Work around data transfer problems in FTDI serial converters

Fix glitches in FPGA viewer part

1 files changed, 27 insertions, 5 deletions

diff --git a/servers/fpga_server_lin/src/fpga_conn.cpp b/servers/fpga_server_lin/src/fpga_conn.cpp
index 0570cff..ed4c012 100644
--- a/servers/fpga_server_lin/src/fpga_conn.cpp
+++ b/servers/fpga_server_lin/src/fpga_conn.cpp
@@ -29,10 +29,12 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <fcntl.h>
+#include <errno.h>
 #include <termios.h>
 #include <unistd.h>
 #include <sys/signal.h>
 #include <sys/types.h>
+#include <sys/ioctl.h>
 
 #include <tqtimer.h>
 
@@ -40,6 +42,10 @@
 
 #include "fpga_conn.h"
 
+#define FLUSH_IN	0
+#define FLUSH_OUT	1
+#define FLUSH_BOTH	2
+
 #define ABORT_SOCKET(s) 		s->close();						\
 					s->disconnect();					\
 					delete s;						\
@@ -195,14 +201,15 @@ int FPGASocket::setupSerial() {
 
 void FPGASocket::commandLoop() {
 	int cc;
-	char buffer[10000];
+	int ret;
+	char buffer[1024];
 	bool transferred_data;
 
 	m_criticalSection++;
 	try {
 		transferred_data = false;
 		if (state() == TQSocket::Connected) {
-			cc = read(m_fd_tty, buffer, 10000);
+			cc = read(m_fd_tty, buffer, 1024);
 			if (cc > 0) {
 				writeBlock(buffer, cc);
 				flush();
@@ -210,11 +217,26 @@ void FPGASocket::commandLoop() {
 				printf("[DEBUG] Got %d bytes from the serial port\n\r", cc); fflush(stdout);
 			}
 			if (canReadData()) {
-				cc = readBlock(buffer, 10000);
+				cc = readBlock(buffer, 1024);
 				if (cc > 0) {
-					if (write(m_fd_tty, buffer, cc) < 0) {
+					ret = write(m_fd_tty, buffer, cc);
+
+					// HACK
+					// This works around a buffer overflow on FTDI serial devices
+					// It may not be sufficient for baudrates less than 115200!
+					if (cc > 128) {
+						usleep(100000);
+					}
+
+					while ((ret < 0) && (errno == EAGAIN)) {
+						usleep(1000);
+						ret = write(m_fd_tty, buffer, cc);
+					}
+					if (ret < 0) {
 						// ERROR
+						printf("[ERROR] Failed to transmit data to serial port (%s, code %d)!  Continuing, but data was likely lost\n\r", strerror(errno), errno); fflush(stdout);
 					}
+					ioctl(m_fd_tty, TCFLSH, FLUSH_OUT);
 					transferred_data = true;
 					printf("[DEBUG] Got %d bytes from the network interface\n\r", cc); fflush(stdout);
 				}
@@ -280,4 +302,4 @@ void FPGAServer::newConnection(int socket) {
 
 void FPGAServer::remoteConnectionClosed() {
 	m_numberOfConnections--;
-}
\ No newline at end of file
+}