modtrezorui: introduce display_printf, use where possible

Makefile.boardloader

@@ -77,6 +77,7 @@ OBJ_TREZORHAL += $(addprefix $(BUILD_FW)/, \
 	trezorhal/common.o \
 	trezorhal/image.o \
 	trezorhal/flash.o \
+	trezorhal/mini_printf.o \
 	trezorhal/sdcard.o \
 	trezorhal/stm32_it.o \
 	trezorhal/stm32_system.o \

Makefile.bootloader

@@ -86,6 +86,7 @@ OBJ_TREZORHAL += $(addprefix $(BUILD_FW)/, \
 	trezorhal/common.o \
 	trezorhal/image.o \
 	trezorhal/flash.o \
+	trezorhal/mini_printf.o \
 	trezorhal/stm32_it.o \
 	trezorhal/stm32_system.o \
 	trezorhal/touch.o \

Makefile.firmware

@@ -317,6 +317,7 @@ OBJ_FIRMWARE += $(addprefix $(BUILD_FW)/, \
 OBJ_TREZORHAL += $(addprefix $(BUILD_FW)/, \
 	trezorhal/common.o \
 	trezorhal/flash.o \
+	trezorhal/mini_printf.o \
 	trezorhal/rng.o \
 	trezorhal/sdcard.o \
 	trezorhal/stm32_it.o \

micropython/boardloader/main.c

@@ -18,20 +18,20 @@ void pendsv_isr_handler(void) {
 
 bool check_sdcard(void)
 {
-    DPRINTLN("checking for SD card");
+    display_printf("checking for SD card\n");
 
     if (!sdcard_is_present()) {
-        DPRINTLN("no SD card found");
+        display_printf("no SD card found\n");
         return false;
     }
 
-    DPRINTLN("SD card found");
+    display_printf("SD card found\n");
 
     sdcard_power_on();
 
     uint64_t cap = sdcard_get_capacity_in_bytes();
     if (cap < 1024 * 1024) {
-        DPRINTLN("SD card too small");
+        display_printf("SD card too small\n");
         sdcard_power_off();
         return false;
     }
@@ -43,18 +43,17 @@ bool check_sdcard(void)
     sdcard_power_off();
 
     if (image_parse_header((const uint8_t *)buf, IMAGE_MAGIC, IMAGE_MAXSIZE, NULL)) {
-        DPRINTLN("SD card header is valid");
+        display_printf("SD card header is valid\n");
         return true;
     } else {
-        DPRINTLN("SD card header is invalid");
+        display_printf("SD card header is invalid\n");
         return false;
     }
 }
 
 bool copy_sdcard(void)
 {
-
+    display_printf("erasing flash ");
-    DPRINT("erasing flash ");
 
     // erase flash (except boardloader)
     HAL_FLASH_Unlock();
@@ -69,14 +68,14 @@ bool copy_sdcard(void)
         EraseInitStruct.Sector = i;
         if (HAL_FLASHEx_Erase(&EraseInitStruct, &SectorError) != HAL_OK) {
             HAL_FLASH_Lock();
-            DPRINTLN(" failed");
+            display_printf(" failed\n");
             return false;
         }
-        DPRINT(".");
+        display_printf(".");
     }
-    DPRINTLN(" done");
+    display_printf(" done\n");
 
-    DPRINTLN("copying new bootloader from SD card");
+    display_printf("copying new bootloader from SD card\n");
 
     sdcard_power_on();
 
@@ -86,7 +85,7 @@ bool copy_sdcard(void)
 
     image_header hdr;
     if (!image_parse_header((const uint8_t *)buf, IMAGE_MAGIC, IMAGE_MAXSIZE, &hdr)) {
-        DPRINTLN("invalid header");
+        display_printf("invalid header\n");
         sdcard_power_off();
         HAL_FLASH_Lock();
         return false;
@@ -96,7 +95,7 @@ bool copy_sdcard(void)
         sdcard_read_blocks((uint8_t *)buf, i, 1);
         for (int j = 0; j < SDCARD_BLOCK_SIZE / sizeof(uint32_t); j++) {
             if (HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, BOOTLOADER_START + i * SDCARD_BLOCK_SIZE + j * sizeof(uint32_t), buf[j]) != HAL_OK) {
-                DPRINTLN("copy failed");
+                display_printf("copy failed\n");
                 sdcard_power_off();
                 HAL_FLASH_Lock();
                 return false;
@@ -107,36 +106,36 @@ bool copy_sdcard(void)
     sdcard_power_off();
     HAL_FLASH_Lock();
 
