diff --git a/Makefile b/Makefile
index 09a7fdd6e..c3f12af06 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ vendor: ## update git submodules
 	git submodule update --init
 
 res: ## update resources
-	./tools/res_collect.py
+	./tools/res_collect
 
 build: build_stmhal build_unix build_cross ## build stmhal, unix and mpy-cross micropython ports
 
diff --git a/docs/bootloader.md b/docs/bootloader.md
index 3c1657760..4bb3965f7 100644
--- a/docs/bootloader.md
+++ b/docs/bootloader.md
@@ -1,15 +1,26 @@
 #TREZOR Core Bootloader
 
-Bootloader code is split into two stages. See [Memory Layout](memory.md) for more info about in which sectors the code is stored.
+Bootloader is split into two stages. See [Memory Layout](memory.md) for info about in which sectors each stage is stored.
 
-First stage checks the integrity and signatures of second stage and runs it if everything is OK.
-However, if first stage bootloader finds a valid second stage bootloader on the SD card (in raw format, no filesystem), it will replace the internal second stage, allowing an upgrade of the second stage.
+First stage is stored in write-protected area, which means it is non-upgradable. Only second stage bootloader update is allowed.
 
-First stage is stored in write-protected area, which means only upgrade of the second stage bootloader is allowed.
+##First Stage Bootloader
+
+First stage checks the integrity and signatures of the second stage and runs it if everything is OK.
+
+If first stage bootloader finds a valid second stage bootloader image on the SD card (in raw format, no filesystem),
+it will replace the internal second stage, allowing a second stage update via SD card.
+
+##Second Stage Bootloader
+
+Second stage checks the integrity and signatures of the firmware and runs it if everything is OK.
+
+If second stage bootloader detects a pressed finger on the display or there is no firmware loaded in the device,
+it will start in a firmware update mode, allowing a firmware update via USB.
 
 ##Common notes
 
-* Hash function used is SHA-256 and signature system is Ed25519 (allows combining signatures by multiple keys into one).
+* Hash function used below is SHA-256 and signature system is Ed25519 (allows combining signatures by multiple keys into one).
 * All multibyte integer values are little endian.
 
 ##Bootloader Format
@@ -19,6 +30,8 @@ TREZOR Core (second stage) bootloader consists of 2 parts:
 1. bootloader header
 2. bootloader code
 
+There is a tool called [check_bootloader](../tools/check_bootloader) which parses and checks validity of the bootloader including its header.
+
 ###Bootloader Header
 
 Total length of bootloader header is 256 bytes.
@@ -26,16 +39,16 @@ Total length of bootloader header is 256 bytes.
 | offset | length | name | description |
 |-------:|-------:|------|-------------|
 | 0x0000 | 4      | magic | firmware magic `TRZB` |
-| 0x0004 | 4      | hlen | length of the bootloader header |
+| 0x0004 | 4      | hdrlen | length of the bootloader header |
 | 0x0008 | 4      | expiry | valid until timestamp (0=infinity) |
-| 0x000C | 4      | codelen | length of the bootloader code |
+| 0x000C | 4      | codelen | length of the bootloader code (without the header) |
 | 0x0010 | 1      | vmajor | version (major) |
 | 0x0011 | 1      | vminor | version (minor) |
 | 0x0012 | 1      | vpatch | version (patch) |
 | 0x0013 | 1      | vbuild | version (build) |
-| 0x0014 | 1      | slsigidx | SatoshiLabs signature indexes (bitmap) |
-| 0x0015 | 64     | slsig | SatoshiLabs signature |
-| 0x0079 | 135    | reserved | not used yet |
+| 0x0014 | 1      | sigidx | SatoshiLabs signature indexes (bitmap) |
+| 0x0015 | 64     | sig | SatoshiLabs signature |
+| 0x0055 | 171    | reserved | not used yet (zeroed) |
 
 ##Firmware Format
 
@@ -45,6 +58,8 @@ TREZOR Core firmware consists of 3 parts:
 2. firmware header
 3. firmware code
 
+There is a tool called [check_firmware](../tools/check_firmware) which parses and checks validity of the firmware including the both headers.
+
 ###Vendor Header
 
