Merge branch 'master' into stable

11 files changed, 286 insertions, 112 deletions

diff --git a/xs/src/avrdude/arduino.c b/xs/src/avrdude/arduino.c
index 566f56abd..5a9cb465e 100644
--- a/xs/src/avrdude/arduino.c
+++ b/xs/src/avrdude/arduino.c
@@ -80,6 +80,49 @@ static int arduino_read_sig_bytes(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m)
   return 3;
 }
 
+static int prusa_init_external_flash(PROGRAMMER * pgm)
+{
+  // Note: send/receive as in _the firmare_ send & receives
+  const char entry_magic_send   [] = "start\n";
+  const char entry_magic_receive[] = "w25x20cl_enter\n";
+  const char entry_magic_cfm    [] = "w25x20cl_cfm\n";
+  const size_t buffer_len = 32;     // Should be large enough for the above messages
+
+  int res;
+  size_t recv_size;
+  char *buffer = alloca(buffer_len);
+
+  // 1. receive the "start" command
+  recv_size = sizeof(entry_magic_send) - 1;
+  res = serial_recv(&pgm->fd, buffer, recv_size);
+  if (res < 0) {
+    avrdude_message(MSG_INFO, "%s: prusa_init_external_flash(): MK3 printer did not boot up on time or serial communication failed\n", progname);
+    return -1;
+  } else if (strncmp(buffer, entry_magic_send, recv_size) != 0) {
+    avrdude_message(MSG_INFO, "%s: prusa_init_external_flash(): MK3 printer emitted incorrect start code: `%*s`\n", progname, recv_size, buffer);
+    return -1;
+  }
+
+  // 2. Send the external flash programmer enter command
+  if (serial_send(&pgm->fd, entry_magic_receive, sizeof(entry_magic_receive) - 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: prusa_init_external_flash(): Failed to send command to the printer\n",progname);
+    return -1;
+  }
+
+  // 3. Receive the entry confirmation command
+  recv_size = sizeof(entry_magic_cfm) - 1;
+  res = serial_recv(&pgm->fd, buffer, recv_size);
+  if (res < 0) {
+    avrdude_message(MSG_INFO, "%s: prusa_init_external_flash(): MK3 printer did not boot up on time or serial communication failed\n", progname);
+    return -1;
+  } else if (strncmp(buffer, entry_magic_cfm, recv_size) != 0) {
+    avrdude_message(MSG_INFO, "%s: prusa_init_external_flash(): MK3 printer emitted incorrect cfm code: `%*s`\n", progname, recv_size, buffer);
+    return -1;
+  }
+
+  return 0;
+}
+
 static int arduino_open(PROGRAMMER * pgm, char * port)
 {
   union pinfo pinfo;
@@ -97,11 +140,24 @@ static int arduino_open(PROGRAMMER * pgm, char * port)
   serial_set_dtr_rts(&pgm->fd, 1);
   usleep(50*1000);
 
+  // Sometimes there may be line noise generating input on the printer's USB-to-serial IC
+  // Here we try to clean its input buffer with a sequence of newlines (a minimum of 9 is needed):
+  const char cleanup_newlines[] = "\n\n\n\n\n\n\n\n\n\n";
+  if (serial_send(&pgm->fd, cleanup_newlines, sizeof(cleanup_newlines) - 1) < 0) {
+    return -1;
+  }
+
   /*
    * drain any extraneous input
    */
   stk500_drain(pgm, 0);
 
+  // Initialization sequence for programming the external FLASH on the Prusa MK3
+  if (prusa_init_external_flash(pgm) < 0) {
+    avrdude_message(MSG_INFO, "%s: arduino_open(): Failed to initialize MK3 external flash programming mode\n", progname);
+    return -1;
+  }
+
   if (stk500_getsync(pgm) < 0)
     return -1;
 
diff --git a/xs/src/avrdude/avrdude-slic3r.cpp b/xs/src/avrdude/avrdude-slic3r.cpp
index a859200fb..030353413 100644
--- a/xs/src/avrdude/avrdude-slic3r.cpp
+++ b/xs/src/avrdude/avrdude-slic3r.cpp
@@ -1,5 +1,6 @@
 #include "avrdude-slic3r.hpp"
 