-    DPRINTLN("done");
+    display_printf("done\n");
 
     return true;
 }
 
 void check_and_jump(void)
 {
-    DPRINTLN("checking bootloader");
+    display_printf("checking bootloader\n");
 
     image_header hdr;
 
     if (image_parse_header((const uint8_t *)BOOTLOADER_START, IMAGE_MAGIC, IMAGE_MAXSIZE, &hdr)) {
-        DPRINTLN("valid bootloader header");
+        display_printf("valid bootloader header\n");
     } else {
-        DPRINTLN("invalid bootloader header");
+        display_printf("invalid bootloader header\n");
         return;
     }
 
     if (image_check_signature((const uint8_t *)BOOTLOADER_START, &hdr, NULL)) {
-        DPRINTLN("valid bootloader signature");
+        display_printf("valid bootloader signature\n");
 
         // TODO: remove debug wait
-        DPRINTLN("waiting 1 second");
+        display_printf("waiting 1 second\n");
         HAL_Delay(1000);
         // end
-        DPRINTLN("JUMP!");
+        display_printf("JUMP!\n");
         jump_to(BOOTLOADER_START + HEADER_SIZE);
 
     } else {
-        DPRINTLN("invalid bootloader signature");
+        display_printf("invalid bootloader signature\n");
     }
 }
 
@@ -160,9 +159,9 @@ int main(void)
     display_clear();
     display_backlight(255);
 
-    DPRINTLN("TREZOR Boardloader " VERSION_STR);
+    display_printf("TREZOR Boardloader %d.%d.%d.%d\n", VERSION_MAJOR, VERSION_MINOR, VERSION_PATCH, VERSION_BUILD);
-    DPRINTLN("==================");
+    display_printf("==================\n");
-    DPRINTLN("starting boardloader");
+    display_printf("starting boardloader\n");
 
     if (check_sdcard()) {
         if (!copy_sdcard()) {

micropython/boardloader/version.h

@@ -2,8 +2,3 @@
 #define VERSION_MINOR 1
 #define VERSION_PATCH 0
 #define VERSION_BUILD 0
-
-#define STR_HELPER(X) #X
-#define STRINGIZE(X) STR_HELPER(X)
-
-#define VERSION_STR STRINGIZE(VERSION_MAJOR) "." STRINGIZE(VERSION_MINOR) "." STRINGIZE(VERSION_PATCH) "." STRINGIZE(VERSION_BUILD)

micropython/bootloader/main.c

@@ -11,6 +11,7 @@
 #include "touch.h"
 #include "usb.h"
 #include "version.h"
+#include "mini_printf.h"
 
 #include "messages.h"
 #include "protobuf.h"
@@ -36,55 +37,56 @@ void display_vendor(const uint8_t *vimg, const char *vstr, uint32_t vstr_len, ui
     uint32_t datalen = *(uint32_t *)(vimg + 8);
     display_image(60, 32, w, h, vimg + 12, datalen);
     display_text_center(120, 192, vstr, vstr_len, FONT_BOLD, COLOR_WHITE, COLOR_BLACK);
-    char ver_str[] = "0.0.0.0";
+    char ver_str[32];
-    // TODO: fixme - the following does not work for values >= 10
+    mini_snprintf(ver_str, sizeof(ver_str), "%d.%d.%d.%d",
-    ver_str[0] += fw_version & 0xFF;
+        fw_version & 0xFF,
-    ver_str[2] += (fw_version >> 8) & 0xFF;
+        (fw_version >> 8) & 0xFF,
-    ver_str[4] += (fw_version >> 16) & 0xFF;
+        (fw_version >> 16) & 0xFF,
-    ver_str[6] += (fw_version >> 24) & 0xFF;
+        (fw_version >> 24) & 0xFF
+    );
     display_text_center(120, 215, ver_str, -1, FONT_BOLD, COLOR_GRAY64, COLOR_BLACK);
     display_refresh();
 }
 