 Total length of vendor header is 82 + 32 * (number of pubkeys) + (length of vendor string) + (length of vendor image) bytes rounded up to the closest multiply of 256 bytes.
@@ -52,19 +67,19 @@ Total length of vendor header is 82 + 32 * (number of pubkeys) + (length of vend
 | offset | length | name | description |
 |-------:|-------:|------|-------------|
 | 0x0000 | 4      | magic | firmware magic `TRZV` |
-| 0x0004 | 4      | hlen | length of the vendor header |
+| 0x0004 | 4      | hdrlen | length of the vendor header |
 | 0x0008 | 4      | expiry | valid until timestamp (0=infinity) |
 | 0x000C | 1      | vsig_m | number of signatures needed to run the firmware from this vendor |
 | 0x000D | 1      | vsig_n | number of pubkeys vendor wants to use for signing |
-| 0x000E | 2      | reserved | not used yet |
+| 0x000E | 2      | reserved | not used yet (zeroed) |
 | 0x0010 | 32     | vpub1 | vendor pubkey 1 |
 | ...    | ...    | ... | ... |
 | ?      | 32     | vpubn | vendor pubkey n |
 | ?      | 1      | vstr_len | vendor string length |
 | ?      | ?      | vstr | vendor string |
 | ?      | ?      | vimg | vendor image (in [TOIf format](toif.md)) |
-| ?      | 1      | slsigidx | SatoshiLabs signature indexes (bitmap) |
-| ?      | 64     | slsig | SatoshiLabs signature |
+| ?      | 1      | sigidx | SatoshiLabs signature indexes (bitmap) |
+| ?      | 64     | sig | SatoshiLabs signature |
 
 ###Firmware Header
 
@@ -73,16 +88,16 @@ Total length of firmware header is 256 bytes.
 | offset | length | name | description |
 |-------:|-------:|------|-------------|
 | 0x0000 | 4      | magic | firmware magic `TRZF` |
-| 0x0004 | 4      | hlen | length of the firmware header |
+| 0x0004 | 4      | hdrlen | length of the firmware header |
 | 0x0008 | 4      | expiry | valid until timestamp (0=infinity) |
-| 0x000C | 4      | codelen | length of the firmware code |
+| 0x000C | 4      | codelen | length of the firmware code (without the header) |
 | 0x0010 | 1      | vmajor | version (major) |
 | 0x0011 | 1      | vminor | version (minor) |
 | 0x0012 | 1      | vpatch | version (patch) |
 | 0x0013 | 1      | vbuild | version (build) |
-| 0x0014 | 1      | vndsigidx | vendor signature indexes (bitmap) |
-| 0x0015 | 64     | vndsig | vendor signature |
-| 0x0079 | 135    | reserved | not used yet |
+| 0x0014 | 1      | sigidx | vendor signature indexes (bitmap) |
+| 0x0015 | 64     | sig | vendor signature |
+| 0x0055 | 171    | reserved | not used yet (zeroed) |
 
 ##Various ideas
 
diff --git a/docs/memory.md b/docs/memory.md
index 5df2dd437..c8673e7c8 100644
--- a/docs/memory.md
+++ b/docs/memory.md
@@ -4,18 +4,18 @@
 
 | sector    | range                   |  size   | function
 |-----------|-------------------------|--------:|----------------------
-| Sector  0 | 0x08000000 - 0x08003FFF |  16 KiB | bootloader 1st stage
-| Sector  1 | 0x08004000 - 0x08007FFF |  16 KiB | storage area
+| Sector  0 | 0x08000000 - 0x08003FFF |  16 KiB | bootloader 1st stage (write-protected)
+| Sector  1 | 0x08004000 - 0x08007FFF |  16 KiB | bootloader 1st stage (write-protected)
 | Sector  2 | 0x08008000 - 0x0800BFFF |  16 KiB | storage area
 | Sector  3 | 0x0800C000 - 0x0800FFFF |  16 KiB | storage area
 | Sector  4 | 0x08010000 - 0x0801FFFF |  64 KiB | bootloader 2nd stage
-| Sector  5 | 0x08020000 - 0x0803FFFF | 128 KiB | application code
-| Sector  6 | 0x08040000 - 0x0805FFFF | 128 KiB | application code
-| Sector  7 | 0x08060000 - 0x0807FFFF | 128 KiB | application code
-| Sector  8 | 0x08080000 - 0x0809FFFF | 128 KiB | application code
-| Sector  9 | 0x080A0000 - 0x080BFFFF | 128 KiB | application code
-| Sector 10 | 0x080C0000 - 0x080DFFFF | 128 KiB | application code
-| Sector 11 | 0x080E0000 - 0x080FFFFF | 128 KiB | application code
+| Sector  5 | 0x08020000 - 0x0803FFFF | 128 KiB | firmware
+| Sector  6 | 0x08040000 - 0x0805FFFF | 128 KiB | firmware
+| Sector  7 | 0x08060000 - 0x0807FFFF | 128 KiB | firmware
+| Sector  8 | 0x08080000 - 0x0809FFFF | 128 KiB | firmware
+| Sector  9 | 0x080A0000 - 0x080BFFFF | 128 KiB | firmware
+| Sector 10 | 0x080C0000 - 0x080DFFFF | 128 KiB | firmware
+| Sector 11 | 0x080E0000 - 0x080FFFFF | 128 KiB | firmware
 
