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AM335X CAN 速度小于10k，无法发送数据

user4796556
Expert 1352 points


hi:

我使用的SDK是sdk-processor-03.02,使用了CAN0和CAN1，在dts文件中启用后，在linux下面，使用

root@am335x-evm:~# canconfig can1 bitrate 20000 ctrlmode triple-sampling on
can1 bitrate: 20000, sample-point: 0.875
can1 ctrlmode: loopback[OFF], listen-only[OFF], tripple-sampling[ON],one-shot[OFF], berr-reporting[OFF]
root@am335x-evm:~# canconfig can0 bitrate 20000 ctrlmode triple-sampling on
can0 bitrate: 20000, sample-point: 0.875
can0 ctrlmode: loopback[OFF], listen-only[OFF], tripple-sampling[ON],one-shot[OFF], berr-reporting[OFF]
root@am335x-evm:~# canconfig can0 start
[ 50.903121] c_can_platform 481cc000.can can0: setting BTR=1c3b BRPE=0000
can0 state: ERROR-ACTIVE
root@am335x-evm:~# canconfig can1 start
[ 56.105140] c_can_platform 481d0000.can can1: setting BTR=1c3b BRPE=0000
can1 state: ERROR-ACTIVE

root@am335x-evm:~# cansend can0 -i 0x10 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
interface = can0, family = 29, type = 3, proto = 1
root@am335x-evm:~# cansend can0 -i 0x10 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
interface = can0, family = 29, type = 3, proto = 1

root@am335x-evm:~# candump can1
interface = can1, family = 29, type = 3, proto = 1
<0x010> [8] 11 22 33 44 55 66 77 88
<0x010> [8] 11 22 33 44 55 66 77 88
^C
root@am335x-evm:~# candump can0
interface = can0, family = 29, type = 3, proto = 1
<0x010> [8] 11 22 33 44 55 66 77 88

在速度为20K的情况下可以正常接收数据。

以下是10k的配置，没有数据，示波器测试也没有波形。

root@am335x-evm:~# canconfig can0 bitrate 10000 ctrlmode triple-sampling on
can0 bitrate: 10000, sample-point: 0.875
can0 ctrlmode: loopback[OFF], listen-only[OFF], tripple-sampling[ON],one-shot[OFF], berr-reporting[OFF]
root@am335x-evm:~# canconfig can1 bitrate 10000 ctrlmode triple-sampling on
can1 bitrate: 10000, sample-point: 0.875
can1 ctrlmode: loopback[OFF], listen-only[OFF], tripple-sampling[ON],one-shot[OFF], berr-reporting[OFF]
root@am335x-evm:~# canconfig can0 start
[ 909.184909] c_can_platform 481cc000.can can0: setting BTR=1c37 BRPE=0001
can0 state: ERROR-ACTIVE
root@am335x-evm:~# canconfig can1 start
[ 913.222162] c_can_platform 481d0000.can can1: setting BTR=1c37 BRPE=0001
can1 state: ERROR-ACTIVE
root@am335x-evm:~# cansend can0 -i 0x10 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
interface = can0, family = 29, type = 3, proto = 1
root@am335x-evm:~# cansend can0 -i 0x10 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
interface = can0, family = 29, type = 3, proto = 1
root@am335x-evm:~# cansend can0 -i 0x10 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
interface = can0, family = 29, type = 3, proto = 1

使用candump命令，没有任何数据，请教是怎么回事？

  • 0
    TI__Mastermind 19320 points

    看一下代码，会不会是速率太低了 PLL参数无法配置成功？

  • 0 回复 Denny%20Yang99373
    Expert 1352 points

    Denny 你好：

        我看了下代码，添加了一些 调试信息，然后启动后用devmem2读取了BTR的寄存器，调试信息中没有提示有速度设置错误，BTR寄存器的值和设置的也是一样的，我想请教下您指的PLL参数无法配置成功是什么意思，PLL参数在哪里配置的？还有我用的是SDK-PROCESSOR-03.02版本的，这个版本的CAN是否支持10K以下的速度？

       PS:loopback测试正常，但是示波器无法测量到波形。

  • 0 回复 Denny%20Yang99373
    Expert 1352 points

    denny你好：

         之前的回复好像没发出来，请问您说的PLL参数无法配置成功是什么意思？AM335X不支持10K以下的速度吗？如果我想用到10K以下的速度该如何修改？

    10K的速度，我调试了下驱动，关于寄存器的配置没有问题，用devmem2读取出来的寄存器数和驱动中写入的值是一样的。为什么就不能工作呢？10k的速度，loopback成功，但是示波器测量不到数据

  • 0 回复 user4796556
    TI__Mastermind 45260 points

    请参考下这个帖子，问题类似：

    http://www.deyisupport.com/question_answer/dsp_arm/sitara_arm/f/25/t/126338.aspx

    看起来应该是can transiver的限制。