 void check_and_jump(void)
 {
-    DPRINTLN("checking vendor header");
+    display_printf("checking vendor header\n");
 
     vendor_header vhdr;
     if (vendor_parse_header((const uint8_t *)FIRMWARE_START, &vhdr)) {
-        DPRINTLN("valid vendor header");
+        display_printf("valid vendor header\n");
     } else {
-        DPRINTLN("invalid vendor header");
+        display_printf("invalid vendor header\n");
         return;
     }
 
     if (vendor_check_signature((const uint8_t *)FIRMWARE_START, &vhdr)) {
-        DPRINTLN("valid vendor header signature");
+        display_printf("valid vendor header signature\n");
     } else {
-        DPRINTLN("invalid vendor header signature");
+        display_printf("invalid vendor header signature\n");
         return;
     }
 
-    DPRINTLN("checking firmware header");
+    display_printf("checking firmware header\n");
 
     image_header hdr;
     if (image_parse_header((const uint8_t *)(FIRMWARE_START + vhdr.hdrlen), IMAGE_MAGIC, IMAGE_MAXSIZE, &hdr)) {
-        DPRINTLN("valid firmware header");
+        display_printf("valid firmware header\n");
     } else {
-        DPRINTLN("invalid firmware header");
+        display_printf("invalid firmware header\n");
         return;
     }
 
     if (image_check_signature((const uint8_t *)(FIRMWARE_START + vhdr.hdrlen), &hdr, &vhdr)) {
-        DPRINTLN("valid firmware signature");
+        display_printf("valid firmware signature\n");
 
         display_vendor(vhdr.vimg, (const char *)vhdr.vstr, vhdr.vstr_len, hdr.version);
         HAL_Delay(1000); // TODO: remove?
-        DPRINTLN("JUMP!");
+        display_printf("JUMP!\n");
         jump_to(FIRMWARE_START + vhdr.hdrlen + HEADER_SIZE);
 
     } else {
-        DPRINTLN("invalid firmware signature");
+        display_printf("invalid firmware signature\n");
     }
 }
 
@@ -175,7 +177,7 @@ uint32_t process_upload_message(uint32_t msg_size, const uint8_t *initbuf, uint3
         process_upload_chunk(buf, 63);
         remains -= USB_PACKET_SIZE;
     }
-    DPRINTLN("done");
+    display_printf("done\n");
     return 0; // should return >0 if more data required
 }
 
@@ -205,19 +207,19 @@ void mainloop(void)
         }
         switch (msg_id) {
             case 0: // Initialize
-                DPRINTLN("received Initialize");
+                display_printf("received Initialize\n");
                 send_msg_Features(USB_IFACE_NUM, false);
                 break;
             case 1: // Ping
-                DPRINTLN("received Ping");
+                display_printf("received Ping\n");
                 send_msg_Success(USB_IFACE_NUM);
                 break;
             case 6: // FirmwareErase
-                DPRINTLN("received FirmwareErase");
+                display_printf("received FirmwareErase\n");
                 send_msg_FirmwareRequest(USB_IFACE_NUM, 0, UPLOAD_CHUNK_SIZE);
                 break;
             case 7: // FirmwareUpload
-                DPRINTLN("received FirmwareUpload");
+                display_printf("received FirmwareUpload\n");
                 uint32_t req_offset = process_upload_message(msg_size, buf + PB_HEADER_LEN, USB_PACKET_SIZE - PB_HEADER_LEN);
                 if (req_offset > 0) {
                     send_msg_FirmwareRequest(USB_IFACE_NUM, req_offset, UPLOAD_CHUNK_SIZE);
@@ -226,7 +228,7 @@ void mainloop(void)
                 }
                 break;
             default:
-                DPRINTLN("received unknown message");
+                display_printf("received unknown message\n");
                 send_msg_Failure(USB_IFACE_NUM);
                 break;
         }
@@ -248,9 +250,9 @@ int main(void)
     display_clear();
     display_backlight(255);
 
