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fix(can): Eliminate persistent CAN RX latency after startup bursts #64

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Merged
qzhhhi merged 1 commit into from
Jul 6, 2026
Merged

fix(can): Eliminate persistent CAN RX latency after startup bursts #64

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75 changes: 39 additions & 36 deletions firmware/c_board/app/src/can/can.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -55,43 +55,46 @@ class Can : private core::utility::Immovable {
}

void handle_uplink(data::DataId field_id, core::protocol::Serializer& serializer) {
auto hal_can_state = hal_can_handle_->State;
auto* hal_can_instance = hal_can_handle_->Instance;

core::utility::assert_always(
(hal_can_state == HAL_CAN_STATE_READY) || (hal_can_state == HAL_CAN_STATE_LISTENING));
core::utility::assert_always((hal_can_instance->RF0R & CAN_RF0R_FMP0) != 0U);

const auto rir = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RIR;
const auto rdtr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDTR;

data::CanDataView data{};
data.is_fdcan = false;
data.is_extended_can_id = static_cast<bool>(CAN_RI0R_IDE & rir);
data.is_remote_transmission = static_cast<bool>(CAN_RI0R_RTR & rir);

if (data.is_extended_can_id) {
data.can_id = ((CAN_RI0R_EXID | CAN_RI0R_STID) & rir) >> CAN_RI0R_EXID_Pos;
} else {
data.can_id = (CAN_RI0R_STID & rir) >> CAN_TI0R_STID_Pos;
while ((hal_can_handle_->Instance->RF0R & CAN_RF0R_FMP0) != 0U) {
auto hal_can_state = hal_can_handle_->State;
auto* hal_can_instance = hal_can_handle_->Instance;

core::utility::assert_always(
(hal_can_state == HAL_CAN_STATE_READY)
|| (hal_can_state == HAL_CAN_STATE_LISTENING));
core::utility::assert_always((hal_can_instance->RF0R & CAN_RF0R_FMP0) != 0U);

const auto rir = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RIR;
const auto rdtr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDTR;

data::CanDataView data{};
data.is_fdcan = false;
data.is_extended_can_id = static_cast<bool>(CAN_RI0R_IDE & rir);
data.is_remote_transmission = static_cast<bool>(CAN_RI0R_RTR & rir);

if (data.is_extended_can_id) {
data.can_id = ((CAN_RI0R_EXID | CAN_RI0R_STID) & rir) >> CAN_RI0R_EXID_Pos;
} else {
data.can_id = (CAN_RI0R_STID & rir) >> CAN_TI0R_STID_Pos;
}

size_t can_data_length = (CAN_RDT0R_DLC & rdtr) >> CAN_RDT0R_DLC_Pos;
if (data.is_remote_transmission)
can_data_length = 0;

alignas(uint32_t) std::array<std::byte, 8> can_data{};
const uint32_t rdlr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDLR;
const uint32_t rdhr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDHR;
std::memcpy(can_data.data(), &rdlr, sizeof(uint32_t));
std::memcpy(can_data.data() + 4, &rdhr, sizeof(uint32_t));
data.can_data = {can_data.data(), can_data_length};

core::utility::assert_always(
serializer.write_can(field_id, data)
!= core::protocol::Serializer::SerializeResult::kInvalidArgument);

hal_can_instance->RF0R |= CAN_RF0R_RFOM0;
}

size_t can_data_length = (CAN_RDT0R_DLC & rdtr) >> CAN_RDT0R_DLC_Pos;
if (data.is_remote_transmission)
can_data_length = 0;

alignas(uint32_t) std::array<std::byte, 8> can_data{};
const uint32_t rdlr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDLR;
const uint32_t rdhr = hal_can_instance->sFIFOMailBox[CAN_RX_FIFO0].RDHR;
std::memcpy(can_data.data(), &rdlr, sizeof(uint32_t));
std::memcpy(can_data.data() + 4, &rdhr, sizeof(uint32_t));
data.can_data = {can_data.data(), can_data_length};

core::utility::assert_always(
serializer.write_can(field_id, data)
!= core::protocol::Serializer::SerializeResult::kInvalidArgument);

hal_can_instance->RF0R |= CAN_RF0R_RFOM0;
}

bool try_transmit() {
Expand Down
47 changes: 30 additions & 17 deletions firmware/rmcs_board/app/src/can/can.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -86,20 +86,25 @@ class Can : private core::utility::Immovable {
}

void handle_uplink(core::protocol::FieldId field_id, core::protocol::Serializer& serializer) {
mcan_rx_message_t rx;
core::utility::assert_always(mcan_read_rxfifo(can_base_, 0, &rx) == status_success);

data::CanDataView data;
const size_t data_length = rx.dlc;
data.is_fdcan = false;
data.is_extended_can_id = rx.use_ext_id;
data.is_remote_transmission = rx.rtr;
data.can_id = data.is_extended_can_id ? rx.ext_id : rx.std_id;
data.can_data = {reinterpret_cast<const std::byte*>(rx.data_8), data_length};

core::utility::assert_always(
serializer.write_can(field_id, data)
!= core::protocol::Serializer::SerializeResult::kInvalidArgument);
while (true) {
mcan_rx_message_t rx;
const hpm_stat_t status = mcan_read_rxfifo(can_base_, 0, &rx);
if (status == status_mcan_rxfifo_empty)
return;
core::utility::assert_always(status == status_success);

data::CanDataView data;
const size_t data_length = rx.dlc;
data.is_fdcan = false;
data.is_extended_can_id = rx.use_ext_id;
data.is_remote_transmission = rx.rtr;
data.can_id = data.is_extended_can_id ? rx.ext_id : rx.std_id;
data.can_data = {reinterpret_cast<const std::byte*>(rx.data_8), data_length};

core::utility::assert_always(
serializer.write_can(field_id, data)
!= core::protocol::Serializer::SerializeResult::kInvalidArgument);
}
}

void irq_handler() {
Expand All @@ -108,10 +113,18 @@ class Can : private core::utility::Immovable {
if (!flags) [[unlikely]]
return;

if (flags & MCAN_INT_RXFIFO0_NEW_MSG) [[likely]]
handle_uplink(data_id_, usb::get_serializer());
uint32_t remaining_flags = flags;
if (flags & MCAN_INT_RXFIFO0_NEW_MSG) [[likely]] {
mcan_clear_interrupt_flags(can_base_, MCAN_INT_RXFIFO0_NEW_MSG);

auto& serializer = usb::get_serializer();
handle_uplink(data_id_, serializer);

remaining_flags &= ~MCAN_INT_RXFIFO0_NEW_MSG;
}

mcan_clear_interrupt_flags(can_base_, flags);
if (remaining_flags != 0U)
mcan_clear_interrupt_flags(can_base_, remaining_flags);
}

private:
Expand Down
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