+#include <deque>
 #include <thread>
 
 extern "C" {
@@ -33,17 +34,22 @@ static void avrdude_progress_handler_closure(const char *task, unsigned progress
 struct AvrDude::priv
 {
 	std::string sys_config;
-	std::vector<std::string> args;
+	std::deque<std::vector<std::string>> args;
+	size_t current_args_set = 0;
+	RunFn run_fn;
 	MessageFn message_fn;
 	ProgressFn progress_fn;
 	CompleteFn complete_fn;
 
 	std::thread avrdude_thread;
 
+	priv(std::string &&sys_config) : sys_config(sys_config) {}
+
+	int run_one(const std::vector<std::string> &args);
 	int run();
 };
 
-int AvrDude::priv::run() {
+int AvrDude::priv::run_one(const std::vector<std::string> &args) {
 	std::vector<char*> c_args {{ const_cast<char*>(PACKAGE_NAME) }};
 	for (const auto &arg : args) {
 		c_args.push_back(const_cast<char*>(arg.data()));
@@ -68,10 +74,22 @@ int AvrDude::priv::run() {
 	return res;
 }
 
+int AvrDude::priv::run() {
+	for (; args.size() > 0; current_args_set++) {
+		int res = run_one(args.front());
+		args.pop_front();
+		if (res != 0) {
+			return res;
+		}
+	}
+
+	return 0;
+}
+
 
 // Public
 
-AvrDude::AvrDude() : p(new priv()) {}
+AvrDude::AvrDude(std::string sys_config) : p(new priv(std::move(sys_config))) {}
 
 AvrDude::AvrDude(AvrDude &&other) : p(std::move(other.p)) {}
 
@@ -82,15 +100,15 @@ AvrDude::~AvrDude()
 	}
 }
 
-AvrDude& AvrDude::sys_config(std::string sys_config)
+AvrDude& AvrDude::push_args(std::vector<std::string> args)
 {
-	if (p) { p->sys_config = std::move(sys_config); }
+	if (p) { p->args.push_back(std::move(args)); }
 	return *this;
 }
 
-AvrDude& AvrDude::args(std::vector<std::string> args)
+AvrDude& AvrDude::on_run(RunFn fn)
 {
-	if (p) { p->args = std::move(args); }
+	if (p) { p->run_fn = std::move(fn); }
 	return *this;
 }
 
@@ -123,11 +141,17 @@ AvrDude::Ptr AvrDude::run()
 
 	if (self->p) {
 		auto avrdude_thread = std::thread([self]() {
-				auto res = self->p->run();
-				if (self->p->complete_fn) {
-					self->p->complete_fn(res);
-				}
-			});
+			if (self->p->run_fn) {
+				self->p->run_fn();
+			}
+
+			auto res = self->p->run();
+
+			if (self->p->complete_fn) {
+				self->p->complete_fn(res, self->p->current_args_set);
+			}
+		});
+
 		self->p->avrdude_thread = std::move(avrdude_thread);
 	}
 
diff --git a/xs/src/avrdude/avrdude-slic3r.hpp b/xs/src/avrdude/avrdude-slic3r.hpp
index 8d881b094..273aa2378 100644
--- a/xs/src/avrdude/avrdude-slic3r.hpp
+++ b/xs/src/avrdude/avrdude-slic3r.hpp
@@ -12,22 +12,28 @@ class AvrDude
 {
 public:
 	typedef std::shared_ptr<AvrDude> Ptr;
+	typedef std::function<void()> RunFn;
 	typedef std::function<void(const char * /* msg */, unsigned /* size */)> MessageFn;
 	typedef std::function<void(const char * /* task */, unsigned /* progress */)> ProgressFn;
-	typedef std::function<void(int /* exit status */)> CompleteFn;
+	typedef std::function<void(int /* exit status */, size_t /* args_id */)> CompleteFn;
 
-	AvrDude();
+	// Main c-tor, sys_config is the location of avrdude's main configuration file
+	AvrDude(std::string sys_config);
 	AvrDude(AvrDude &&);
 	AvrDude(const AvrDude &) = delete;
 	AvrDude &operator=(AvrDude &&) = delete;
 	AvrDude &operator=(const AvrDude &) = delete;
 	~AvrDude();
 