-    DPRINTLN("TREZOR Bootloader " VERSION_STR);
+    display_printf("TREZOR Bootloader %d.%d.%d.%d\n", VERSION_MAJOR, VERSION_MINOR, VERSION_PATCH, VERSION_BUILD);
-    DPRINTLN("=================");
+    display_printf("=================\n");
-    DPRINTLN("starting bootloader");
+    display_printf("starting bootloader\n");
 
     if (touch_read() != 0) {
         mainloop();

micropython/bootloader/version.h

@@ -2,12 +2,3 @@
 #define VERSION_MINOR 1
 #define VERSION_PATCH 0
 #define VERSION_BUILD 0
-
-#define VERSION_MAJOR_CHAR "\x00"
-#define VERSION_MINOR_CHAR "\x01"
-#define VERSION_PATCH_CHAR "\x00"
-
-#define STR_HELPER(X) #X
-#define STRINGIZE(X) STR_HELPER(X)
-
-#define VERSION_STR STRINGIZE(VERSION_MAJOR) "." STRINGIZE(VERSION_MINOR) "." STRINGIZE(VERSION_PATCH) "." STRINGIZE(VERSION_BUILD)

micropython/extmod/modtrezorui/display.c

@@ -20,7 +20,9 @@
 #include "trezor-qrenc/qr_encode.h"
 
 #include "display.h"
+
 #include <string.h>
+#include <stdarg.h>
 
 static int DISPLAY_BACKLIGHT = 0;
 static int DISPLAY_ORIENTATION = 0;
@@ -29,6 +31,7 @@ static int DISPLAY_OFFSET[2] = {0, 0};
 #if defined TREZOR_STM32
 #include "display-stm32.h"
 #elif defined TREZOR_UNIX
+#include <stdio.h>
 #include "display-unix.h"
 #else
 #error Unsupported TREZOR port. Only STM32 and UNIX ports are supported.
@@ -240,11 +243,21 @@ static const uint8_t *get_glyph(uint8_t font, uint8_t c)
     return 0;
 }
 
+#ifndef TREZOR_PRINT_DISABLE
+
 #define DISPLAY_PRINT_COLS (DISPLAY_RESX / 6)
 #define DISPLAY_PRINT_ROWS (DISPLAY_RESY / 8)
 static char display_print_buf[DISPLAY_PRINT_ROWS][DISPLAY_PRINT_COLS];
+static uint16_t display_print_fgcolor = COLOR_WHITE, display_print_bgcolor = COLOR_BLACK;
 
-// display text using bitmap font - print to internal buffer
+// set colors for display_print function
+void display_print_color(uint16_t fgcolor, uint16_t bgcolor)
+{
+    display_print_fgcolor = fgcolor;
+    display_print_bgcolor = bgcolor;
+}
+
+// display text using bitmap font
 void display_print(const char *text, int textlen)
 {
     static uint8_t row = 0, col = 0;
@@ -254,7 +267,9 @@ void display_print(const char *text, int textlen)
         textlen = strlen(text);
     }
 
+    // print characters to internal buffer (display_print_buf)
     for (int i = 0; i < textlen; i++) {
+
         switch (text[i]) {
             case '\r':
                 break;
@@ -267,10 +282,12 @@ void display_print(const char *text, int textlen)
                 col++;
                 break;
         }
+
         if (col >= DISPLAY_PRINT_COLS) {
             col = 0;
             row++;
         }
+
         if (row >= DISPLAY_PRINT_ROWS) {
             for (int j = 0; j < DISPLAY_PRINT_ROWS - 1; j++) {
                 memcpy(display_print_buf[j], display_print_buf[j + 1], DISPLAY_PRINT_COLS);
@@ -278,11 +295,10 @@ void display_print(const char *text, int textlen)
             memset(display_print_buf[DISPLAY_PRINT_ROWS - 1], 0x00, DISPLAY_PRINT_COLS);
             row = DISPLAY_PRINT_ROWS - 1;
         }
-    }
+
     }
 
