From 84593d61ebd141983f2083dfef3dc52960c83c0a Mon Sep 17 00:00:00 2001
From: Balazs Racz <balazs.racz@gmail.com>
Date: Sat, 5 Aug 2023 21:24:34 +0200
Subject: [PATCH 1/2] Cancel messages in the queue when we are in error passive
mode.
---
src/freertos_drivers/st/Stm32Can.cxx | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/src/freertos_drivers/st/Stm32Can.cxx b/src/freertos_drivers/st/Stm32Can.cxx
index eb20fc2dc..b08d65ea6 100644
--- a/src/freertos_drivers/st/Stm32Can.cxx
+++ b/src/freertos_drivers/st/Stm32Can.cxx
@@ -219,6 +219,19 @@ void Stm32Can::disable()
*/
void Stm32Can::tx_msg()
{
+ // If we are error passive, the last transmission ended with an error, and
+ // there are no free TX mailboxes, then we flush the input queue. This is a
+ // workaround because the STM32 CAN controller can get stuck in this state
+ // and never get to bus off if the TX attempts end up with no-ack (meaning
+ // the controller is alone on the bus).
+ if ((CAN->ESR & CAN_ESR_EPVF) && ((CAN->ESR & CAN_ESR_LEC_Msk) != 0) &&
+ ((CAN->TSR & (CAN_TSR_TME0 | CAN_TSR_TME1 | CAN_TSR_TME2)) == 0))
+ {
+ txBuf->flush();
+ txBuf->signal_condition();
+ return;
+ }
+
/* see if we can send anything out */
struct can_frame *can_frame;
From ed2cdc468f84a551b32e790ca95f38003ad297cb Mon Sep 17 00:00:00 2001
From: Balazs Racz <balazs.racz@gmail.com>
Date: Sat, 5 Aug 2023 21:29:16 +0200
Subject: [PATCH 2/2] Cancels the transmit queue for both error passive and bus
off states. Removes flag clear statements for error flags in the ESR
register, because these flags are not writeable (can not be cleared in
software).
---
src/freertos_drivers/st/Stm32Can.cxx | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/src/freertos_drivers/st/Stm32Can.cxx b/src/freertos_drivers/st/Stm32Can.cxx
index b08d65ea6..003c9e054 100644
--- a/src/freertos_drivers/st/Stm32Can.cxx
+++ b/src/freertos_drivers/st/Stm32Can.cxx
@@ -448,31 +448,35 @@ void Stm32Can::sce_interrupt_handler()
/* error interrupt has occured */
CAN->MSR |= CAN_MSR_ERRI; // clear flag
+ bool cancel_queue = false;
+
if (CAN->ESR & CAN_ESR_EWGF)
{
/* error warning condition */
state_ = CAN_STATE_BUS_WARNING;
- CAN->ESR &= ~CAN_ESR_EWGF;
}
if (CAN->ESR & CAN_ESR_EPVF)
{
/* error passive condition */
++softErrorCount;
state_ = CAN_STATE_BUS_PASSIVE;
- CAN->ESR &= ~CAN_ESR_EPVF;
+ cancel_queue = true;
}
if (CAN->ESR & CAN_ESR_BOFF)
{
/* bus off error condition */
+ ++busOffCount;
+ state_ = CAN_STATE_BUS_OFF;
+ cancel_queue = true;
+ }
+ if (cancel_queue)
+ {
CAN->TSR |= CAN_TSR_ABRQ2;
CAN->TSR |= CAN_TSR_ABRQ1;
CAN->TSR |= CAN_TSR_ABRQ0;
CAN->IER &= ~CAN_IER_TMEIE;
txBuf->flush();
txBuf->signal_condition_from_isr();
- ++busOffCount;
- state_ = CAN_STATE_BUS_OFF;
- CAN->ESR &= ~CAN_ESR_BOFF;
}
}
}