-	// Set location of avrdude's main configuration file
-	AvrDude& sys_config(std::string sys_config);
+	// Push a set of avrdude cli arguments
+	// Each set makes one avrdude invocation - use this method multiple times to push
+	// more than one avrdude invocations.
+	AvrDude& push_args(std::vector<std::string> args);
 
-	// Set avrdude cli arguments
-	AvrDude& args(std::vector<std::string> args);
+	// Set a callback to be called just after run() before avrdude is ran
+	// This can be used to perform any needed setup tasks from the background thread.
+	// This has no effect when using run_sync().
+	AvrDude& on_run(RunFn fn);
 
 	// Set message output callback
 	AvrDude& on_message(MessageFn fn);
@@ -36,7 +42,10 @@ public:
 	// Progress is reported per each task (reading / writing) in percents.
 	AvrDude& on_progress(ProgressFn fn);
 
-	// Called when avrdude's main function finishes
+	// Called when the last avrdude invocation finishes with the exit status of zero,
+	// or earlier, if one of the invocations return a non-zero status.
+	// The second argument contains the sequential id of the last avrdude invocation argument set.
+	// This has no effect when using run_sync().
 	AvrDude& on_complete(CompleteFn fn);
 
 	int run_sync();
diff --git a/xs/src/avrdude/avrpart.c b/xs/src/avrdude/avrpart.c
index 621a85b98..b04851ac1 100644
--- a/xs/src/avrdude/avrpart.c
+++ b/xs/src/avrdude/avrpart.c
@@ -378,7 +378,7 @@ void avr_mem_display(const char * prefix, FILE * f, AVRMEM * m, int type,
   char * optr;
 
   if (m == NULL) {
-      fprintf(f,
+      avrdude_message(MSG_INFO,
               "%s                       Block Poll               Page                       Polled\n"
               "%sMemory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack\n"
               "%s----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------\n",
@@ -386,13 +386,13 @@ void avr_mem_display(const char * prefix, FILE * f, AVRMEM * m, int type,
   }
   else {
     if (verbose > 2) {
-      fprintf(f,
+      avrdude_message(MSG_INFO,
               "%s                       Block Poll               Page                       Polled\n"
               "%sMemory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack\n"
               "%s----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------\n",
               prefix, prefix, prefix);
     }
-    fprintf(f,
+    avrdude_message(MSG_INFO,
             "%s%-11s %4d %5d %5d %4d %-6s %6d %4d %6d %5d %5d 0x%02x 0x%02x\n",
             prefix, m->desc, m->mode, m->delay, m->blocksize, m->pollindex,
             m->paged ? "yes" : "no",
@@ -415,7 +415,7 @@ void avr_mem_display(const char * prefix, FILE * f, AVRMEM * m, int type,
               optr = avr_op_str(i);
             else
               optr = " ";
-          fprintf(f,
+          avrdude_message(MSG_INFO,
                   "%s    %-11s  %8d  %8s  %5d  %5d\n",
                   prefix, optr, j,
                   bittype(m->op[i]->bit[j].type),
@@ -620,7 +620,7 @@ void avr_display(FILE * f, AVRPART * p, const char * prefix, int verbose)
   LNODEID ln;
   AVRMEM * m;
 
-  fprintf(f,
+  avrdude_message(MSG_INFO,
           "%sAVR Part                      : %s\n"
           "%sChip Erase delay              : %d us\n"
           "%sPAGEL                         : P%02X\n"
diff --git a/xs/src/avrdude/fileio.c b/xs/src/avrdude/fileio.c
index f2d617823..aa57f5587 100644
--- a/xs/src/avrdude/fileio.c
+++ b/xs/src/avrdude/fileio.c
@@ -45,6 +45,8 @@
 
 #define MAX_LINE_LEN 256  /* max line length for ASCII format input files */
 
+#define MAX_MODE_LEN 32  // For fopen_and_seek()
+
 
 struct ihexrec {
   unsigned char    reclen;
@@ -96,8 +98,40 @@ static int fileio_num(struct fioparms * fio,
 		char * filename, FILE * f, AVRMEM * mem, int size,
 		FILEFMT fmt);
 
