Add an option to control CAN frame padding (on by default).

Fixed #1.

4 files changed, 12 insertions, 4 deletions

diff --git a/src/isotp/isotp.c b/src/isotp/isotp.c
index f115810e..ad693416 100644
--- a/src/isotp/isotp.c
+++ b/src/isotp/isotp.c
@@ -10,7 +10,8 @@ IsoTpShims isotp_init_shims(LogShim log, SendCanMessageShim send_can_message,
     IsoTpShims shims = {
         log: log,
         send_can_message: send_can_message,
-        set_timer: set_timer
+        set_timer: set_timer,
+        frame_padding: ISO_TP_DEFAULT_FRAME_PADDING_STATUS
     };
     return shims;
 }
diff --git a/src/isotp/isotp_types.h b/src/isotp/isotp_types.h
index d9fe4601..5a40733f 100644
--- a/src/isotp/isotp_types.h
+++ b/src/isotp/isotp_types.h
@@ -96,11 +96,20 @@ typedef void (*IsoTpCanFrameSentHandler)(const IsoTpMessage* message);
  * with the wider system.
  *
  * Use the isotp_init_shims(...) function to create an instance of this struct.
+ *
+ * By default, all CAN frames sent from this device in the process of an ISO-TP
+ * message are padded out to a complete 8 byte frame. This is often required by
+ * ECUs. To disable this feature, change the 'frame_padding' field to false on
+ * the IsoTpShims object returned from isotp_init_shims(...).
+ *
+ * frame_padding - true if outgoing CAN frames should be padded to a full 8
+ *      bytes.
  */
 typedef struct {
     LogShim log;
     SendCanMessageShim send_can_message;
     SetTimerShim set_timer;
+    bool frame_padding;
 } IsoTpShims;
 
 /* Private: PCI types, for identifying each frame of an ISO-TP message.
diff --git a/src/isotp/receive.h b/src/isotp/receive.h
index e7e56d61..1dfd6f6d 100644
--- a/src/isotp/receive.h
+++ b/src/isotp/receive.h
@@ -29,8 +29,6 @@ typedef struct {
     IsoTpMessageReceivedHandler message_received_callback;
     uint16_t timeout_ms;
     // timeout_ms: ISO_TP_DEFAULT_RESPONSE_TIMEOUT,
-    bool frame_padding;
-    // frame_padding: ISO_TP_DEFAULT_FRAME_PADDING_STATUS,
     uint8_t* receive_buffer;
     uint16_t received_buffer_size;
     uint16_t incoming_message_size;
diff --git a/src/isotp/send.c b/src/isotp/send.c
index 798fab83..e849bb2c 100644
--- a/src/isotp/send.c
+++ b/src/isotp/send.c
@@ -37,7 +37,7 @@ IsoTpSendHandle isotp_send_single_frame(IsoTpShims* shims, IsoTpMessage* message
     }
 
     shims->send_can_message(message->arbitration_id, can_data,
-            1 + message->size);
+            shims->frame_padding ? 8 : 1 + message->size);
     handle.success = true;
     isotp_complete_send(shims, message, true, callback);
     return handle;