diff --git a/can_structs.h b/can_structs.h
index b45034e..d9fa1c5 100644
--- a/can_structs.h
+++ b/can_structs.h
@@ -11,7 +11,7 @@ public:
     int bus;
     bool extended;
     bool isReceived; //did we receive this or send it?
-    int len;
+    uint32_t len;
     unsigned char data[8];
     uint64_t timestamp;
 };
diff --git a/canframemodel.cpp b/canframemodel.cpp
index 02fc0cf..f1a3b64 100644
--- a/canframemodel.cpp
+++ b/canframemodel.cpp
@@ -207,7 +207,7 @@ QVariant CANFrameModel::data(const QModelIndex &index, int role) const
             return QString::number(thisFrame.len);
             break;
         case 6: //data
-            for (int i = 0; i < thisFrame.len; i++)
+            for (unsigned int i = 0; i < thisFrame.len; i++)
             {
                 tempString.append(Utility::formatNumber(thisFrame.data[i]));
                 tempString.append(" ");
diff --git a/filecomparatorwindow.cpp b/filecomparatorwindow.cpp
index 83f120e..c7aeea2 100644
--- a/filecomparatorwindow.cpp
+++ b/filecomparatorwindow.cpp
@@ -112,7 +112,7 @@ void FileComparatorWindow::calculateDetails()
         CANFrame frame = interestedFrames.at(x);
         if (interestedIDs.contains(frame.ID)) //if we saw this ID before then add to the QList in there
         {
-            for (int y = 0; y < frame.len; y++)
+            for (unsigned int y = 0; y < frame.len; y++)
             {
                 interestedIDs[frame.ID].values[y][frame.data[y]]++;
                 tmp = frame.data[y];
@@ -137,7 +137,7 @@ void FileComparatorWindow::calculateDetails()
                 }
             }
             //memset(newData->values, 0, 256 * 8);
-            for (int y = 0; y < frame.len; y++)
+            for (unsigned int y = 0; y < frame.len; y++)
             {
                 newData->values[y][frame.data[y]] = 1;
                 tmp = frame.data[y];
@@ -177,7 +177,7 @@ void FileComparatorWindow::calculateDetails()
                 }
             }
             //memset(newData->values, 0, 256 * 8);
-            for (int y = 0; y < frame.len; y++)
+            for (unsigned int y = 0; y < frame.len; y++)
             {
                 newData->values[y][frame.data[y]] = 1;
                 tmp = frame.data[y];
diff --git a/framefileio.cpp b/framefileio.cpp
index 2e96149..94c612d 100644
--- a/framefileio.cpp
+++ b/framefileio.cpp
@@ -322,7 +322,7 @@ bool FrameFileIO::loadCRTDFile(QString filename, QVector<CANFrame>* frames)
                         else thisFrame.isReceived = true;
                     thisFrame.bus = 0;
                     thisFrame.len = tokens.length() - 3;
-                    for (int d = 0; d < thisFrame.len; d++)
+                    for (unsigned int d = 0; d < thisFrame.len; d++)
                     {
                         if (tokens[d + 3] != "")
                         {
@@ -379,7 +379,7 @@ bool FrameFileIO::saveCRTDFile(QString filename, const QVector<CANFrame>* frames
         outFile->write(QString::number(frames->at(c).ID, 16).toUpper().rightJustified(8, '0').toUtf8());
         outFile->putChar(' ');
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write(QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(' ');
@@ -446,9 +446,9 @@ bool FrameFileIO::loadNativeCSVFile(QString filename, QVector<CANFrame>* frames)
                 {
                     thisFrame.isReceived = true;
                     thisFrame.bus = tokens[3].toInt();
-                    thisFrame.len = tokens[4].toInt();
+                    thisFrame.len = tokens[4].toUInt();
                     for (int c = 0; c < 8; c++) thisFrame.data[c] = 0;
-                    for (int d = 0; d < thisFrame.len; d++)
+                    for (unsigned int d = 0; d < thisFrame.len; d++)
                         thisFrame.data[d] = tokens[5 + d].toInt(NULL, 16);
                 }
                 else if (fileVersion == 2)
@@ -456,10 +456,10 @@ bool FrameFileIO::loadNativeCSVFile(QString filename, QVector<CANFrame>* frames)
                     if (tokens[3].at(0) == 'R') thisFrame.isReceived = true;
                     else thisFrame.isReceived = false;
                     thisFrame.bus = tokens[4].toInt();
-                    thisFrame.len = tokens[5].toInt();
-                    if (thisFrame.len + 6 > tokens.length()) thisFrame.len = tokens.length() - 6;
+                    thisFrame.len = tokens[5].toUInt();
+                    if (thisFrame.len + 6 > (unsigned int) tokens.length()) thisFrame.len = tokens.length() - 6;
                     for (int c = 0; c < 8; c++) thisFrame.data[c] = 0;
-                    for (int d = 0; d < thisFrame.len; d++)
+                    for (unsigned int d = 0; d < thisFrame.len; d++)
                         thisFrame.data[d] = tokens[6 + d].toInt(NULL, 16);
                 }
 