-static int fmt_autodetect(char * fname);
+static int fmt_autodetect(char * fname, size_t offset);
+
+
+
+static FILE *fopen_and_seek(const char *filename, const char *mode, size_t offset)
+{
+  FILE *file;
+  // On Windows we need to convert the filename to UTF-16
+#if defined(WIN32NATIVE)
+  static wchar_t fname_buffer[PATH_MAX];
+  static wchar_t mode_buffer[MAX_MODE_LEN];
+
+  if (MultiByteToWideChar(CP_UTF8, 0, filename, -1, fname_buffer, PATH_MAX) == 0) { return NULL; }
+  if (MultiByteToWideChar(CP_ACP, 0, mode, -1, mode_buffer, MAX_MODE_LEN) == 0) { return NULL; }
+
+  file = _wfopen(fname_buffer, mode_buffer);
+#else
+  file = fopen(filename, mode);
+#endif
+
+  if (file != NULL) {
+    // Some systems allow seeking past the end of file, so we need check for that first and disallow
+    if (fseek(file, 0, SEEK_END) != 0
+      || offset >= ftell(file)
+      || fseek(file, offset, SEEK_SET) != 0
+      ) {
+      fclose(file);
+      file = NULL;
+      errno = EINVAL;
+    }
+  }
 
+  return file;
+}
 
 
 char * fmtstr(FILEFMT format)
@@ -1358,7 +1392,7 @@ int fileio_setparms(int op, struct fioparms * fp,
 
 
 
-static int fmt_autodetect(char * fname)
+static int fmt_autodetect(char * fname, size_t offset)
 {
   FILE * f;
   unsigned char buf[MAX_LINE_LEN];
@@ -1368,10 +1402,11 @@ static int fmt_autodetect(char * fname)
   int first = 1;
 
 #if defined(WIN32NATIVE)
-  f = fopen(fname, "r");
+  f = fopen_and_seek(fname, "r", offset);
 #else
-  f = fopen(fname, "rb");
+  f = fopen_and_seek(fname, "rb", offset);
 #endif
+
   if (f == NULL) {
     avrdude_message(MSG_INFO, "%s: error opening %s: %s\n",
             progname, fname, strerror(errno));
@@ -1445,7 +1480,7 @@ static int fmt_autodetect(char * fname)
 
 
 int fileio(int op, char * filename, FILEFMT format, 
-             struct avrpart * p, char * memtype, int size)
+             struct avrpart * p, char * memtype, int size, size_t offset)
 {
   int rc;
   FILE * f;
@@ -1477,15 +1512,17 @@ int fileio(int op, char * filename, FILEFMT format,
   using_stdio = 0;
 
   if (strcmp(filename, "-")==0) {
-    if (fio.op == FIO_READ) {
-      fname = "<stdin>";
-      f = stdin;
-    }
-    else {
-      fname = "<stdout>";
-      f = stdout;
-    }
-    using_stdio = 1;
+    return -1;
+    // Note: we don't want to read stdin or write to stdout as part of Slic3r
+    // if (fio.op == FIO_READ) {
+    //   fname = "<stdin>";
+    //   f = stdin;
+    // }
+    // else {
+    //   fname = "<stdout>";
+    //   f = stdout;
+    // }
+    // using_stdio = 1;
   }
   else {
     fname = filename;
@@ -1502,7 +1539,7 @@ int fileio(int op, char * filename, FILEFMT format,
       return -1;
     }
 
-    format_detect = fmt_autodetect(fname);
+    format_detect = fmt_autodetect(fname, offset);
     if (format_detect < 0) {
       avrdude_message(MSG_INFO, "%s: can't determine file format for %s, specify explicitly\n",
                       progname, fname);
@@ -1533,7 +1570,7 @@ int fileio(int op, char * filename, FILEFMT format,
 
