From 6d8cfb8f30a273cda93ba150407e364839b3fa34 Mon Sep 17 00:00:00 2001
From: "David J. Fiddes" <D.J@fiddes.net>
Date: Thu, 2 Oct 2025 19:06:19 +0100
Subject: [PATCH] Fix CAN SDO print timeout

The class needs to be properly initialised as
the TriggerTimeout() method will likely be
called before any incoming SDO frames. On
the VCU I observed unitialised member
variables being filled with garbage from the
stack painting.

The previous TriggerTimeout() logic causes
timeouts even when no timeout period has
elapsed. This corrupts the parameter
database download. Overshooting and setting
to zero if required seems to work reliably. I
don't understand.

Tests:
 - Repeatedly start a db download, abort and
   immediate retry. This should fail and it does.
  - Repeatedly start a db download, abort and
    wait a few seconds to retry. This should
    succeed and it does.
  - Use callingFrequency values of 97 and 103
    to force over and undershoots. Verify the
    timeout behaviour works as expected.
---
 src/cansdo.cpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/cansdo.cpp b/src/cansdo.cpp
index df3846d..c00ca82 100644
--- a/src/cansdo.cpp
+++ b/src/cansdo.cpp
@@ -41,7 +41,10 @@
  *
  */
 CanSdo::CanSdo(CanHardware* hw, CanMap* cm)
- : canHardware(hw), canMap(cm), nodeId(1), remoteNodeId(255), printRequest(-1)
+ : canHardware(hw), canMap(cm), nodeId(1), remoteNodeId(255), printRequest(-1),
+   printByteIn(0), printByteOut(sizeof(printBuffer)), printTimeout(PRINT_TIMEOUT),
+   mapParam(Param::PARAM_INVALID), mapId(0), sdoReplyValid(false), sdoReplyData(0),
+   pendingUserSpaceSdo(false)
 {
    canHardware->AddCallback(this);
    HandleClear();
@@ -213,11 +216,14 @@ void CanSdo::ProcessSDO(uint32_t data[2])
  */
 void CanSdo::TriggerTimeout(int callingFrequency)
 {
-   if (printTimeout == 0) return;
-   if (callingFrequency >= printTimeout)
+   if (printTimeout > 0)
+   {
       printTimeout -= callingFrequency;
-   else
+   }
+   if (printTimeout < 0)
+   {
       printTimeout = 0;
+   }
 }
 
 void CanSdo::PutChar(char c)