_arg(args, const int);
+            print_char((char)c);
+          }
+          break;
+        case FORMAT_PERCENT:
+          print_char('%');
+          break;
+        }
+      }
+      break;
+    default:
+      {
+        char c = *format++;
+        print_char(c);
+      }
+      break;
+    }
+  }
+
+  va_end(args);
+}
diff --git a/printf/printf.h b/printf/printf.h
new file mode 100644
index 0000000..ad80505
--- /dev/null
+++ b/printf/printf.h
@@ -0,0 +1,47 @@
+#pragma once
+
+#if defined(__dreamcast__)
+#include "sh7091/c_serial.h"
+#else
+#include <stdio.h>
+#endif
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline void print_char(char c)
+{
+#if defined(__dreamcast__)
+  sh7091_character(c);
+#else
+  fputc(c, stderr);
+#endif
+}
+
+void print_string(const char * s, int length);
+void print_bytes(const uint8_t * s, int length);
+void print_chars(const uint16_t * s, int length);
+void print_cstring(const char * s);
+
+void _printf(const char * format, ...);
+
+#define printf(...) _printf(__VA_ARGS__)
+#define printc(c) print_char(c)
+#define prints(s) print_cstring(s)
+
+#if defined(DEBUG_PRINT)
+#define debugf(...) _printf(__VA_ARGS__)
+#define debugc(c) print_char(c)
+#define debugs(s) print_cstring(s)
+#else
+#define debugf(...)
+#define debugc(c)
+#define debugs(c)
+#endif
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/printf/unparse.c b/printf/unparse.c
new file mode 100644
index 0000000..820e18e
--- /dev/null
+++ b/printf/unparse.c
@@ -0,0 +1,194 @@
+#include <stdint.h>
+
+#include "minmax.h"
+#include "unparse.h"
+
+int digits_base10(uint32_t n)
+{
+  if (n >= 1000000000ul) return 10;
+  if (n >= 100000000ul) return 9;
+  if (n >= 10000000ul) return 8;
+  if (n >= 1000000ul) return 7;
+  if (n >= 100000ul) return 6;
+  if (n >= 10000ul) return 5;
+  if (n >= 1000ul) return 4;
+  if (n >= 100ul) return 3;
+  if (n >= 10ul) return 2;
+  return 1;
+}
+
+int unparse_base10_unsigned(char * s, uint32_t n, int len, char fill)
+{
+  int digits = 0;
+  digits += digits_base10(n);
+  len = max(digits, len);
+  int ret = len;
+
+  while (len > digits) {
+    *s++ = fill;
+    --len;
+  }
+
+  while (len > 0) {
+    const uint32_t digit = n % 10;
+    n = n / 10;
+    s[--len] = digit + 48;
+  }
+
+  return ret;
+}
+
+int unparse_base10(char * s, int32_t n, int len, char fill)
+{
+  bool negative = false;
+  int digits = 0;
+  if (n < 0) {
+    digits += 1;
+    n = -n;
+    negative = true;
+  }
+
+  digits += digits_base10(n);
+  len = max(digits, len);
+  int ret = len;
+
+  while (len > digits) {
+    *s++ = fill;
+    --len;
+  }
+
+  if (negative) {
+    *s++ = '-';
+    len--;
+  }
+
+  while (len > 0) {
+    const uint32_t digit = n % 10;
+    n = n / 10;
+    s[--len] = digit + 48;
+  }
+
+  return ret;
+}
+
+int digits_base10_64(uint64_t n)
+{
+  if (n >= 10000000000000000000ull) return 20;
+  if (n >= 1000000000000000000ull) return 19;
+  if (n >= 100000000000000000ull) return 18;
+  if (n >= 10000000000000000ull) return 17;
+  if (n >= 1000000000000000ull) return 16;
+  if (n >= 100000000000000ull) return 15;
+  if (n >= 10000000000000ull) return 14;
+  if (n >= 1000000000000ull) return 13;
+  if (n >= 100000000000ull) return 12;
+  if (n >= 10000000000ull) return 11;