 ##RAM
 
diff --git a/micropython/stmhal/Makefile.bootloader b/micropython/stmhal/Makefile.bootloader
index 708818d30..7d1a7689c 100644
--- a/micropython/stmhal/Makefile.bootloader
+++ b/micropython/stmhal/Makefile.bootloader
@@ -80,6 +80,7 @@ SRC_LIB = $(addprefix lib/,\
 	)
 
 SRC_C = \
+	bootloader/basic.c \
 	bootloader/bootloader.c \
 	bootloader/crypto.c \
 	bootloader/ui.c \
diff --git a/micropython/stmhal/bootloader/basic.c b/micropython/stmhal/bootloader/basic.c
new file mode 100644
index 000000000..81625ffad
--- /dev/null
+++ b/micropython/stmhal/bootloader/basic.c
@@ -0,0 +1,26 @@
+#include STM32_HAL_H
+
+// ### from main.c
+
+void __attribute__((noreturn)) __fatal_error(const char *msg) {
+    for (volatile uint32_t delay = 0; delay < 10000000; delay++) {
+    }
+    // TODO: printf("FATAL ERROR: %s\n", msg);
+    for (;;) {
+        __WFI();
+    }
+}
+
+void nlr_jump_fail(void *val) {
+    __fatal_error("FATAL: uncaught exception");
+}
+
+// ### from stm32_it.c
+
+void SysTick_Handler(void) {
+    extern uint32_t uwTick;
+    uwTick += 1;
+    SysTick->CTRL;
+}
+
+// ###
diff --git a/micropython/stmhal/bootloader/bootloader.c b/micropython/stmhal/bootloader/bootloader.c
index a31f271ea..06eb23000 100644
--- a/micropython/stmhal/bootloader/bootloader.c
+++ b/micropython/stmhal/bootloader/bootloader.c
@@ -2,75 +2,10 @@
 
 #include "crypto.h"
 #include "ui.h"
-
 #include "display.h"
 
-// ### from main.c
-
-void flash_error(int n) {
-    for (int i = 0; i < n; i++) {
-        // blink(on)
-        HAL_Delay(250);
-        // blink(off)
-        HAL_Delay(250);
-    }
-}
-
-void __attribute__((noreturn)) __fatal_error(const char *msg) {
-    for (volatile uint32_t delay = 0; delay < 10000000; delay++) {
-    }
-    // TODO: printf("FATAL ERROR: %s\n", msg);
-    for (;;) {
-        __WFI();
-    }
-}
-
-void nlr_jump_fail(void *val) {
-    __fatal_error("FATAL: uncaught exception");
-}
-
 void SystemClock_Config(void);
 
-// ### from stm32_it.c
-
-/**
-  * @brief  This function handles SysTick Handler.
-  * @param  None
-  * @retval None
-  */
-void SysTick_Handler(void) {
-    // Instead of calling HAL_IncTick we do the increment here of the counter.
-    // This is purely for efficiency, since SysTick is called 1000 times per
-    // second at the highest interrupt priority.
-    // Note: we don't need uwTick to be declared volatile here because this is
-    // the only place where it can be modified, and the code is more efficient
-    // without the volatile specifier.
-    extern uint32_t uwTick;
-    uwTick += 1;
-
-    // Read the systick control regster. This has the side effect of clearing
-    // the COUNTFLAG bit, which makes the logic in sys_tick_get_microseconds
-    // work properly.
-    SysTick->CTRL;
-
-#if 0
-    // Right now we have the storage and DMA controllers to process during
-    // this interrupt and we use custom dispatch handlers.  If this needs to
-    // be generalised in the future then a dispatch table can be used as
-    // follows: ((void(*)(void))(systick_dispatch[uwTick & 0xf]))();
-
-    if (STORAGE_IDLE_TICK(uwTick)) {
-        NVIC->STIR = FLASH_IRQn;
-    }
-
-    if (DMA_IDLE_ENABLED() && DMA_IDLE_TICK(uwTick)) {
-        dma_idle_handler(uwTick);
-    }
-#endif
-}
-
-// ###
-
 int main(void) {
 
