diff --git a/RSMS1AMessageBuilder.cpp b/RSMS1AMessageBuilder.cpp
index 8d46f9b..e7d3d34 100644
--- a/RSMS1AMessageBuilder.cpp
+++ b/RSMS1AMessageBuilder.cpp
@@ -21,7 +21,7 @@
 #include "RSMS1AMessageBuilder.h"
 #include "StringUtils.h"
 
-std::vector<char> CRSMS1AMessageBuilder::m_charsToEscape = {-17, 0, 17, 19, -2, -25, 26, -3, -1, 36, 13, 44};
+std::vector<signed char> CRSMS1AMessageBuilder::m_charsToEscape = {-17, 0, 17, 19, -2, -25, 26, -3, -1, 36, 13, 44};
 
 void CRSMS1AMessageBuilder::buildMessage(std::string& message, const std::string& sender, const std::string& recipient, const std::string body)
 {
@@ -30,28 +30,28 @@ void CRSMS1AMessageBuilder::buildMessage(std::string& message, const std::string
     escapeBody(bodyTmp, body + (char)bodyCrc);
     
     std::string header = CStringUtils::string_format("%s,%s,0011", sender.c_str(), recipient.c_str());
-    char c1, c2;
+    signed char c1, c2;
     calcMsgIcomCRC(header, c1, c2);
     header.push_back(c1);
     header.push_back(c2);
     message = "$$Msg," + header + bodyTmp + '\r';
 }   
 
-char CRSMS1AMessageBuilder::calculateBodyCRC(const std::string& body)
+signed char CRSMS1AMessageBuilder::calculateBodyCRC(const std::string& body)
 {
     if(body.length() == 1)
         return body[0];
 
-    unsigned int num = 0;
-    for(auto c : body) {
+    signed int num = 0;
+    for(signed char c : body) {
         num += c;
     }
 
-    auto res = (num & 255);
+    signed int res = (num & 255);
     if(res >= 128)
         res -= 128;
     
-    return (char)res;
+    return (signed char)res;
 }
 
 void CRSMS1AMessageBuilder::escapeBody(std::string& output, const std::string& body)
@@ -65,18 +65,18 @@ void CRSMS1AMessageBuilder::escapeBody(std::string& output, const std::string& b
     }
 }
 
-void CRSMS1AMessageBuilder::calcMsgIcomCRC(const std::string& msg, char& c1, char& c2)
+void CRSMS1AMessageBuilder::calcMsgIcomCRC(const std::string& msg, signed char& c1, signed char& c2)
 {
 	int num = 0;
 	for(unsigned int i = 0U; i < msg.length(); i++) {
 		num += msg[i];
 	}
 
-	c1 = doWhatever((char)((num >> 4) & 15));
-	c2 = doWhatever((char)(num & 15));
+	c1 = doWhatever((signed char)((num >> 4) & 15));
+	c2 = doWhatever((signed char)(num & 15));
 }
 
-char CRSMS1AMessageBuilder::doWhatever(char b2) {
+signed char CRSMS1AMessageBuilder::doWhatever(signed char b2) {
     int i;
     int i2 = b2 & 255;
     if (i2 >= 0 && i2 <= 9) {
@@ -86,7 +86,7 @@ char CRSMS1AMessageBuilder::doWhatever(char b2) {
     } else {
         i = b2 + 55;
     }
-    return (char) i;
+    return (signed char) i;
 }
 
 RSMS1A_PARSE_STATUS CRSMS1AMessageBuilder::parseMessage(std::string& sender, std::string& recipient, std::string& body, const std::string& message)
diff --git a/RSMS1AMessageBuilder.h b/RSMS1AMessageBuilder.h
index 2b13d4b..142c0e2 100644
--- a/RSMS1AMessageBuilder.h
+++ b/RSMS1AMessageBuilder.h
@@ -34,12 +34,12 @@ public:
     static RSMS1A_PARSE_STATUS parseMessage(std::string& sender, std::string& recipient, std::string& body, const std::string& message);
 
 private:
-    static void calcMsgIcomCRC(const std::string& msg, char& c1, char& c2);
+    static void calcMsgIcomCRC(const std::string& msg, signed char& c1, signed char& c2);
     static void escapeBody(std::string& output, const std::string& body);
     static void unescapeBody(std::string& output, const std::string& body);
     static void escapeBytes(std::vector<char> output, const std::vector<char> input);
-    static char calculateBodyCRC(const std::string& body);
-    static char doWhatever(char b2);
+    static signed char calculateBodyCRC(const std::string& body);
+    static signed char doWhatever(signed char b2);
 
-    static std::vector<char> m_charsToEscape;
+    static std::vector<signed char> m_charsToEscape;
 };
\ No newline at end of file
diff --git a/Tests/Utils/swap_endian_be.cpp b/Tests/Utils/swap_endian_be.cpp
index 7099a0e..8e3a817 100644
--- a/Tests/Utils/swap_endian_be.cpp
+++ b/Tests/Utils/swap_endian_be.cpp
@@ -19,6 +19,8 @@
 #include <gtest/gtest.h>
 
 #include "../../Utils.h"
+#include "../../StringUtils.h"
+#include "../../Log.h"
 
 class Utils_swap_endian_be : public ::testing::Test {
  
@@ -31,4 +33,13 @@ TEST_F(Utils_swap_endian_be, SwapUINT32_be) {
     uint32_t res = CUtils::swap_endian_be(test);
 
     EXPECT_EQ(res, 0x12345678U);
-}
\ No newline at end of file
+}
+
+
+TEST_F(Utils_swap_endian_be, blabla) {
+    std::vector<char> charsToEscape = {-17, 0, 17, 19, 128-2, -25, 26, 128-3, -1, 36, 13, 44};
+
+    for(unsigned int i = 1U; i < charsToEscape.size(); i++) {
+        CLog::logDebug("%08x - %08x", charsToEscape[i], (unsigned char)charsToEscape[i]);
+    }
+}