3 files changed, 14 insertions, 3 deletions
diff --git a/cmd.c b/cmd.c
index a460808..29bc8c9 100644
--- a/cmd.c
+++ b/cmd.c
@@ -195,7 +195,11 @@ cmd_write(int fd, const struct command *cmd, int argc, char **args)
             }
         }
 
-        puts("\nDone!");
+        putchar('\n');
+
+        if (!err)
+            puts("Done!");
+
         fclose(fp);
     } else if (param.human_readable) {
         do {
diff --git a/serial.c b/serial.c
index 5f7548c..82a5abd 100644
--- a/serial.c
+++ b/serial.c
@@ -206,6 +206,9 @@ read_buf(int fd, size_t len, void *_buf)
         } else {
             write_ack(fd, NACK);
         }
+
+        /* Wait 2 ms between attempts */
+        usleep(2000);
     }
 
     err = ERR_NACK;
@@ -249,6 +252,9 @@ write_buf(int fd, size_t len, const void *_buf)
 
         if (err != NACK)
             goto error;
+
+        /* Wait 2 ms between attempts */
+        usleep(2000);
     }
 
 error:
diff --git a/zup.c b/zup.c
index 5fe1e61..e7f8fe6 100644
--- a/zup.c
+++ b/zup.c
@@ -128,7 +128,7 @@ parse_options(int argc, char *const argv[])
         case 'a':
             errno = 0;
             param.max_attempts = strtoul(optarg, NULL, 10);
-            if (errno) {
+            if (errno || !optarg || strlen(optarg) == 0) {
                 perror("Invalid attempts number\n");
                 exit(EXIT_FAILURE);
             }
@@ -232,7 +232,8 @@ struct param param = {
     .verbose = 0,
     .human_readable = 0,
     .repl = 0,
-    .show_progress = 0
+    .show_progress = 0,
+    .max_attempts = 5
 };
 
 // TODO: Support stdin/stdout