diff --git a/libraries/AP_CANManager/AP_CANManager.cpp b/libraries/AP_CANManager/AP_CANManager.cpp
index 878a67d07f..bbd078bea3 100644
--- a/libraries/AP_CANManager/AP_CANManager.cpp
+++ b/libraries/AP_CANManager/AP_CANManager.cpp
@@ -39,6 +39,8 @@
 #include <AP_HAL_ChibiOS/CANIface.h>
 #endif
 
+#include <AP_Common/ExpandingString.h>
+
 #define LOG_TAG "CANMGR"
 #define LOG_BUFFER_SIZE 1024
 
@@ -373,15 +375,13 @@ void AP_CANManager::log_text(AP_CANManager::LogLevel loglevel, const char *tag,
 }
 
 // log retrieve method used by file sys method to report can log
-uint32_t AP_CANManager::log_retrieve(char* data, uint32_t max_size) const
+void AP_CANManager::log_retrieve(ExpandingString &str) const
 {
     if (_log_buf == nullptr) {
         gcs().send_text(MAV_SEVERITY_ERROR, "Log buffer not available");
-        return 0;
+        return;
     }
-    uint32_t read_len = MIN(max_size, _log_pos);
-    memcpy(data, _log_buf, read_len);
-    return read_len;
+    str.append(_log_buf, _log_pos);
 }
 
 AP_CANManager& AP::can()
diff --git a/libraries/AP_CANManager/AP_CANManager.h b/libraries/AP_CANManager/AP_CANManager.h
index 994536d065..ad0ea040c4 100644
--- a/libraries/AP_CANManager/AP_CANManager.h
+++ b/libraries/AP_CANManager/AP_CANManager.h
@@ -90,7 +90,7 @@ public:
     // Method to log status and debug information for review while debugging
     void log_text(AP_CANManager::LogLevel loglevel, const char *tag, const char *fmt, ...);
 
-    uint32_t log_retrieve(char* data, uint32_t max_size) const;
+    void log_retrieve(ExpandingString &str) const;
 
     // return driver type index i
     Driver_Type get_driver_type(uint8_t i) const
diff --git a/libraries/AP_CANManager/AP_SLCANIface.cpp b/libraries/AP_CANManager/AP_SLCANIface.cpp
index 08801fd7ce..785b7a7ff7 100644
--- a/libraries/AP_CANManager/AP_SLCANIface.cpp
+++ b/libraries/AP_CANManager/AP_SLCANIface.cpp
@@ -536,13 +536,12 @@ uint32_t SLCAN::CANIface::getErrorCount() const
     return 0;
 }
 
-uint32_t SLCAN::CANIface::get_stats(char* data, uint32_t max_size)
+void SLCAN::CANIface::get_stats(ExpandingString &str)
 {
     // When in passthrough mode methods is handled through can iface
     if (_can_iface) {
-        return _can_iface->get_stats(data, max_size);
+        _can_iface->get_stats(str);
     }
-    return 0;
 }
 
 bool SLCAN::CANIface::is_busoff() const
diff --git a/libraries/AP_CANManager/AP_SLCANIface.h b/libraries/AP_CANManager/AP_SLCANIface.h
index 4f12bb6569..d10266b49b 100644
--- a/libraries/AP_CANManager/AP_SLCANIface.h
+++ b/libraries/AP_CANManager/AP_SLCANIface.h
@@ -112,7 +112,7 @@ public:
     bool set_event_handle(AP_HAL::EventHandle* evt_handle) override;
     uint16_t getNumFilters() const override;
     uint32_t getErrorCount() const override;
-    uint32_t get_stats(char* data, uint32_t max_size) override;
+    void get_stats(ExpandingString &) override;
     bool is_busoff() const override;
     bool configureFilters(const CanFilterConfig* filter_configs, uint16_t num_configs) override;
     void flush_tx() override;