-// display text using bitmap font - send internal buffer to display
+    // render buffer to display
-void display_print_out(uint16_t fgcolor, uint16_t bgcolor) {
     display_set_window(0, 0, DISPLAY_RESX - 1, DISPLAY_RESY - 1);
     for (int i = 0; i < DISPLAY_RESX * DISPLAY_RESY; i++) {
         int x = (i % DISPLAY_RESX);
@@ -294,15 +310,41 @@ void display_print_out(uint16_t fgcolor, uint16_t bgcolor) {
         if (c < ' ') c = ' ';
         const uint8_t *g = Font_Bitmap + (5 * (c - ' '));
         if (k < 5 && (g[k] & (1 << j))) {
-            DATA(fgcolor >> 8);
+            DATA(display_print_fgcolor >> 8);
-            DATA(fgcolor & 0xFF);
+            DATA(display_print_fgcolor & 0xFF);
         } else {
-            DATA(bgcolor >> 8);
+            DATA(display_print_bgcolor >> 8);
-            DATA(bgcolor & 0xFF);
+            DATA(display_print_bgcolor & 0xFF);
         }
     }
+    display_refresh();
 }
 
+#ifndef TREZOR_UNIX
+extern int mini_vsnprintf(char* buffer, unsigned int buffer_len, const char *fmt, va_list va);
+#endif
+
+// variadic display_print
+void display_printf(const char *fmt, ...)
+{
+    if (!strchr(fmt, '%')) {
+        display_print(fmt, strlen(fmt));
+    } else {
+        va_list va;
+        va_start(va, fmt);
+        char buf[256];
+#ifndef TREZOR_UNIX
+        int len = mini_vsnprintf(buf, sizeof(buf), fmt, va);
+#else
+        int len = vsnprintf(buf, sizeof(buf), fmt, va);
+#endif
+        display_print(buf, len);
+        va_end(va);
+    }
+}
+
+#endif // TREZOR_PRINT_DISABLE
+
 // first two bytes are width and height of the glyph
 // third, fourth and fifth bytes are advance, bearingX and bearingY of the horizontal metrics of the glyph
 // rest is packed 4-bit glyph data

micropython/extmod/modtrezorui/display.h

@@ -51,8 +51,11 @@ void display_bar_radius(int x, int y, int w, int h, uint16_t c, uint16_t b, uint
 void display_image(int x, int y, int w, int h, const void *data, int datalen);
 void display_icon(int x, int y, int w, int h, const void *data, int datalen, uint16_t fgcolor, uint16_t bgcolor);
 
+#ifndef TREZOR_PRINT_DISABLE
+void display_print_color(uint16_t fgcolor, uint16_t bgcolor);
 void display_print(const char *text, int textlen);
-void display_print_out(uint16_t fgcolor, uint16_t bgcolor);
+void display_printf(const char *fmt, ...);
+#endif
 
 void display_text(int x, int y, const char *text, int textlen, uint8_t font, uint16_t fgcolor, uint16_t bgcolor);
 void display_text_center(int x, int y, const char *text, int textlen, uint8_t font, uint16_t fgcolor, uint16_t bgcolor);

micropython/extmod/modtrezorui/modtrezorui-display.h

@@ -126,22 +126,19 @@ STATIC mp_obj_t mod_TrezorUi_Display_icon(size_t n_args, const mp_obj_t *args) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_TrezorUi_Display_icon_obj, 6, 6, mod_TrezorUi_Display_icon);
 
-/// def trezor.ui.display.print(text: str, fgcolor: int, bgcolor: int) -> None:
+/// def trezor.ui.display.print(text: str) -> None:
 ///     '''
 ///     Renders text using 5x8 bitmap font (using special text mode)
 ///     '''
-STATIC mp_obj_t mod_TrezorUi_Display_print(size_t n_args, const mp_obj_t *args) {
+STATIC mp_obj_t mod_TrezorUi_Display_print(mp_obj_t self, mp_obj_t text) {
     mp_buffer_info_t buf;
-    mp_get_buffer_raise(args[1], &buf, MP_BUFFER_READ);
+    mp_get_buffer_raise(text, &buf, MP_BUFFER_READ);
-    mp_int_t fgcolor = mp_obj_get_int(args[2]);
-    mp_int_t bgcolor = mp_obj_get_int(args[3]);
     if (buf.len > 0) {
         display_print(buf.buf, buf.len);
     }
-    display_print_out(fgcolor, bgcolor);
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_TrezorUi_Display_print_obj, 4, 4, mod_TrezorUi_Display_print);
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_TrezorUi_Display_print_obj, mod_TrezorUi_Display_print);
 