   if (format != FMT_IMM) {
     if (!using_stdio) {
-      f = fopen(fname, fio.mode);
+      f = fopen_and_seek(fname, fio.mode, offset);
       if (f == NULL) {
         avrdude_message(MSG_INFO, "%s: can't open %s file %s: %s\n",
                 progname, fio.iodesc, fname, strerror(errno));
diff --git a/xs/src/avrdude/libavrdude.h b/xs/src/avrdude/libavrdude.h
index e8197f9c2..536f1a2f7 100644
--- a/xs/src/avrdude/libavrdude.h
+++ b/xs/src/avrdude/libavrdude.h
@@ -737,7 +737,7 @@ extern bool cancel_flag;
 #define RETURN_IF_CANCEL() \
   do { \
     if (cancel_flag) { \
-      avrdude_message(MSG_INFO, "%s(): Cancelled, exiting...\n", __func__); \
+      avrdude_message(MSG_INFO, "avrdude: %s(): Cancelled, exiting...\n", __func__); \
       return -99; \
     } \
   } while (0)
@@ -821,7 +821,7 @@ extern "C" {
 char * fmtstr(FILEFMT format);
 
 int fileio(int op, char * filename, FILEFMT format,
-           struct avrpart * p, char * memtype, int size);
+           struct avrpart * p, char * memtype, int size, size_t offset);
 
 #ifdef __cplusplus
 }
@@ -870,6 +870,7 @@ enum updateflags {
 typedef struct update_t {
   char * memtype;
   int    op;
+  size_t offset;
   char * filename;
   int    format;
 } UPDATE;
@@ -881,7 +882,7 @@ extern "C" {
 extern UPDATE * parse_op(char * s);
 extern UPDATE * dup_update(UPDATE * upd);
 extern UPDATE * new_update(int op, char * memtype, int filefmt,
-			   char * filename);
+			   char * filename, size_t offset);
 extern void free_update(UPDATE * upd);
 extern int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd,
 		 enum updateflags flags);
diff --git a/xs/src/avrdude/main.c b/xs/src/avrdude/main.c
index 0550ceff1..d4c34fe44 100644
--- a/xs/src/avrdude/main.c
+++ b/xs/src/avrdude/main.c
@@ -194,7 +194,7 @@ static void usage(void)
  "  -F                         Override invalid signature check.\n"
  "  -e                         Perform a chip erase.\n"
  "  -O                         Perform RC oscillator calibration (see AVR053). \n"
- "  -U <memtype>:r|w|v:<filename>[:format]\n"
+ "  -U <memtype>:r|w|v:<offset>:<filename>[:format]\n"
  "                             Memory operation specification.\n"
  "                             Multiple -U options are allowed, each request\n"
  "                             is performed in the order specified.\n"
@@ -374,7 +374,7 @@ static void list_parts(FILE * f, const char *prefix, LISTID avrparts)
 
 static int cleanup_main(int status)
 {
-    if (pgm_setup && pgm->teardown) {
+    if (pgm_setup && pgm != NULL && pgm->teardown) {
         pgm->teardown(pgm);
     }
 
diff --git a/xs/src/avrdude/ser_posix.c b/xs/src/avrdude/ser_posix.c
index 91b18e945..cb0fc0385 100644
--- a/xs/src/avrdude/ser_posix.c
+++ b/xs/src/avrdude/ser_posix.c
@@ -376,6 +376,10 @@ static int ser_recv(union filedescriptor *fd, unsigned char * buf, size_t buflen
     FD_SET(fd->ifd, &rfds);
 
     nfds = select(fd->ifd + 1, &rfds, NULL, NULL, &to2);
+    // FIXME: The timeout has different behaviour on Linux vs other Unices
+    // On Linux, the timeout is modified by subtracting the time spent,
+    // on OS X (for example), it is not modified.
+    // POSIX recommends re-initializing it before selecting.
     if (nfds == 0) {
       avrdude_message(MSG_NOTICE2, "%s: ser_recv(): programmer is not responding\n",
                         progname);
diff --git a/xs/src/avrdude/stk500.c b/xs/src/avrdude/stk500.c
index 5d2d3c1df..63deb228f 100644
--- a/xs/src/avrdude/stk500.c
+++ b/xs/src/avrdude/stk500.c
@@ -716,11 +716,14 @@ static int stk500_loadaddr(PROGRAMMER * pgm, AVRMEM * mem, unsigned int addr)
   }
 
