Added sprog_waitdata(), check if device was previously synchronized

If we don't receive the response, send '\r\n' and check if the reply is '?\r\n'. If so, the device might be already synchronized, so receive 'Invalid command' and skip the rest of the synchronization

lpc.c

@@ -60,22 +60,31 @@ void lpc_init(struct lpc_device *dev) {
   char buf[4096];
   printf("?");
   fflush(stdout);
-  fgets(buf, sizeof(buf), stdin);
-  if(strcmp(buf, "Synchronized\r\n")==0)
-    sprog_error("Synchronization successful\n");
-  printf("Synchronized\r\n");
-  fflush(stdout);
-  fgets(buf, sizeof(buf), stdin); /* deny echoed line */
-  fgets(buf, sizeof(buf), stdin);
-  if(strcmp(buf, "OK\r\n")!=0)
-    sprog_error("Expected OK, received '%s'\n", buf);
-  sprog_error("Sending clock frequency\n");
-  printf("12000\r\n");
-  fflush(stdout);
-  fgets(buf, sizeof(buf), stdin); /* deny echoed line */
-  fgets(buf, sizeof(buf), stdin);
-  if(strcmp(buf, "OK\r\n")!=0)
-    sprog_error("Expected OK, received '%s'\n", buf);
+  if(sprog_waitdata(500)==0) {
+    printf("\r\n");
+    fflush(stdout);
+    fgets(buf, sizeof(buf), stdin);
+    if(strcmp(buf, "?\r\n")==0)
+      sprog_error("The device appears to be already synchronized\n");
+      fgets(buf, sizeof(buf), stdin); /* deny invalid command reply */
+  } else {
+    fgets(buf, sizeof(buf), stdin);
+    if(strcmp(buf, "Synchronized\r\n")==0)
+      sprog_error("Synchronization successful\n");
+    printf("Synchronized\r\n");
+    fflush(stdout);
+    fgets(buf, sizeof(buf), stdin); /* deny echoed line */
+    fgets(buf, sizeof(buf), stdin);
+    if(strcmp(buf, "OK\r\n")!=0)
+      sprog_error("Expected OK, received '%s'\n", buf);
+    sprog_error("Sending clock frequency\n");
+    printf("12000\r\n");
+    fflush(stdout);
+    fgets(buf, sizeof(buf), stdin); /* deny echoed line */
+    fgets(buf, sizeof(buf), stdin);
+    if(strcmp(buf, "OK\r\n")!=0)
+      sprog_error("Expected OK, received '%s'\n", buf);
+  }
   sprog_error("Reading part ID\n");
   if(lpc_read_partid(dev)==0)
     sprog_error("Found device: %s, %dkB Flash, %dkB RAM\n", dev->part->name, dev->part->flash, dev->part->ram);

sprog.c

@@ -4,6 +4,7 @@
 #include <errno.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <sys/select.h>
 #include <sprog.h>
 
 void sprog_process(const struct sprog_family *fam, void *arg, int nstdin, int nstdout);
@@ -47,6 +48,18 @@ void sprog_communicate(const struct sprog_family *fam, const char *port, int bau
   }
 }
 
+int sprog_waitdata(int timeout) {
+  fd_set read_set;
+  struct timeval tval;
+  FD_ZERO(&read_set);
+  FD_SET(1, &read_set);
+  tval.tv_sec = timeout/1000;
+  tval.tv_usec = (timeout%1000)*1000;
+  if(select(1+1, &read_set, NULL, NULL, &tval)!=1)
+    return 0;
+  return 1;
+}
+
 void sprog_process(const struct sprog_family *fam, void *arg, int nstdin, int nstdout) {
   dup2(nstdin, 0);
   dup2(nstdout, 1);

sprog.h

@@ -15,6 +15,7 @@ extern const char sprog_version[];
 void sprog_communicate(const struct sprog_family *fam, const char *port, int baud);
 void sprog_process(const struct sprog_family *fam, void *arg, int nstdin, int nstdout);
 int sprog_getline(char *buf, int len, int timeout);
+int sprog_waitdata(int timeout);
 void sprog_error(const char *text, ...);
 void sprog_sleep(int msec);