ADC using SPI on Xavier

bump5236 · July 9, 2019, 11:07am

Hi guys,
I connected the ADC (MCP3208) to the Expansion Header (SPI1_MOSI(19), SPI1_MISO(21), SPI1_SCK(23) and SP1_CS0(24)) and tried to read the value of the potentiometer. However, the output result was 0.0V.

With the help of various people, I enabled SPI1 of Xavier.
I maked spidev1.0 occurred at /dev/ directory . However, when running the following program, the value will be 0.0 V.

import spidev
Vref = 3.3
ch0 = [0x06,0x00,0x00]
 
spi = spidev.SpiDev()
spi.open(1,0) #spi1.0
spi.max_speed_hz = 1000000 # 1MHz
time.sleep(0.05)
 
adc = spi.xfer2(ch0)

data = ((adc[1] & 0x0f) << 8) | adc[2]
print(str(Vref*data/4095) + "V")
 
spi.close()

The SPI device voltage level is 3.3V.
I used JetPack4.2.
It has been confirmed using Arduino that the devices are not broken.

What should I do?

Thanks.

snarky · July 9, 2019, 7:44pm

If you hook up a logic analyzer or storage scope on the clock and data lines of the SPI device, what do you see on the wires? Does the clock go out? Does the chip select go low? Does data go out/in?

Gaosiy · July 10, 2019, 3:09am

Do you use the spidev_test.c to test the self loop when connect MISO and MOSI?

bump5236 · July 10, 2019, 5:03am

Thanks.

I used storage scope.
But, there were no data.

Is there anything else to do?

bump5236 · July 10, 2019, 5:06am

Thank you for your reply.

The results I tried that:

hoge@hoge:~/Documents/c++/spi$ sudo ./spidev_test 
[sudo] password for hoge:
open device : /dev/spidev1.0
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 KHz)
RX | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | ................................

This doesn’t seem to work.
I changed to /dev/spidev1.0.

spidev_test.c

L.35 static const char *device = "/dev/spidev1.0";

Is there anything else to change?

Gaosiy · July 10, 2019, 7:21am

Have you changed the pinmux for extension header?

bump5236 · July 10, 2019, 9:41am

No.
I don’t know how to change it.
What file should I change and how to change it ?

ShaneCCC · July 11, 2019, 2:51am

Have a check below topic.

[url]https://devtalk.nvidia.com/default/topic/1049170/jetson-agx-xavier/spi1-not-work-on-xavier/post/5325856/#5325856[/url]

Gaosiy · July 11, 2019, 7:09am

You can try Shane’s method, unfortunately, I try it but it does not work. You can try to change the pinmux first, then we can talk it again.

bump5236 · July 12, 2019, 7:07am

Thanks a lot !

I have two more questions.
1)
“tegra19x-mb1-pinmux-p2888-0000-a04-p2822-0000-b01.cfg” is in 3 places, bootloader, bootloader/t186ref/BCT and sources/hardware/nvidia/platform/t19x/galen/bct/pinmux .
So which file should I change ?

After changing the file, can I flush the kernel with the following command ?

sudo ./flash.sh -k kernel-dtb jetson-xavier mmcblk0p1

Gaosiy · July 12, 2019, 7:15am

Thanks a lot !

I have two more questions.
1)
“tegra19x-mb1-pinmux-p2888-0000-a04-p2822-0000-b01.cfg” is in 3 places, bootloader, bootloader/t186ref/BCT and sources/hardware/nvidia/platform/t19x/galen/bct/pinmux .
So which file should I change ?

After changing the file, can I flush the kernel with the following command ?
sudo ./flash.sh -k kernel-dtb jetson-xavier mmcblk0p1

I think you should use pinmux xml and a python script to create the .cfg file, and then replace the original file at bootloader/t186xx, unfortunately, I use this method to change pinmux but it does not work, I don’t know why, you can try again, hope you can make it work.
the command should be used as you type out.

bump5236 · July 12, 2019, 7:36am

Thanks Gaosiy!

