Add -xno_autoreset for the -c arduino programmer

src/arduino.c

@@ -37,6 +37,45 @@
 #include "stk500.h"
 #include "arduino.h"
 
+static int arduino_parseextparms(const PROGRAMMER *pgm, const LISTID extparms) {
+  const char *extended_param;
+  int attempts;
+  int rv = 0;
+
+  for (LNODEID ln = lfirst(extparms); ln; ln = lnext(ln)) {
+    extended_param = ldata(ln);
+
+    if (sscanf(extended_param, "attempts=%2d", &attempts) == 1) {
+      PDATA(pgm)->retry_attempts = attempts;
+      pmsg_info("setting number of retry attempts to %d\n", attempts);
+      continue;
+    }
+
+    if(str_starts(extended_param, "no_autoreset")) {
+      if(!str_eq(extended_param, "no_autoreset")) {
+        pmsg_error("invalid -xno_autoreset value %s. Use -xno_autoreset\n", extended_param);
+        rv = -1;
+        break;
+      }
+      PDATA(pgm)->autoreset = false;
+      continue;
+    }
+
+    if (str_eq(extended_param, "help")) {
+      msg_error("%s -c %s extended options:\n", progname, pgmid);
+      msg_error("  -xattempts=<arg> Specify no. connection retry attempts\n");
+      msg_error("  -xno_autoreset   Don't toggle RTS/DTR lines on port open to prevent a hardware reset\n");
+      msg_error("  -xhelp           Show this help menu and exit\n");
+      return LIBAVRDUDE_EXIT;
+    }
+
+    pmsg_error("invalid extended parameter '%s'\n", extended_param);
+    rv = -1;
+  }
+
+  return rv;
+}
+
 /* read signature bytes - arduino version */
 static int arduino_read_sig_bytes(const PROGRAMMER *pgm, const AVRPART *p, const AVRMEM *m) {
   unsigned char buf[32];
@@ -85,28 +124,28 @@ static int arduino_open(PROGRAMMER *pgm, const char *port) {
     return -1;
   }
 
-  // This code assumes a negative-logic USB to TTL serial adapter
-  // Set RTS/DTR high to discharge the series-capacitor, if present
-  serial_set_dtr_rts(&pgm->fd, 0);
-  /*
-   * Long wait needed for optiboot: otherwise the second of two bootloader
-   * calls in quick succession fails:
-   *
-   * avrdude -c arduino -qqp m328p -U x.hex; avrdude -c arduino -qqp m328p -U x.hex
-   */
-  usleep(250 * 1000);
-  // Pull the RTS/DTR line low to reset AVR
-  serial_set_dtr_rts(&pgm->fd, 1);
-  // Max 100 us: charging a cap longer creates a high reset spike above Vcc
-  usleep(100);
-  // Set the RTS/DTR line back to high, so direct connection to reset works
-  serial_set_dtr_rts(&pgm->fd, 0);
+  if(PDATA(pgm)->autoreset) {
+    // This code assumes a negative-logic USB to TTL serial adapter
+    // Set RTS/DTR high to discharge the series-capacitor, if present
+    serial_set_dtr_rts(&pgm->fd, 0);
+    /*
+    * Long wait needed for optiboot: otherwise the second of two bootloader
+    * calls in quick succession fails:
+    *
+    * avrdude -c arduino -qqp m328p -U x.hex; avrdude -c arduino -qqp m328p -U x.hex
+    */
+    usleep(250 * 1000);
+    // Pull the RTS/DTR line low to reset AVR
+    serial_set_dtr_rts(&pgm->fd, 1);
+    // Max 100 us: charging a cap longer creates a high reset spike above Vcc
+    usleep(100);
+    // Set the RTS/DTR line back to high, so direct connection to reset works
+    serial_set_dtr_rts(&pgm->fd, 0);
 
-  usleep(100 * 1000);
+    usleep(100 * 1000);
+  }
 
-  /*
-   * drain any extraneous input
-   */
+  // Drain any extraneous input
   stk500_drain(pgm, 0);
 
   if (stk500_getsync(pgm) < 0)
@@ -115,7 +154,7 @@ static int arduino_open(PROGRAMMER *pgm, const char *port) {
   return 0;
 }
 
-static void arduino_close(PROGRAMMER * pgm)
+static void arduino_close(PROGRAMMER *pgm)
 {
   serial_close(&pgm->fd);
   pgm->fd.ifd = -1;
@@ -131,9 +170,12 @@ void arduino_initpgm(PROGRAMMER *pgm) {
   stk500_initpgm(pgm);
 
   strcpy(pgm->type, "Arduino");
+  PDATA(&pgm)->autoreset = true; // Auto-reset enabled by default
+
   pgm->read_sig_bytes = arduino_read_sig_bytes;
   pgm->open = arduino_open;
   pgm->close = arduino_close;
+  pgm->parseextparams = arduino_parseextparms;
 
   cx->avr_disableffopt = 1;     // Disable trailing 0xff removal
 }

src/stk500.c

@@ -116,7 +116,7 @@ int stk500_getsync(const PROGRAMMER *pgm) {
 
   for (attempt = 0; attempt < max_sync_attempts; attempt++) {
     // Restart Arduino bootloader for every sync attempt
-    if (str_eq(pgm->type, "Arduino") && attempt > 0) {
+    if (PDATA(pgm)->autoreset && attempt > 0) {
       // This code assumes a negative-logic USB to TTL serial adapter
       // Pull the RTS/DTR line low to reset AVR: it is still high from open()/last attempt
       serial_set_dtr_rts(&pgm->fd, 1);

src/stk500.h

@@ -60,6 +60,9 @@ struct pdata {
   double fosc_data;
 
   unsigned xtal;                // Set STK500 XTAL frequency
+
+  // Flag to enable/disable autoreset for the arduino programmer
+  bool autoreset;
 };
 
 #define PDATA(pgm) ((struct pdata *)(pgm->cookie))