   buf[0] = Cmnd_STK_LOAD_ADDRESS;
-  buf[1] = addr & 0xff;
-  buf[2] = (addr >> 8) & 0xff;
-  buf[3] = Sync_CRC_EOP;
-
-  stk500_send(pgm, buf, 4);
+  // Workaround for the infamous ';' bug in the Prusa3D usb to serial converter.
+  // Send the binary data by nibbles to avoid transmitting the ';' character.
+  buf[1] = addr & 0x0f;
+  buf[2] = addr & 0xf0;
+  buf[3] = (addr >> 8) & 0x0f;
+  buf[4] = (addr >> 8) & 0xf0;
+  buf[5] = Sync_CRC_EOP;
+  stk500_send(pgm, buf, 6);
 
   if (stk500_recv(pgm, buf, 1) < 0)
     return -1;
@@ -765,7 +768,9 @@ static int stk500_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
   int block_size;
   int tries;
   unsigned int n;
-  unsigned int i;
+  unsigned int i, j;
+  unsigned int prusa3d_semicolon_workaround_round = 0;
+  bool has_semicolon = false;
 
   if (strcmp(m->desc, "flash") == 0) {
     memtype = 'F';
@@ -806,44 +811,64 @@ static int stk500_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
     tries++;
     stk500_loadaddr(pgm, m, addr/a_div);
 
-    /* build command block and avoid multiple send commands as it leads to a crash
-        of the silabs usb serial driver on mac os x */
-    i = 0;
-    buf[i++] = Cmnd_STK_PROG_PAGE;
-    buf[i++] = (block_size >> 8) & 0xff;
-    buf[i++] = block_size & 0xff;
-    buf[i++] = memtype;
-    memcpy(&buf[i], &m->buf[addr], block_size);
-    i += block_size;
-    buf[i++] = Sync_CRC_EOP;
-    stk500_send( pgm, buf, i);
+    for (i = 0; i < n_bytes; ++ i)
+      if (m->buf[addr + i] == ';') {
+        has_semicolon = true;
+        break;
+      }
 
-    if (stk500_recv(pgm, buf, 1) < 0)
-      return -1;
-    if (buf[0] == Resp_STK_NOSYNC) {
-      if (tries > 33) {
-        avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): can't get into sync\n",
-                progname);
-        return -3;
+    for (prusa3d_semicolon_workaround_round = 0; prusa3d_semicolon_workaround_round < (has_semicolon ? 2 : 1); ++ prusa3d_semicolon_workaround_round) {
+      /* build command block and avoid multiple send commands as it leads to a crash
+          of the silabs usb serial driver on mac os x */
+      i = 0;
+      buf[i++] = Cmnd_STK_PROG_PAGE;
+      // Workaround for the infamous ';' bug in the Prusa3D usb to serial converter.
+      // Send the binary data by nibbles to avoid transmitting the ';' character.
+      buf[i++] = (block_size >> 8) & 0xf0;
+      buf[i++] = (block_size >> 8) & 0x0f;
+      buf[i++] = block_size & 0xf0;
+      buf[i++] = block_size & 0x0f;
+      buf[i++] = memtype;
+      if (has_semicolon) {
+        for (j = 0; j < block_size; ++i, ++ j) {
+          buf[i] = m->buf[addr + j];
+          if (buf[i] == ';')
+            buf[i] |= (prusa3d_semicolon_workaround_round ? 0xf0 : 0x0f);
+        }
+      } else {
+        memcpy(&buf[i], &m->buf[addr], block_size);
+        i += block_size;
+      }
+      buf[i++] = Sync_CRC_EOP;
+      stk500_send( pgm, buf, i);
+
+      if (stk500_recv(pgm, buf, 1) < 0)
+        return -1;
+      if (buf[0] == Resp_STK_NOSYNC) {
+        if (tries > 33) {
+          avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): can't get into sync\n",
+                  progname);
+          return -3;
+        }
+        if (stk500_getsync(pgm) < 0)
+          return -1;
+        goto retry;
+      }
+      else if (buf[0] != Resp_STK_INSYNC) {
+        avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): (a) protocol error, "
+                        "expect=0x%02x, resp=0x%02x\n",
+                        progname, Resp_STK_INSYNC, buf[0]);
+        return -4;
+      }
+      
+      if (stk500_recv(pgm, buf, 1) < 0)
+        return -1;
+      if (buf[0] != Resp_STK_OK) {
+        avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): (a) protocol error, "
+                        "expect=0x%02x, resp=0x%02x\n",
+                        progname, Resp_STK_INSYNC, buf[0]);
+        return -5;
       }
-      if (stk500_getsync(pgm) < 0)
-	return -1;
-      goto retry;
-    }
-    else if (buf[0] != Resp_STK_INSYNC) {
-      avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): (a) protocol error, "
-                      "expect=0x%02x, resp=0x%02x\n",
-                      progname, Resp_STK_INSYNC, buf[0]);
-      return -4;
-    }
-    
-    if (stk500_recv(pgm, buf, 1) < 0)
-      return -1;
-    if (buf[0] != Resp_STK_OK) {
-      avrdude_message(MSG_INFO, "\n%s: stk500_paged_write(): (a) protocol error, "
-                      "expect=0x%02x, resp=0x%02x\n",
-                      progname, Resp_STK_INSYNC, buf[0]);
-      return -5;
     }
   }
 