+  if (n >= 1000000000ull) return 10;
+  if (n >= 100000000ull) return 9;
+  if (n >= 10000000ull) return 8;
+  if (n >= 1000000ull) return 7;
+  if (n >= 100000ull) return 6;
+  if (n >= 10000ull) return 5;
+  if (n >= 1000ull) return 4;
+  if (n >= 100ull) return 3;
+  if (n >= 10ull) return 2;
+  return 1;
+}
+
+int unparse_base10_64(char * s, int64_t n, int len, char fill)
+{
+  bool negative = false;
+  int digits = 0;
+  if (n < 0) {
+    digits += 1;
+    n = -n;
+    negative = true;
+  }
+
+  digits += digits_base10_64(n);
+  len = max(digits, len);
+  int ret = len;
+
+  while (len > digits) {
+    *s++ = fill;
+    --len;
+  }
+
+  if (negative) {
+    *s++ = '-';
+    len--;
+  }
+
+  while (len > 0) {
+    const uint32_t digit = n % 10;
+    n = n / 10;
+    s[--len] = digit + 48;
+  }
+
+  return ret;
+}
+
+static int digits_base16(uint32_t n)
+{
+  if (n <= 0xf) return 1;
+  if (n <= 0xff) return 2;
+  if (n <= 0xfff) return 3;
+  if (n <= 0xffff) return 4;
+  if (n <= 0xfffff) return 5;
+  if (n <= 0xffffff) return 6;
+  if (n <= 0xfffffff) return 7;
+  return 8;
+}
+
+int unparse_base16(char * s, uint32_t n, int len, char fill)
+{
+  int digits = digits_base16(n);
+  len = max(digits, len);
+  int ret = len;
+
+  while (len > digits) {
+    *s++ = fill;
+    --len;
+  }
+
+  while (len > 0) {
+    uint32_t nib = n & 0xf;
+    n = n >> 4;
+    if (nib > 9) {
+      nib += (97 - 10);
+    } else {
+      nib += (48 - 0);
+    }
+
+    s[--len] = nib;
+  }
+
+  return ret;
+}
+
+#ifdef UNPARSE_TEST
+#include <stdio.h>
+
+int main()
+{
+  char s[1024];
+
+  {
+    int n = 124;
+
+    int offset = unparse_base10(s, n, 6, ' ');
+    s[offset] = 0;
+
+    printf("`%s`\n", s);
+  }
+
+  {
+    int n = 0x5678;
+
+    int offset = unparse_base16(s, n, 7, '0');
+    s[offset] = 0;
+
+    printf("`%s`\n", s);
+  }
+}
+#endif
diff --git a/printf/unparse.h b/printf/unparse.h
new file mode 100644
index 0000000..7232354
--- /dev/null
+++ b/printf/unparse.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stdint.h>
+#include "compat.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int unparse_base10_unsigned(char * s, uint32_t n, int len, char fill);
+int unparse_base10(char * s, int32_t n, int len, char fill);
+int unparse_base10_64(char * s, int64_t n, int len, char fill);
+int unparse_base16(char * s, uint32_t n, int len, char fill);
+
+int digits_base_64(uint64_t n);
+int digits_base10_64(uint64_t n);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/sh7091/c_serial.cpp b/sh7091/c_serial.cpp
new file mode 100644
index 0000000..d832594
--- /dev/null
+++ b/sh7091/c_serial.cpp
@@ -0,0 +1,15 @@
+#include "sh7091.hpp"
+#include "sh7091_bits.hpp"
+
+#include "c_serial.h"
+
+void sh7091_character(const char c)
+{
+  using namespace scif;
+  // wait for transmit fifo to become partially empty
+  while ((sh7091.SCIF.SCFSR2 & scfsr2::tdfe::bit_mask) == 0);
+
+  sh7091.SCIF.SCFSR2 &= ~scfsr2::tdfe::bit_mask;
+
+  sh7091.SCIF.SCFTDR2 = static_cast<uint8_t>(c);
+}
diff --git a/sh7091/c_serial.h b/sh7091/c_serial.h
new file mode 100644
index 0000000..733d618
--- /dev/null
+++ b/sh7091/c_serial.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void sh7091_character(const char c);
+
+#ifdef __cplusplus
+}
+#endif