From c39ec1581e3fbc59de7f882adf2e6fbb574fb42e Mon Sep 17 00:00:00 2001
From: Jeff Epler <jepler@gmail.com>
Date: Fri, 18 Sep 2020 11:14:59 -0500
Subject: [PATCH] _canio: Message: setting data clears rtr, and vice versa

---
 shared-bindings/_canio/Message.c | 4 ++--
 shared-module/_canio/Message.c   | 4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/shared-bindings/_canio/Message.c b/shared-bindings/_canio/Message.c
index 85657e05ef..c7ef5d4582 100644
--- a/shared-bindings/_canio/Message.c
+++ b/shared-bindings/_canio/Message.c
@@ -117,7 +117,7 @@ STATIC const mp_obj_property_t canio_message_id_obj = {
 //|     data: bytes
 //|     """The content of the message, or dummy content in the case of an rtr.
 //|
-//|     Assigning to data also sets the length."""
+//|     Assigning to data also sets the length and clears the rtr flag."""
 //|
 STATIC mp_obj_t canio_message_data_get(const mp_obj_t self_in) {
     canio_message_obj_t *self = self_in;
@@ -202,7 +202,7 @@ STATIC const mp_obj_property_t canio_message_extended_obj = {
 
 
 //|     rtr: bool
-//|     """True if the message represents a remote transmission request (RTR)"""
+//|     """True if the message represents a remote transmission request (RTR).  Setting rtr to true zeros out data"""
 //|
 STATIC mp_obj_t canio_message_rtr_get(const mp_obj_t self_in) {
     canio_message_obj_t *self = self_in;
diff --git a/shared-module/_canio/Message.c b/shared-module/_canio/Message.c
index 0caca58f02..a02bd01276 100644
--- a/shared-module/_canio/Message.c
+++ b/shared-module/_canio/Message.c
@@ -59,6 +59,7 @@ const void *common_hal_canio_message_get_data(const canio_message_obj_t *self)
 
 const void common_hal_canio_message_set_data(canio_message_obj_t *self, const void *data, size_t size)
 {
+    self->rtr = false;
     self->size = size;
     memcpy(self->data, data, size);
 }
@@ -84,6 +85,9 @@ bool common_hal_canio_message_get_rtr(const canio_message_obj_t *self)
 void common_hal_canio_message_set_rtr(canio_message_obj_t *self, bool rtr)
 {
     self->rtr = rtr;
+    if (rtr) {
+        memset(self->data, 0, self->size);
+    }
 }
 
 bool common_hal_canio_message_get_extended(const canio_message_obj_t *self)