 /// def trezor.ui.display.text(x: int, y: int, text: str, font: int, fgcolor: int, bgcolor: int) -> None:
 ///     '''

micropython/trezorhal/common.c

@@ -4,18 +4,15 @@
 #include "display.h"
 
 void __attribute__((noreturn)) __fatal_error(const char *msg, const char *file, int line, const char *func) {
-    for (volatile uint32_t delay = 0; delay < 10000000; delay++) {
+    for (volatile uint32_t delay = 0; delay < 10000000; delay++) {}
-    }
+    display_print_color(COLOR_WHITE, COLOR_RED128);
-    display_print("\nFATAL ERROR:\n", -1);
+    display_printf("\nFATAL ERROR:\n%s\n", msg);
-    display_print(msg, -1);
     if (file) {
-        display_print("\nFile: ", -1); display_print(file, -1); (void)line;
+        display_printf("File: %s:%d\n", file, line);
     }
     if (func) {
-        display_print("\nFunc: ", -1); display_print(func, -1);
+        display_printf("Func: %s\n", func);
     }
-    display_print("\n", 1);
-    display_print_out(COLOR_WHITE, COLOR_RED128);
     for (;;) {
         display_backlight(255);
         HAL_Delay(950);
@@ -26,9 +23,7 @@ void __attribute__((noreturn)) __fatal_error(const char *msg, const char *file,
 
 #ifndef NDEBUG
 void __assert_func(const char *file, int line, const char *func, const char *expr) {
-    display_print("\nassert(", -1);
+    display_printf("\nassert(%s)\n", expr);
-    display_print(expr, -1);
-    display_print(")\n", 2);
     __fatal_error("Assertion failed", file, line, func);
 }
 #endif

micropython/trezorhal/common.h

@@ -16,9 +16,4 @@ void __attribute__((noreturn)) nlr_jump_fail(void *val);
 
 void jump_to(uint32_t address);
 
-// common helper macros
-
-#define DPRINT(X)   do { display_print(X, -1);      display_print_out(COLOR_WHITE, COLOR_BLACK); } while(0)
-#define DPRINTLN(X) do { display_print(X "\n", -1); display_print_out(COLOR_WHITE, COLOR_BLACK); } while(0)
-
 #endif

