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CAN/CAN FD Performance Test

Test Environment​

  • STM32H750VB @ 480MHz
  • FDCAN1 connected to FDCAN2
  • FDCAN1/FDCAN2 directly forward received frames in callback
  • Count number of received CAN packets per second in ISR
  • Arbitration phase set to 1Mbps, FD data phase set to 2.5Mbps

Test Code​

STDIO::write_ = uart_cdc.write_port_;
constexpr uint32_t PACK_ID = 0x123;
constexpr CAN::Type PACK_TYPE = CAN::Type::STANDARD;
constexpr uint32_t PACK_NUM = 8;

static volatile uint32_t counter = 0, speed = 0;

void (*can_func)(bool, LibXR::STM32CANFD *, const CAN::ClassicPack &) =
    [](bool, LibXR::STM32CANFD *can, const CAN::ClassicPack &pack)
{
  can->AddMessage(pack);
  counter++;
};

auto cb_can1 = CAN::Callback::Create(can_func, &fdcan1);
fdcan1.Register(cb_can1, PACK_TYPE);
auto cb_can2 = CAN::Callback::Create(can_func, &fdcan2);
fdcan2.Register(cb_can2, PACK_TYPE);

LibXR::CAN::ClassicPack pack;
pack.id = PACK_ID;
pack.type = PACK_TYPE;
pack.dlc = 8;

for (uint32_t i = 0; i < PACK_NUM; i++)
{
  fdcan1.AddMessage(pack);
}

while (true)
{
  Thread::Sleep(1000);
  speed = counter;
  counter = 0;
  XR_LOG_DEBUG("speed: %u", speed);
}
Code block collapsed

Test Results​

Bus load is computed from the frame bits plus a 3-bit interframe space, without bit stuffing.

Standard Frame (8-byte data)​

8917 packets/s, 108 bits per frame, data segment rate1 = 0.57 Mbps, bus load ≈ 100%

Upper bound without bit stuffing: 64 / (108 + 3) × 1 Mbps ≈ 0.577 Mbps

Extended Frame (8-byte data)​

7401 packets/s, 128 bits per frame, data segment rate = 0.47 Mbps, bus load ≈ 100%

Standard Remote Frame​

20357 packets/s, 44 bits per frame, bus load ≈ 100%

Extended Remote Frame​

14054 packets/s, 64 bits per frame, bus load ≈ 100%

FD Standard Frame (64-byte data)​

3929 packets/s, data segment rate1 = 2.01 Mbps, bus load ≈ 100%

FD Extended Frame (64-byte data)​

3617 packets/s, data segment rate1 = 1.85 Mbps, bus load ≈ 100%

Summary​

On STM32H750 (480 MHz), with FDCAN1 and FDCAN2 connected on the board and each receive callback forwarding the frame, both classic and FD frames keep the bus load close to 100%.

Footnotes​

  1. Here, “data segment rate” means effective payload throughput, calculated as packets/s × payload bytes per packet × 8. It is not the physical CAN FD data-phase bit rate configured in the controller; according to the test conditions above, the physical FD data-phase bit rate is 2.5 Mbps. ↩ ↩2 ↩3