I’ll try them.

Gaosiy · July 12, 2019, 7:40am

If you have some progress, can you show it out?

bump5236 · July 12, 2019, 9:39am

Should I do the following?

Download the pinmux spreadsheet from the Jetson Download Center
Jetson Download Center | NVIDIA Developer
Change the contents of the sheet
Click the “Generate DT File” button to create dtsi files
Execute the dts2cfg to generate cfg file

If so, where should I change??

Gaosiy · July 12, 2019, 9:46am

you need find the pull botton to change the different function of a pin, then click the Generate DT file

bump5236 · July 16, 2019, 8:15am

Thanks to everyone, I was able to make spi enable.

I did the following.

Flash the Xavier using SDK manager
This is because Xavier boot failed.
Edit the following line of the JetPack_4.2_Linux_P2888/Linux_for_Tegra/bootloader/t186ref/BCT/tegra19x-mb1-pinmux-p2888-0000-a04-p2822-0000-b01.cfg

pinmux.0x0243d040 = 0x00000400; # spi1_sck_pz3: rsvd1, pull-down, tristate-enable, input-enable, lpdr-disable
pinmux.0x0243d020 = 0x00000450; # spi1_miso_pz4: rsvd1, pull-down, tristate-enable, input-enable, lpdr-disable
pinmux.0x0243d058 = 0x00000400; # spi1_mosi_pz5: rsvd1, pull-down, tristate-enable, input-enable, lpdr-disable
pinmux.0x0243d010 = 0x00000400; # spi1_cs0_pz6: rsvd1, pull-up, tristate-enable, input-enable, lpdr-disable
pinmux.0x0243d050 = 0x00000400; # spi1_cs1_pz7: rsvd1, pull-up, tristate-enable, input-enable, lpdr-disable

$ cd JetPack_4.2_Linux_P2888/Linux_for_Tegra/kernel/dtb/
$ dtc -I dtb -O dts -o /tmp/tegra194-p2888-0001-p2822-0000_test.dts tegra194-p2888-0001-p2822-0000.dtb
$ gedit /tmp/tegra194-p2888-0001-p2822-0000_test.dts

spi@3210000 {
                            compatible = "nvidia,tegra186-spi";
                            reg = <0x0 0x3210000 0x0 0x10000>;
                            interrupts = <0x0 0x24 0x4>;
                            #address-cells = <0x1>;
                            #size-cells = <0x0>;
                            iommus = <0x2 0x20>;
                            dma-coherent;
                            dmas = <0x1e 0xf 0x1e 0xf>;
                            dma-names = "rx", "tx";
                            spi-max-frequency = <0x3dfd240>;
                            nvidia,clk-parents = "pll_p", "clk_m";
                            clocks = <0x4 0x87 0x4 0x66 0x4 0xe>;
                            clock-names = "spi", "pll_p", "clk_m";
                            resets = <0x5 0x5b>;
                            reset-names = "spi";
                            <u>status = "okay";</u>
                            linux,phandle = <0x172>;
                            phandle = <0x172>;
[u]                            spidev@0 {
                                          compatible = "spidev";
                                          reg = <0x0>;
                                          spi-max-frequency = <0x1312d00>;
                            };[/u]
              };

$ dtc -I dts -O dtb -o tegra194-p2888-0001-p2822-0000.dtb /tmp/tegra194-p2888-0001-p2822-0000_test.dts
$ sudo ./flash.sh -r jetson-xavier mmcblk0p1

It worked well. Thank you!!

bump5236 · July 16, 2019, 8:15am

Cancel post.

Gaosiy · July 16, 2019, 9:03am

that’s great!
do you test the spidev_test.c?

bump5236 · July 18, 2019, 8:53am

Yes !

3620254461 · January 12, 2020, 2:05pm

Hi bunmp5236!
I do what you say.But,it doesn’t work for me…
I still can’t find /dev/spidev* in my xavier.

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