@@ -893,11 +918,15 @@ static int stk500_paged_load(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
     tries++;
     stk500_loadaddr(pgm, m, addr/a_div);
     buf[0] = Cmnd_STK_READ_PAGE;
-    buf[1] = (block_size >> 8) & 0xff;
-    buf[2] = block_size & 0xff;
-    buf[3] = memtype;
-    buf[4] = Sync_CRC_EOP;
-    stk500_send(pgm, buf, 5);
+    // Workaround for the infamous ';' bug in the Prusa3D usb to serial converter.
+    // Send the binary data by nibbles to avoid transmitting the ';' character.
+    buf[1] = (block_size >> 8) & 0xf0;
+    buf[2] = (block_size >> 8) & 0x0f;
+    buf[3] = block_size & 0xf0;
+    buf[4] = block_size & 0x0f;
+    buf[5] = memtype;
+    buf[6] = Sync_CRC_EOP;
+    stk500_send(pgm, buf, 7);
 
     if (stk500_recv(pgm, buf, 1) < 0)
       return -1;
diff --git a/xs/src/avrdude/stk500v2.c b/xs/src/avrdude/stk500v2.c
index d3acb639c..4d62640c0 100644
--- a/xs/src/avrdude/stk500v2.c
+++ b/xs/src/avrdude/stk500v2.c
@@ -79,7 +79,7 @@
 #define SERIAL_TIMEOUT 2
 
 // Retry count
-#define RETRIES 5
+#define RETRIES 0
 
 #if 0
 #define DEBUG(...) avrdude_message(MSG_INFO, __VA_ARGS__)
@@ -745,7 +745,7 @@ static int stk500v2_recv(PROGRAMMER * pgm, unsigned char *msg, size_t maxsize) {
 
 
 
-static int stk500v2_getsync_internal(PROGRAMMER * pgm, int retries) {
+int stk500v2_getsync(PROGRAMMER * pgm) {
   int tries = 0;
   unsigned char buf[1], resp[32];
   int status;
@@ -804,7 +804,7 @@ retry:
                         progname, pgmname[PDATA(pgm)->pgmtype]);
       return 0;
     } else {
-      if (tries > retries) {
+      if (tries > RETRIES) {
         avrdude_message(MSG_INFO, "%s: stk500v2_getsync(): can't communicate with device: resp=0x%02x\n",
                         progname, resp[0]);
         return -6;
@@ -814,7 +814,7 @@ retry:
 
   // or if we got a timeout
   } else if (status == -1) {
-    if (tries > retries) {
+    if (tries > RETRIES) {
       avrdude_message(MSG_INFO, "%s: stk500v2_getsync(): timeout communicating with programmer\n",
               progname);
       return -1;
@@ -823,7 +823,7 @@ retry:
 
   // or any other error
   } else {
-    if (tries > retries) {
+    if (tries > RETRIES) {
       avrdude_message(MSG_INFO, "%s: stk500v2_getsync(): error communicating with programmer: (%d)\n",
               progname,status);
     } else
@@ -833,11 +833,6 @@ retry:
   return 0;
 }
 
-int stk500v2_getsync(PROGRAMMER * pgm) {
-  // This is to avoid applying RETRIES exponentially
-  return stk500v2_getsync_internal(pgm, RETRIES);
-}
-
 static int stk500v2_command(PROGRAMMER * pgm, unsigned char * buf,
                             size_t len, size_t maxlen) {
   int i;
@@ -947,7 +942,7 @@ retry:
   }
 
