BeagleBone Black Enable SPIDEV

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SPIDEV Interface


Description

SPI devices have a limited userspace API, supporting basic half-duplex read() and write() access to SPI slave devices. Using ioctl() requests, full duplex transfers and device I/O configuration are also available.

	#include <fcntl.h>
	#include <unistd.h>
	#include <sys/ioctl.h>
	#include <linux/types.h>
	#include <linux/spi/spidev.h>


Some reasons you might want to use this programming interface include:

  • Prototyping in an environment that's not crash-prone; stray pointers in userspace won't normally bring down any Linux system.
  • Developing simple protocols used to talk to microcontrollers acting as SPI slaves, which you may need to change quite often.


Of course there are drivers that can never be written in userspace, because they need to access kernel interfaces (such as IRQ handlers or other layers of the driver stack) that are not accessible to userspace.

References



Enabling SPIDEV with Cape Manager


NOTE: You CAN NOT use SPI1 on the BeagleBone Black WITHOUT disabling the HDMI interface



SPI1 D1 Output and D0 Input

Start nano

nano BB-SPI1-01-00A0.dts


Copy-paste this into the file(or download a copy BB-SPI1-00A0):

/dts-v1/;
/plugin/;

/* SPI1 */
/* D1 Output and D0 Input */

/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";

    /* identification */
    part-number = "spi1mux";

    fragment@0 {
        target = <&am33xx_pinmux>;
        __overlay__ {
            spi1_pins_s0: spi1_pins_s0 {
                        pinctrl-single,pins = <
                                0x190 0x33      /* mcasp0_aclkx.spi1_sclk, INPUT_PULLUP | MODE3 */
                                0x194 0x33      /* mcasp0_fsx.spi1_d0, INPUT_PULLUP | MODE3 */
                                0x198 0x13      /* mcasp0_axr0.spi1_d1, OUTPUT_PULLUP | MODE3 */
                                0x19c 0x13      /* mcasp0_ahclkr.spi1_cs0, OUTPUT_PULLUP | MODE3 */
                >;
            };
        };
    };

    fragment@1 {
        target = <&spi1>;
        __overlay__ {

             #address-cells = <1>;
             #size-cells = <0>;
             status = "okay";
             pinctrl-names = "default";
             pinctrl-0 = <&spi1_pins_s0>;

             spidev@1 {
                 spi-max-frequency = <24000000>;
                 reg = <0>;
                 compatible = "linux,spidev";
            };
        };
    };
};

Close the file (Ctrl-o, Ctrl-x) and compile using dtc:

dtc -O dtb -o BB-SPI1-01-00A0.dtbo -b 0 -@ BB-SPI1-01-00A0.dts

Then, copy the file into /lib/firmware/:

 cp BB-SPI1-01-00A0.dtbo /lib/firmware/

Then enable the device tree overlay:

 echo BB-SPI1-01 > /sys/devices/bone_capemgr.*/slots

Plug in your BBB to a host computer using the mini usb data cable.

Go to My Computer>BeagleBone Getting Started> and open uEnv.txt Copy and paste this command into the .txt file. Make sure to save your changes. (Ctrl+s)

optargs=quiet drm.debug=7 capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN
capemgr.enable_partno=BB-SPI1-01

after you save the changes, reboot your beaglebone black
Make sure it is enabled You should now have two spidev-files in the folder /dev/

ls -al /dev/spidev1.*

You should also be able to see the pingroups:

cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups



SPI1 D0 Input and D1 Output

Start nano

nano BB-SPI1-01-00A0.dts


Copy-paste this into the file(or download a copy BB-SPI1-00A0):

NOTE: an option is available to swap the MISO/MOSI pins using the device tree entry. to enable the pin swap change the feature section by adding “ti,pindir-d0-out-d1-in" property and changing the default pin mux for the two data pins

/dts-v1/;
/plugin/;

/* SPI1 */
/* D0 Output and D1 Input */

/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";