@@ -570,7 +570,7 @@ bool FrameFileIO::loadGenericCSVFile(QString filename, QVector<CANFrame>* frames
             QList<QByteArray> dataTok = tokens[1].split(' ');
             thisFrame.len = dataTok.length();
             if (thisFrame.len > 8) thisFrame.len = 8;
-            for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = dataTok[d].toInt(NULL, 16);
+            for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = dataTok[d].toInt(NULL, 16);
 
             frames->append(thisFrame);
         }
@@ -608,7 +608,7 @@ bool FrameFileIO::saveGenericCSVFile(QString filename, const QVector<CANFrame>*
         outFile->write(QString::number(frames->at(c).ID, 16).toUpper().rightJustified(8, '0').toUtf8());
         outFile->putChar(44);
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write(QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(' ');
@@ -696,10 +696,9 @@ bool FrameFileIO::loadLogFile(QString filename, QVector<CANFrame>* frames)
                 if (tokens[4] == "s") thisFrame.extended = false;
                     else thisFrame.extended = true;
                 thisFrame.bus = tokens[2].toInt() - 1;
-                thisFrame.len = tokens[5].toInt();
+                thisFrame.len = tokens[5].toUInt();
                 if (thisFrame.len > 8) thisFrame.len = 8;
-                if (thisFrame.len < 0) thisFrame.len = 0;
-                for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = tokens[d + 6].toInt(NULL, 16);
+                for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = tokens[d + 6].toInt(NULL, 16);
                 frames->append(thisFrame);
             }
             else foundErrors = true;
@@ -759,7 +758,7 @@ bool FrameFileIO::saveLogFile(QString filename, const QVector<CANFrame>* frames)
             else outFile->write(" s ");
         outFile->write(QString::number(frames->at(c).len).toUtf8() + " ");
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write(QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(' ');
@@ -836,7 +835,7 @@ bool FrameFileIO::loadIXXATFile(QString filename, QVector<CANFrame>* frames)
 
                 QStringList dataToks = unQuote(tokens[4]).simplified().split(' ');
                 thisFrame.len = dataToks.length();
-                for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = dataToks[d].toInt(NULL, 16);
+                for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = dataToks[d].toInt(NULL, 16);
                 frames->append(thisFrame);
             }
             else foundErrors = true;
@@ -889,7 +888,7 @@ bool FrameFileIO::saveIXXATFile(QString filename, const QVector<CANFrame>* frame
             else outFile->write(",\"Std\"");
         outFile->write(",\"\",\"");
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write(QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(' ');
@@ -952,7 +951,7 @@ bool FrameFileIO::loadCANDOFile(QString filename, QVector<CANFrame>* frames)
 
