Support for serial port "touch" functionality using libserialport

src/avrdude.1

@@ -29,6 +29,7 @@
 .Nm
 .Fl p Ar partno
 .Op Fl b Ar baudrate
+.Op Fl r
 .Op Fl B Ar bitclock
 .Op Fl c Ar programmer-id
 .Op Fl C Ar config-file
@@ -365,6 +366,11 @@ for more information run avrdude -p x/h.
 .It Fl b Ar baudrate
 Override the RS-232 connection baud rate specified in the respective
 programmer's entry of the configuration file.
+.It Fl r
+Opens the serial port at 1200 baud and immedeatly closes it, prior to
+establishing communication with the programmer. This is commonly knows as A
+"1200bps touch", and is used to trigger programming mode for certain boards
+like Arduino Leonardo, Arduino Micro/Pro Micro and the Arduino Nano Every.
 .It Fl B Ar bitclock
 Specify the bit clock period for the JTAG, PDI, TPI, UPDI, or ISP
 interface. The value is a floating-point number in microseconds.

src/doc/avrdude.texi

@@ -469,6 +469,12 @@ ATmega328P MCU properties; for more information run @code{avrdude -p x/h}.
 Override the RS-232 connection baud rate specified in the respective
 programmer's entry of the configuration file.
 
+@item -r @var{baudrate}
+Opens the serial port at 1200 baud and immedeatly closes it, prior to
+establishing communication with the programmer. This is commonly knows as A
+"1200bps touch", and is used to trigger programming mode for certain boards
+like Arduino Leonardo, Arduino Micro/Pro Micro and the Arduino Nano Every.
+
 @item -B @var{bitclock}
 Specify the bit clock period for the JTAG, PDI, TPI, UPDI, or ISP
 interface. The value is a floating-point number in microseconds.

src/libavrdude.h

@@ -1252,6 +1252,7 @@ extern "C" {
 int setport_from_serialadapter(char **portp, const SERIALADAPTER *ser, const char *sernum);
 int setport_from_vid_pid(char **portp, int vid, int pid, const char *sernum);
 int list_available_serialports(LISTID programmers);
+int touch_serialport(char **portp, int baudrate);
 
 int str_starts(const char *str, const char *starts);
 int str_eq(const char *str1, const char *str2);

src/main.c

@@ -228,6 +228,8 @@ static void usage(void)
     "  -p <wildcard>/<flags>  Run developer options for matched AVR devices,\n"
     "                         e.g., -p ATmega328P/s or /S for part definition\n"
     "  -b <baudrate>          Override RS-232 baud rate\n"
+    "  -r                     Open and close (\"touch\") the serial port at\n"
+    "                         1200 baud before establishing connection\n"
     "  -B <bitclock>          Specify bit clock period (us)\n"
     "  -C <config-file>       Specify location of configuration file\n"
     "  -c <programmer>        Specify programmer; -c ? and -c ?type list all\n"
@@ -526,6 +528,7 @@ int main(int argc, char * argv [])
   char  * e;           /* for strtod() error checking */
   const char  *errstr; /* for str_int() error checking */
   int     baudrate;    /* override default programmer baud rate */
+  bool    touch_1200bps = false; /* "touch" serial port prior to programming */
   double  bitclock;    /* Specify programmer bit clock (JTAG ICE) */
   int     ispdelay;    /* Specify the delay for ISP clock */
   int     init_ok;     /* Device initialization worked well */
@@ -635,7 +638,7 @@ int main(int argc, char * argv [])
   /*
    * process command line arguments
    */
-  while ((ch = getopt(argc,argv,"?Ab:B:c:C:DeE:Fi:l:np:OP:qstT:U:uvVx:yY:")) != -1) {
+  while ((ch = getopt(argc,argv,"?Ab:B:c:C:DeE:Fi:l:np:OP:qrstT:U:uvVx:yY:")) != -1) {
 
     switch (ch) {
       case 'b': /* override default programmer baud rate */
@@ -766,6 +769,10 @@ int main(int argc, char * argv [])
         quell_progress++ ;
         break;
 
+      case 'r' :
+        touch_1200bps = true;
+        break;
+
       case 't': /* enter terminal mode */
         ladd(updates, cmd_update("interactive terminal"));
         break;
@@ -1231,6 +1238,9 @@ int main(int argc, char * argv [])
       free(port_tok[i]);
   }
 
