This is a platform reference for the source-supported RK3576/RK3506/RV1126B family. On ArmSoM it may be relevant to Sige5, CM5 and AIM5 (RK3576), but that does not establish a board-level CAN FD interface. Confirm schematic, transceiver, pinmux, termination, clock and the released 6.1 BSP. No ArmSoM hardware test was performed.
Source baseline: Rockchip CAN FD Developer Guide, RK-KF-YF-162, V1.3.0, 2025-04-08. Chinese source has 9 pages and English source 11 pages because its revision history occupies a separate page; technical content is aligned. Both contain no independent technical figures. Cover/legal material, intended audience and revision history are omitted. Editorial notes.
1. CAN FD driver
1.1 Driver file and DTS
drivers/net/can/rockchip/rk3576_canfd.c
interrupts = <GIC_SPI 121 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&cru CLK_CAN0>, <&cru HCLK_CAN0>;
clock-names = "baudclk", "apb_pclk";
resets = <&cru SRST_CAN0>, <&cru SRST_H_CAN0>;
reset-names = "can", "can-apb";
&can0 {
assigned-clocks = <&cru CLK_CAN0>;
assigned-clock-rates = <200000000>;
pinctrl-names = "default";
pinctrl-0 = <&can0m0_pins>;
status = "okay";
};
The interrupt follows conversion completion. Clock properties switch clocks and reset properties reset the bus. Configure CAN-H/CAN-L IOMUX for CAN function.
&can0 { rockchip,rx-max-data = <4>; };
&can0 { rockchip,auto-retx-cnt = <100>; };
&can0 {
dmas = <&dmac0 20>;
dma-names = "rx";
};
For classic CAN frames, <4> permits RX byte support of 8 and gives 64 RX FIFO entries. CAN FD frames can use <18> (RX byte support 64) and give 14 FIFO frames. When omitted, TX retries are unlimited; 1 to 0xffff limits retries. RX DMA is optional; remove both DMA properties to disable it.
1.2 Kernel and test tools
+CONFIG_CAN=y
+CONFIG_CANFD_RK3576=y
BR2_PACKAGE_CAN_UTILS=y
BR2_PACKAGE_IPROUTE2=y
canutils contains canconfig, candump, canecho, cansend, and cansequence; use full iproute2, not BusyBox ip.
1.3 Configure, send and receive
ifconfig -a
ip link set can0 down
ip link set can0 type can bitrate 1000000 dbitrate 3000000 fd on
ip -details link show can0
ip link set can0 up
# CAN FD standard and extended data frames
cansend can0 123##1DEADBEEF
cansend can0 00000123##1DEADBEEF
candump can0 &
The first rate is the arbitration segment (1 Mbit/s here); dbitrate is the data segment (3 Mbit/s here).
1.4 Common CAN/CAN FD commands
ip link set can0 down
ip link set can0 type can bitrate 500000 sample-point 0.8 dbitrate 2000000 dsample-point 0.8 fd on
ip -details -statistics link show can0
ip link set can0 up
echo 4096 > /sys/class/net/can0/tx_queue_len
candump can0 &
# Classic CAN: extended, standard, remote-standard, remote-extended
cangen can0 -g 1 -e -I i -L i -D r
cangen can0 -g 1 -I i -L i -D r
cangen can0 -g 1 -R -I i -L i -D r
cangen can0 -g 1 -e -R -I i -L i -D r
# CAN FD without bitrate switching: extended then standard
cangen can0 -g 1 -e -f -I i -L i -D i
cangen can0 -g 1 -e -f -I r -L i -D r
cangen can0 -g 1 -f -I i -L i -D i
cangen can0 -g 1 -f -I r -L i -D r
# CAN FD BRS: extended then standard
cangen can0 -g 1 -e -f -b -I i -L i -D i
cangen can0 -g 1 -e -f -b -I r -L i -D r
cangen can0 -g 1 -f -b -I i -L i -D i
cangen can0 -g 1 -f -b -I r -L i -D r
2. Troubleshooting
2.1 Cannot send or receive
ip link set can0 down
ip link set can0 type can bitrate 500000 sample-point 0.8 dbitrate 2000000 dsample-point 0.8 fd on loopback on
ip -details -statistics link show can0
ip link set can0 up
echo 4096 > /sys/class/net/can0/tx_queue_len
candump can0 &
If loopback allows candump to receive a sent frame, inspect IOMUX, wiring, 120-ohm termination and transceiver. For intermittent failures, use ip -details -statistics link show can0 to verify actual rate and keep sample points consistent throughout the network.
3. Bit rate and sampling point
/* Use CiA recommended sample points */
if (bt->sample_point) {
sample_point_nominal = bt->sample_point;
} else {
if (bt->bitrate > 800000)
sample_point_nominal = 750;
else if (bt->bitrate > 500000)
sample_point_nominal = 800;
else
sample_point_nominal = 875;
}
BitRate = clk_can / (2 *(brq + 1) / ((tseg2 + 1) + (tseg1 + 1) + 1)
Sample = (1 + (tseg1 + 1)) / (1 + (tseg1 + 1) + (tseg2 + 1))
brq, tseg1, and tseg2 are in the target CAN BITTIMING register. Verify all field limits in the matching TRM/BSP.
4. Speed variation and TDC
The source warns that rates above 5 Mbit/s may become unstable. Measure loop delay before configuring TDC:
io -4 0x2ac00108 0x80
cansend 001#aaaaaaaa
io -4 0x2ac00110
The value read from 0x2ac00110 is the loop delay. Then configure TDC:
io -4 0x2ac00108 0x19
Set tdc_offset to half the measured loop delay and enable tdc_enable. Refer to the target TRM CANFD RKCAN_FD_TDC register, then implement the final value in tdc configuration in rk3576_canfd_set_bittiming(). Keep sampling points consistent on a variable-speed CAN FD network or BRS-bit reception can fail.
ip link set can0 type can bitrate 500000 sample-point 0.8 dbitrate 2000000 dsample-point 0.8 fd on