Spidev test question

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
1

Hi, I’m using devkit board Xavier NX to test its spi pin using R35.3.1. And after I enabled spi1 and spi3, it is ok in spi1 using spidev_test tool as follows (connect pin19 and pin21):

nvidia@nvidia:~/test$ sudo ./spidev_test -D /dev/spidev0.0 -v -p hello
spi mode: 0x0
bits per word: 8
max speed: 50000000 Hz (50000 kHz)
TX | 68 65 6C 6C 6F __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |hello|
RX | 68 65 6C 6C 6F __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |hello|

But when I connect spi3 MISO and MOSI (pin22 and pin37), it can not get the right data as below:

nvidia@nvidia:~/test$ sudo ./spidev_test -D /dev/spidev2.0 -v -p hello
spi mode: 0x0
bits per word: 8
max speed: 50000000 Hz (50000 kHz)
TX | 68 65 6C 6C 6F __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |hello|
RX | 20 20 24 24 27 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |  $$'|

Do you know what causes it?
Thanks

3

Hi 854053437,

Have you used Jetson-IO to enable both spi1(19,21,23,24,26) and spi3(13,16,18,22,37)?

Please share the result of the following command on your board.

$ sudo busybox devmem 0x0243d048 //SPI3_SCK
$ sudo busybox devmem 0x0243d060 //SPI3_MOSI
$ sudo busybox devmem 0x0243d008 //SPI3_MISO
$ sudo busybox devmem 0x0243d018 //SPI3_CS0
$ sudo busybox devmem 0x0243d028 //SPI3_CS1
4

YES, I’ve done that and spi1 works fine.

here is the result

nvidia@nvidia:~/test$ sudo busybox devmem 0x0243d048
0x00001444
nvidia@nvidia:~/test$ sudo busybox devmem 0x0243d060
0x00001444
nvidia@nvidia:~/test$ sudo busybox devmem 0x0243d008
0x00001444
nvidia@nvidia:~/test$ sudo busybox devmem 0x0243d018
0x00001448
nvidia@nvidia:~/test$
nvidia@nvidia:~/test$ sudo busybox devmem 0x0243d028
0x00001448
nvidia@nvidia:~/test$
5

You pinmux seems correct for SPI3.
I could not reproduce your issue on Xavier NX devkit with R35.3.1.

nvidia@nvidia-desktop:~$ sudo ./spidev_test -D /dev/spidev2.0 -v -p hello
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 KHz)
TX | 68 65 6C 6C 6F __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  | hello
RX | 68 65 6C 6C 6F __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  | hello

Do you modify the frequency for SPI interface?

6

Yes, I see its default frequency in dtb is 50000000, so I change it in spidev_test.c

7

Hello, Kevin. I reduced the spi frequency in spidev_test.c and both SPI interface works fine.
It seems due to the frequency, thank you for help!

But I still wonder why SPI1 works fine while SPI3 don’t in the same high frequency.

8

It may relate to the default clock used for SPI3.
The clock frequency for SPI3 is lower than SPI1 by default.

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10

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