    /* identification */
    part-number = "spi1mux";

    fragment@0 {
        target = <&am33xx_pinmux>;
        __overlay__ {
            spi1_pins_s0: spi1_pins_s0 {
                        pinctrl-single,pins = <
                                0x190 0x33      /* mcasp0_aclkx.spi1_sclk, INPUT_PULLUP | MODE3 */
                                0x194 0x13      /* mcasp0_fsx.spi1_d0, OUTPUT_PULLUP | MODE3 */
                                0x198 0x33      /* mcasp0_axr0.spi1_d1, INPUT_PULLUP | MODE3 */
                                0x19c 0x13      /* mcasp0_ahclkr.spi1_cs0, OUTPUT_PULLUP | MODE3 */
                >;
            };
        };
    };

    fragment@1 {
        target = <&spi1>;
        __overlay__ {

             #address-cells = <1>;
             #size-cells = <0>;
             status = "okay";
             pinctrl-names = "default";
             pinctrl-0 = <&spi1_pins_s0>;
             ti,pindir-d0-out-d1-in = <1>;

             spidev@1 {
                 spi-max-frequency = <24000000>;
                 reg = <0>;
                 compatible = "linux,spidev";
            };
        };
    };
};

Close the file (Ctrl-o, Ctrl-x) and compile using dtc:

dtc -O dtb -o BB-SPI1-01-00A0.dtbo -b 0 -@ BB-SPI1-01-00A0.dts

Then, copy the file into /lib/firmware/:

 cp BB-SPI1-01-00A0.dtbo /lib/firmware/

Then enable the device tree overlay:

 echo BB-SPI1-01 > /sys/devices/bone_capemgr.*/slots

Plug in your BBB to a host computer using the mini usb data cable.

Go to My Computer>BeagleBone Getting Started> and open uEnv.txt Copy and paste this command into the .txt file. Make sure to save your changes. (Ctrl+s)

optargs=quiet drm.debug=7 capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN
capemgr.enable_partno=BB-SPI1-01

after you save the changes, reboot your beaglebone black
Make sure it is enabled You should now have two spidev-files in the folder /dev/

ls -al /dev/spidev1.*

You should also be able to see the pingroups:

cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups


SPI0

Start nano

nano BB-SPI0-01-00A0.dts


Copy-paste this into the file(or download a copy BB-SPI0-00A0):

/dts-v1/;
/plugin/;

/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";

    /* identification */
    part-number = "spi0pinmux";

    fragment@0 {
        target = <&am33xx_pinmux>;
        __overlay__ {
            spi0_pins_s0: spi0_pins_s0 {
                pinctrl-single,pins = <
                  0x150 0x30  /* spi0_sclk, INPUT_PULLUP | MODE0 */
                  0x154 0x30  /* spi0_d0, INPUT_PULLUP | MODE0 */
                  0x158 0x10  /* spi0_d1, OUTPUT_PULLUP | MODE0 */
                  0x15c 0x10  /* spi0_cs0, OUTPUT_PULLUP | MODE0 */
                >;
            };
        };
    };

    fragment@1 {
        target = <&spi0>;
        __overlay__ {
             #address-cells = <1>;
             #size-cells = <0>;

             status = "okay";
             pinctrl-names = "default";
             pinctrl-0 = <&spi0_pins_s0>;

             spidev@0 {
                 spi-max-frequency = <24000000>;
                 reg = <0>;
                 compatible = "linux,spidev";
            };
        };
    };
};

Close the file (Ctrl-o, Ctrl-x) and compile using dtc:

dtc -O dtb -o BB-SPI0-01-00A0.dtbo -b 0 -@ BB-SPI0-01-00A0.dts

Then, copy the file into /lib/firmware/:

 cp BB-SPI0-01-00A0.dtbo /lib/firmware/

Then enable the device tree overlay:

 echo BB-SPI0-01 > /sys/devices/bone_capemgr.*/slots
optargs=quiet drm.debug=7 capemgr.enable_partno=BB-SPI0-01

after you save the changes, reboot your beaglebone black

Make sure it is enabled You should now have two spidev-files in the folder /dev/

ls -al /dev/spidev0.*

You should also be able to see the pingroups:

cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups


You can also try to run a loopback test with beaglebone. Here is an example with loopback on SPI1 bus:

1. Short pins 29 and 30 on the P9 connector (power supply side on the board).

2. Apply the following diff to the kernel:

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index 911e9e0..622adf5 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -646,6 +646,7 @@ static int spidev_remove(struct spi_device *spi)
 
 static const struct of_device_id spidev_dt_ids[] = {
        { .compatible = "rohm,dh2228fv" },
+       { .compatible = "linux,spidev" },
        {},
 };

3. Run the spidev_test program (sources in kernel/Documentation/spi), the following is a typical log:

bash-4.2# /spidev_test -D /dev/spidev1.0
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

FF FF FF FF FF FF 
40 00 00 00 00 95 
FF FF FF FF FF FF 
FF FF FF FF FF FF 
FF FF FF FF FF FF 
DE AD BE EF BA AD 
F0 0D