     HAL_Init();
@@ -101,7 +36,5 @@ int main(void) {
         HAL_Delay(250);
     }
 
-    __fatal_error("end");
-
     return 0;
 }
diff --git a/micropython/stmhal/bootloader/ui.c b/micropython/stmhal/bootloader/ui.c
index 2097152de..6aaa12879 100644
--- a/micropython/stmhal/bootloader/ui.c
+++ b/micropython/stmhal/bootloader/ui.c
@@ -10,7 +10,7 @@
 
 void screen_welcome(void)
 {
-    display_image(0, 0, 240, 240, toi_trezor, sizeof(toi_trezor));
+    display_icon(0, 0, 240, 240, toi_trezor, sizeof(toi_trezor), ui_WHITE, ui_BLACK);
     display_text(0, 240, "bootloader", 10, FONT_MONO, ui_WHITE, ui_BLACK);
 }
 
diff --git a/tools/build_pb.sh b/tools/build_protobuf
similarity index 100%
rename from tools/build_pb.sh
rename to tools/build_protobuf
diff --git a/tools/check_bootloader b/tools/check_bootloader
new file mode 100755
index 000000000..619a35735
--- /dev/null
+++ b/tools/check_bootloader
@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+import sys
+import struct
+
+# bootloader header specification: https://github.com/trezor/trezor-core/blob/master/docs/bootloader.md#bootloader-header
+
+def check_bootloader(filename):
+    data = open(filename, 'rb').read()
+    hdr = struct.unpack('<4sIIIBBBBB64s171s', data[:256])
+    code = data[256:]
+    magic, hdrlen, expiry, codelen, vmajor, vminor, vpatch, vbuild, sigidx, sig, reserved = hdr
+    sigidx = tuple([ i + 1 for i in range(8) if sigidx & (1 << i) ])
+    print('magic    :', magic)
+    assert magic == b'TRZB'
+    print('hdrlen   :', hdrlen)
+    assert hdrlen == 256
+    print('expiry   :', expiry)
+    print('codelen  :', codelen)
+    print('vmajor   :', vmajor)
+    print('vminor   :', vminor)
+    print('vpatch   :', vpatch)
+    print('vbuild   :', vbuild)
+    print('sigidx   :', sigidx)
+    print('sig      :', sig)
+    assert reserved == 171 * b'\x00'
+    assert codelen == 64*1024
+    assert codelen == len(code)
+
+
+def main():
+    if len(sys.argv) < 2:
+        print('Usage: check_bootloader bootloader.bin')
+        return 1
+    fn = sys.argv[1]
+    check_bootloader(fn)
+
+
+main()
diff --git a/tools/check_firmware b/tools/check_firmware
new file mode 100755
index 000000000..7412a1238
--- /dev/null
+++ b/tools/check_firmware
@@ -0,0 +1,17 @@
+#!/usr/bin/env python3
+import sys
+
+
+def process_firmware(filename):
+    data = open(filename, 'rb').read()
+
+
+def main():
+    if len(sys.argv) < 2:
+        print('Usage: check_firmware firmware.bin')
+        return 1
+    fn = sys.argv[1]
+    process_firmware(fn)
+
+
+main()
diff --git a/tools/coins-gen.py b/tools/coins_gen
similarity index 100%
rename from tools/coins-gen.py
rename to tools/coins_gen
diff --git a/tools/res_collect.py b/tools/res_collect
similarity index 100%
rename from tools/res_collect.py
rename to tools/res_collect
diff --git a/tools/toi2png b/tools/toi2png
index c36fe5c7e..98078d454 100755
--- a/tools/toi2png
+++ b/tools/toi2png
@@ -73,7 +73,7 @@ def process_image(ifn):
 
 def main():
     if len(sys.argv) < 2:
-        print('Usage toi2png image.toi[fg]')
+        print('Usage: toi2png image.toi[fg]')
         return 1
 
     ifn = sys.argv[1]