+  if(touch_1200bps && pgm->conntype == CONNTYPE_SERIAL)
+    touch_serialport(&port, 1200);
+
   /*
    * open the programmer
    */

src/serialadapter.c

@@ -21,6 +21,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "avrdude.h"
 #include "libavrdude.h"
@@ -130,6 +131,13 @@ static SERPORT *get_libserialport_data(int *np) {
   return sp;
 }
 
+// Free memory allocated from get_libserialport_data()
+static void free_libserialport_data(SERPORT *sp, int n) {
+  for(int k = 0; sp && k < n; k++)
+    free(sp[k].sernum), free(sp[k].port);
+  free(sp);
+}
+
 // Returns a NULL-terminated malloc'd list of items in SERPORT list spa that are not in spb
 SERPORT **sa_spa_not_spb(SERPORT *spa, int na, SERPORT *spb, int nb) {
   SERPORT **ret = cfg_malloc(__func__, (na+1)*sizeof*ret);
@@ -266,10 +274,7 @@ int setport_from_serialadapter(char **portp, const SERIALADAPTER *sea, const cha
       if(m == 0 || sa_num_matches_by_sea(sea, sernum, sp+i, 1) == 1)
         sa_print_specs(sp, n, i);
   }
-
-  for(int k = 0; k < n; k++)
-    free(sp[k].sernum), free(sp[k].port);
-  free(sp);
+  free_libserialport_data(sp, n);
 
   return rv;
 }
@@ -294,14 +299,53 @@ int setport_from_vid_pid(char **portp, int vid, int pid, const char *sernum) {
       if(m == 0 || sa_num_matches_by_ids(vid, pid, sernum, sp+i, 1) == 1)
         sa_print_specs(sp, n, i);
   }
-
-  for(int k = 0; k < n; k++)
-    free(sp[k].sernum), free(sp[k].port);
-  free(sp);
+  free_libserialport_data(sp, n);
 
   return rv;
 }
 
+// Potentially change port *portp after opening & closing it with baudrate
+int touch_serialport(char **portp, int baudrate) {
+  int i, n1, n2;
+  SERPORT *sp1, *sp2, **diff;
+  sp1 = get_libserialport_data(&n1);
+  if(!sp1 || n1 <= 0 || !portp)
+    return -1;
+
+  pmsg_info("touching serial port %s at %d baud\n", *portp, baudrate);
+  union pinfo pinfo;
+  union filedescriptor fd;
+  pinfo.serialinfo.baud = baudrate;
+  pinfo.serialinfo.cflags = SERIAL_8N1;
+  if(serial_open(*portp, pinfo, &fd) == -1) {
+    pmsg_error("%s() failed to open port %s at %d baud\n", __func__, *portp, baudrate);
+    return -1;
+  }
+  serial_set_dtr_rts(&fd, 0);
+  serial_close(&fd);
+
+  pmsg_info("waiting for new port...");
+  for(i = 10; i > 0; i--) {
+    usleep(80*1000);
+    if((sp2 = get_libserialport_data(&n2))) {
+      diff = sa_spa_not_spb(sp2, n2, sp1, n1);
+      if(*diff && diff[0]->port && !diff[1]) { // Exactly one new port sprung up
+        pmsg_notice("new port %s discovered\n", (*diff)->port);
+        if(*portp)
+          free(*portp);
+        *portp = cfg_strdup(__func__, (*diff)->port);
+        i = -1;                 // Leave loop
+      }
+      free(diff); 
+      free_libserialport_data(sp2, n2);
+    }
+  }
+  free_libserialport_data(sp1, n1);
+  msg_info(" using %s port %s\n", i<0? "new": "same", *portp);
+
+  return 0;
+}
+
 // List available serial ports
 int list_available_serialports(LISTID programmers) {
   // Get serial port information from libserialport
@@ -344,6 +388,11 @@ int list_available_serialports(LISTID programmers) {
   return -1;
 }
 
+int touch_serialport(char **portp, int baudrate) {
+  pmsg_error("avrdude built without libserialport support; please compile again with libserialport installed\n");
+  return -1;
+}
+
 #endif
 
 void list_serialadapters(FILE *fp, const char *prefix, LISTID programmers) {