         if (thisFrame.len <= 8 && thisFrame.ID <= 0x7FF)
         {
-            for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)data[4 + d];
+            for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)data[4 + d];
             frames->append(thisFrame);
         }
         else foundErrors = true;
@@ -1008,7 +1007,7 @@ bool FrameFileIO::saveCANDOFile(QString filename, const QVector<CANFrame>* frame
             data[1] = (char)(ms & 0xFF);
             data[2] = (char)(id & 0xFF);
             data[3] = (char)((id >> 8) + (thisFrame.len << 4));
-            for (int d = 0; d < thisFrame.len; d++) data[4 + d] = (char)thisFrame.data[d];
+            for (unsigned int d = 0; d < thisFrame.len; d++) data[4 + d] = (char)thisFrame.data[d];
             outFile->write(data);
         }
     }
@@ -1074,11 +1073,10 @@ bool FrameFileIO::loadMicrochipFile(QString filename, QVector<CANFrame>* frames)
                         if (thisFrame.ID <= 0x7FF) thisFrame.extended = false;
                             else thisFrame.extended = true;
                         thisFrame.bus = 0;
-                        thisFrame.len = tokens[3].toInt();
+                        thisFrame.len = tokens[3].toUInt();
                         if (thisFrame.len > 8) thisFrame.len = 8;
-                        if (thisFrame.len < 0) thisFrame.len = 0;
-                        if (thisFrame.len + 4 > tokens.length()) thisFrame.len = tokens.length() - 4;
-                        for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)Utility::ParseStringToNum(tokens[4 + d]);
+                        if (thisFrame.len + 4 > (unsigned int) tokens.length()) thisFrame.len = tokens.length() - 4;
+                        for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)Utility::ParseStringToNum(tokens[4 + d]);
                         frames->append(thisFrame);
                     }
                     else foundErrors = true;
@@ -1140,7 +1138,7 @@ bool FrameFileIO::saveMicrochipFile(QString filename, const QVector<CANFrame>* f
         outFile->write("0x" + QString::number(frames->at(c).ID, 16).toUpper().rightJustified(8, '0').toUtf8() + ";");
         outFile->write(QString::number(frames->at(c).len).toUtf8() + ";");
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write("0x" + QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(';');
@@ -1233,12 +1231,11 @@ bool FrameFileIO::loadTraceFile(QString filename, QVector<CANFrame>* frames)
                     if (thisFrame.ID <= 0x7FF) thisFrame.extended = false;
                         else thisFrame.extended = true;
                     thisFrame.bus = 0;
-                    thisFrame.len = tokens[3].toInt();
-                    if (thisFrame.len < 0) thisFrame.len = 0;
+                    thisFrame.len = tokens[3].toUInt();
                     if (thisFrame.len > 8) thisFrame.len = 8;
                     QList<QByteArray> dataToks = tokens[4].split(' ');
-                    if (thisFrame.len > dataToks.length()) thisFrame.len = dataToks.length();
-                    for (int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)dataToks[d].toInt(NULL, 16);
+                    if (thisFrame.len > (unsigned int) dataToks.length()) thisFrame.len = (unsigned int) dataToks.length();
+                    for (unsigned int d = 0; d < thisFrame.len; d++) thisFrame.data[d] = (unsigned char)dataToks[d].toInt(NULL, 16);
                     frames->append(thisFrame);
                 }
                 else foundErrors = true;
@@ -1325,7 +1322,7 @@ bool FrameFileIO::saveTraceFile(QString filename, const QVector<CANFrame> * fram
 
         outFile->write(QString::number(frames->at(c).len).toUtf8() + "\t");
 
-        for (int temp = 0; temp < frames->at(c).len; temp++)
+        for (unsigned int temp = 0; temp < frames->at(c).len; temp++)
         {
             outFile->write(QString::number(frames->at(c).data[temp], 16).toUpper().rightJustified(2, '0').toUtf8());
             outFile->putChar(' ');
diff --git a/scriptcontainer.cpp b/scriptcontainer.cpp
index 9e14e2d..84b7280 100644
--- a/scriptcontainer.cpp
+++ b/scriptcontainer.cpp
@@ -93,13 +93,12 @@ void ScriptContainer::sendFrame(QJSValue bus, QJSValue id, QJSValue length, QJSV
     CANFrame frame;
     frame.extended = false;
     frame.ID = id.toInt();
-    frame.len = length.toInt();
-    if (frame.len < 0) frame.len = 0;
+    frame.len = length.toUInt();
     if (frame.len > 8) frame.len = 8;
 
     if (!data.isArray()) qDebug() << "data isn't an array";
 
-    for (int i = 0; i < frame.len; i++)
+    for (unsigned int i = 0; i < frame.len; i++)
     {
         frame.data[i] = (uint8_t)data.property(i).toInt();
     }
@@ -125,7 +124,7 @@ void ScriptContainer::gotFrame(const CANFrame &frame)
             QJSValueList args;
             args << frame.bus << frame.ID << frame.len;
             QJSValue dataBytes = scriptEngine.newArray(frame.len);
-            for (int j = 0; j < frame.len; j++) dataBytes.setProperty(j, QJSValue(frame.data[j]));
+            for (unsigned int j = 0; j < frame.len; j++) dataBytes.setProperty(j, QJSValue(frame.data[j]));
             args.append(dataBytes);
             gotFrameFunction.call(args);
             return; //as soon as one filter matches we jump out