diff --git a/extensions/openpower-pels/ascii_string.cpp b/extensions/openpower-pels/ascii_string.cpp
new file mode 100644
index 0000000..6d4711e
--- /dev/null
+++ b/extensions/openpower-pels/ascii_string.cpp
@@ -0,0 +1,83 @@
+#include "ascii_string.hpp"
+
+#include "pel_types.hpp"
+
+#include <phosphor-logging/log.hpp>
+
+namespace openpower
+{
+namespace pels
+{
+namespace src
+{
+
+using namespace phosphor::logging;
+
+AsciiString::AsciiString(Stream& stream)
+{
+    unflatten(stream);
+}
+
+AsciiString::AsciiString(const message::Entry& entry)
+{
+    // Power Error:  1100RRRR
+    // BMC Error:    BDSSRRRR
+    // where:
+    //  RRRR = reason code
+    //  SS = subsystem ID
+
+    // First is type, like 'BD'
+    setByte(0, entry.src.type);
+
+    // Next is '00', or subsystem ID
+    if (entry.src.type == static_cast<uint8_t>(SRCType::powerError))
+    {
+        setByte(2, 0x00);
+    }
+    else // BMC Error
+    {
+        setByte(2, entry.subsystem);
+    }
+
+    // Then the reason code
+    setByte(4, entry.src.reasonCode >> 8);
+    setByte(6, entry.src.reasonCode & 0xFF);
+
+    // Padded with spaces
+    for (size_t offset = 8; offset < asciiStringSize; offset++)
+    {
+        _string[offset] = ' ';
+    }
+}
+
+void AsciiString::flatten(Stream& stream)
+{
+    stream.write(_string.data(), _string.size());
+}
+
+void AsciiString::unflatten(Stream& stream)
+{
+    stream.read(_string.data(), _string.size());
+}
+
+std::string AsciiString::get() const
+{
+    std::string string{_string.begin(), _string.begin() + _string.size()};
+    return string;
+}
+
+void AsciiString::setByte(size_t byteOffset, uint8_t value)
+{
+    assert(byteOffset < asciiStringSize);
+
+    char characters[3];
+    sprintf(characters, "%02X", value);
+
+    auto writeOffset = byteOffset;
+    _string[writeOffset++] = characters[0];
+    _string[writeOffset] = characters[1];
+}
+
+} // namespace src
+} // namespace pels
+} // namespace openpower