   // otherwise try to sync up again
-  status = stk500v2_getsync_internal(pgm, 1);
+  status = stk500v2_getsync(pgm);
   if (status != 0) {
     if (tries > RETRIES) {
       avrdude_message(MSG_INFO, "%s: stk500v2_command(): failed miserably to execute command 0x%02x\n",
diff --git a/xs/src/avrdude/update.c b/xs/src/avrdude/update.c
index a73461dfa..e9dd6e325 100644
--- a/xs/src/avrdude/update.c
+++ b/xs/src/avrdude/update.c
@@ -101,6 +101,24 @@ UPDATE * parse_op(char * s)
 
   p++;
 
+  // Extension: Parse file contents offset
+  size_t offset = 0;
+
+  for (; *p != ':'; p++) {
+    if (*p >= '0' && *p <= '9') {
+      offset *= 10;
+      offset += *p - 0x30;
+    } else {
+      avrdude_message(MSG_INFO, "%s: invalid update specification: offset is not a number\n", progname);
+      free(upd->memtype);
+      free(upd);
+      return NULL;
+    }
+  }
+
+  upd->offset = offset;
+  p++;
+
   /*
    * Now, parse the filename component.  Instead of looking for the
    * leftmost possible colon delimiter, we look for the rightmost one.
@@ -176,7 +194,7 @@ UPDATE * dup_update(UPDATE * upd)
   return u;
 }
 
-UPDATE * new_update(int op, char * memtype, int filefmt, char * filename)
+UPDATE * new_update(int op, char * memtype, int filefmt, char * filename, size_t offset)
 {
   UPDATE * u;
 
@@ -190,6 +208,7 @@ UPDATE * new_update(int op, char * memtype, int filefmt, char * filename)
   u->filename = strdup(filename);
   u->op = op;
   u->format = filefmt;
+  u->offset = offset;
 
   return u;
 }
@@ -250,7 +269,7 @@ int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd, enum updateflags f
                       progname,
                       strcmp(upd->filename, "-")==0 ? "<stdout>" : upd->filename);
     }
-    rc = fileio(FIO_WRITE, upd->filename, upd->format, p, upd->memtype, size);
+    rc = fileio(FIO_WRITE, upd->filename, upd->format, p, upd->memtype, size, 0);
     if (rc < 0) {
       avrdude_message(MSG_INFO, "%s: write to file '%s' failed\n",
               progname, upd->filename);
@@ -267,7 +286,7 @@ int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd, enum updateflags f
                       progname,
                       strcmp(upd->filename, "-")==0 ? "<stdin>" : upd->filename);
     }
-    rc = fileio(FIO_READ, upd->filename, upd->format, p, upd->memtype, -1);
+    rc = fileio(FIO_READ, upd->filename, upd->format, p, upd->memtype, -1, upd->offset);
     if (rc < 0) {
       avrdude_message(MSG_INFO, "%s: read from file '%s' failed\n",
               progname, upd->filename);
@@ -296,11 +315,11 @@ int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd, enum updateflags f
       report_progress(1,1,NULL);
     }
     else {
-      /*
-       * test mode, don't actually write to the chip, output the buffer
-       * to stdout in intel hex instead
-       */
-      rc = fileio(FIO_WRITE, "-", FMT_IHEX, p, upd->memtype, size);
+      // /*
+      //  * test mode, don't actually write to the chip, output the buffer
+      //  * to stdout in intel hex instead
+      //  */
+      // rc = fileio(FIO_WRITE, "-", FMT_IHEX, p, upd->memtype, size, 0);
     }
 
     if (rc < 0) {
@@ -332,7 +351,7 @@ int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd, enum updateflags f
             progname, mem->desc, upd->filename);
     }
 
-    rc = fileio(FIO_READ, upd->filename, upd->format, p, upd->memtype, -1);
+    rc = fileio(FIO_READ, upd->filename, upd->format, p, upd->memtype, -1, upd->offset);
     if (rc < 0) {
       avrdude_message(MSG_INFO, "%s: read from file '%s' failed\n",
               progname, upd->filename);