make desktop serial more responsive

libraries/Desktop/support/FastSerial.cpp

@@ -45,6 +45,7 @@
 #include <sys/types.h> 
 #include <sys/socket.h>
 #include <netinet/in.h>
+#include "desktop.h"
 
 #define LISTEN_BASE_PORT 5760
 #define BUFFER_SIZE 128
@@ -305,3 +306,19 @@ void FastSerial::_freeBuffer(Buffer *buffer)
 {
 }
 
+/*
+  return true if any bytes are pending
+ */
+void desktop_serial_select_setup(fd_set *fds, int *fd_high)
+{
+	int i;
+
+	for (i=0; i<FS_MAX_PORTS; i++) {
+		if (tcp_state[i].connected) {
+			FD_SET(tcp_state[i].fd, fds);
+			if (tcp_state[i].fd > *fd_high) {
+				*fd_high = tcp_state[i].fd;
+			}
+		}
+	}
+}

libraries/Desktop/support/main.cpp

@@ -4,6 +4,7 @@
 #include <sys/time.h>
 #include <sched.h>
 #include <wiring.h>
+#include "desktop.h"
 
 void setup(void);
 void loop(void);
@@ -16,15 +17,17 @@ int main(void)
 	setup();
 	while (true) {
 		struct timeval tv;
-		unsigned long t1, t2;
+		fd_set fds;
-		t1 = micros();
+		int fd_high = 0;
+
+		FD_ZERO(&fds);
 		loop();
-		t2 = micros();
+
-		if (t2 - t1 < 2) {
+		desktop_serial_select_setup(&fds, &fd_high);
-			tv.tv_sec = 0;
+		tv.tv_sec = 0;
-			tv.tv_usec = 1;
+		tv.tv_usec = 100;
-			select(0, NULL, NULL, NULL, &tv);
+
-		}
+		select(fd_high+1, &fds, NULL, NULL, &tv);
 	}
 	return 0;
 }