micropython/trezorhal/mini_printf.c

@@ -0,0 +1,199 @@
+/*
+ * The Minimal snprintf() implementation
+ *
+ * Copyright (c) 2013,2014 Michal Ludvig <michal@logix.cz>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the auhor nor the names of its contributors
+ *       may be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * ----
+ *
+ * This is a minimal snprintf() implementation optimised
+ * for embedded systems with a very limited program memory.
+ * mini_snprintf() doesn't support _all_ the formatting
+ * the glibc does but on the other hand is a lot smaller.
+ * Here are some numbers from my STM32 project (.bin file size):
+ *      no snprintf():      10768 bytes
+ *      mini snprintf():    11420 bytes     (+  652 bytes)
+ *      glibc snprintf():   34860 bytes     (+24092 bytes)
+ * Wasting nearly 24kB of memory just for snprintf() on
+ * a chip with 32kB flash is crazy. Use mini_snprintf() instead.
+ *
+ */
+
+#include <string.h>
+#include <stdarg.h>
+#include "mini_printf.h"
+
+static unsigned int
+mini_strlen(const char *s)
+{
+	unsigned int len = 0;
+	while (s[len] != '\0') len++;
+	return len;
+}
+
+static unsigned int
+mini_itoa(int value, unsigned int radix, unsigned int uppercase, unsigned int unsig,
+	 char *buffer, unsigned int zero_pad)
+{
+	char	*pbuffer = buffer;
+	int	negative = 0;
+	unsigned int	i, len;
+
+	/* No support for unusual radixes. */
+	if (radix > 16)
+		return 0;
+
+	if (value < 0 && !unsig) {
+		negative = 1;
+		value = -value;
+	}
+
+	/* This builds the string back to front ... */
+	do {
+		int digit = value % radix;
+		*(pbuffer++) = (digit < 10 ? '0' + digit : (uppercase ? 'A' : 'a') + digit - 10);
+		value /= radix;
+	} while (value > 0);
+
+	for (i = (pbuffer - buffer); i < zero_pad; i++)
+		*(pbuffer++) = '0';
+
+	if (negative)
+		*(pbuffer++) = '-';
+
+	*(pbuffer) = '\0';
+
+	/* ... now we reverse it (could do it recursively but will
+	 * conserve the stack space) */
+	len = (pbuffer - buffer);
+	for (i = 0; i < len / 2; i++) {
+		char j = buffer[i];
+		buffer[i] = buffer[len-i-1];
+		buffer[len-i-1] = j;
+	}
+
+	return len;
+}
+
+int
+mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list va)
+{
+	char *pbuffer = buffer;
+	char bf[24];
+	char ch;
+
+	int _putc(char ch)
+	{
+		if ((unsigned int)((pbuffer - buffer) + 1) >= buffer_len)
+			return 0;
+		*(pbuffer++) = ch;
+		*(pbuffer) = '\0';
+		return 1;
+	}
+
+	int _puts(char *s, unsigned int len)
+	{
+		unsigned int i;
+
+		if (buffer_len - (pbuffer - buffer) - 1 < len)
+			len = buffer_len - (pbuffer - buffer) - 1;
+
+		/* Copy to buffer */
+		for (i = 0; i < len; i++)
+			*(pbuffer++) = s[i];
+		*(pbuffer) = '\0';
+
+		return len;
+	}
+
+	while ((ch=*(fmt++))) {
+		if ((unsigned int)((pbuffer - buffer) + 1) >= buffer_len)
+			break;
+		if (ch!='%')
+			_putc(ch);
+		else {
+			char zero_pad = 0;
+			char *ptr;
+			unsigned int len;
+
+			ch=*(fmt++);
+
+			/* Zero padding requested */
+			if (ch=='0') {
+				ch=*(fmt++);
+				if (ch == '\0')
+					goto end;
+				if (ch >= '0' && ch <= '9')
+					zero_pad = ch - '0';
+				ch=*(fmt++);
+			}
+
+			switch (ch) {
+				case 0:
+					goto end;
+
+				case 'u':
+				case 'd':
+					len = mini_itoa(va_arg(va, unsigned int), 10, 0, (ch=='u'), bf, zero_pad);
+					_puts(bf, len);
+					break;
+
+				case 'x':
+				case 'X':
+					len = mini_itoa(va_arg(va, unsigned int), 16, (ch=='X'), 1, bf, zero_pad);
+					_puts(bf, len);
+					break;
+
+				case 'c' :
+					_putc((char)(va_arg(va, int)));
+					break;
+
+				case 's' :
+					ptr = va_arg(va, char*);
+					_puts(ptr, mini_strlen(ptr));
+					break;
+
+				default:
+					_putc(ch);
+					break;
+			}
+		}
+	}
+end:
+	return pbuffer - buffer;
+}
+
+
+int
+mini_snprintf(char* buffer, unsigned int buffer_len, const char *fmt, ...)
+{
+	int ret;
+	va_list va;
+	va_start(va, fmt);
+	ret = mini_vsnprintf(buffer, buffer_len, fmt, va);
+	va_end(va);
+
+	return ret;
+}

micropython/trezorhal/mini_printf.h

@@ -0,0 +1,47 @@
+/*
+ * The Minimal snprintf() implementation
+ *
+ * Copyright (c) 2013 Michal Ludvig <michal@logix.cz>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the auhor nor the names of its contributors
+ *       may be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+#ifndef __MINI_PRINTF__
+#define __MINI_PRINTF__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdarg.h>
+
+int mini_vsnprintf(char* buffer, unsigned int buffer_len, const char *fmt, va_list va);
+int mini_snprintf(char* buffer, unsigned int buffer_len, const char *fmt, ...);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif