Difference between revisions of "BeagleBone Black Enable SPIDEV"

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(Enabling SPIDEV with Cape Manager)
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= SPIDEV Interface =
 
= SPIDEV Interface =
 +
<br>
 
== Description ==
 
== Description ==
 
SPI devices have a limited userspace API, supporting basic half-duplex
 
SPI devices have a limited userspace API, supporting basic half-duplex
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they need to access kernel interfaces (such as IRQ handlers or other layers
 
they need to access kernel interfaces (such as IRQ handlers or other layers
 
of the driver stack) that are not accessible to userspace.
 
of the driver stack) that are not accessible to userspace.
 
+
<br>
 
== References ==
 
== References ==
 
 
* [https://www.kernel.org/doc/Documentation/spi/spidev SPIDEV Kernel Documentation]
 
* [https://www.kernel.org/doc/Documentation/spi/spidev SPIDEV Kernel Documentation]
 
* [http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus SPI Wikipedia Page]
 
* [http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus SPI Wikipedia Page]
 
* [http://omapedia.org/wiki/PandaBoard_SPI SPIDEV on PandaBoard.org (good examples)]
 
* [http://omapedia.org/wiki/PandaBoard_SPI SPIDEV on PandaBoard.org (good examples)]
 
* [https://raw.github.com/torvalds/linux/master/Documentation/spi/spidev_test.c spidev-test application]
 
* [https://raw.github.com/torvalds/linux/master/Documentation/spi/spidev_test.c spidev-test application]
 
+
<br>
 +
<br>
 
= Enabling SPIDEV with Cape Manager =
 
= Enabling SPIDEV with Cape Manager =
 +
<br>
 
== SPI1 ==
 
== SPI1 ==
 
<div style="margin:0; margin-top:10px; margin-right:10px; border:1px solid #dfdfdf; padding:0 1em 1em 1em; background-color:red; align:right; ">
 
<div style="margin:0; margin-top:10px; margin-right:10px; border:1px solid #dfdfdf; padding:0 1em 1em 1em; background-color:red; align:right; ">
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cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups
 
cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups
 
</pre>
 
</pre>
 
+
<br>
 
== SPI0 ==
 
== SPI0 ==
 
 
 
 
 
Start nano
 
Start nano
 
<pre>
 
<pre>

Revision as of 03:18, 16 July 2013

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


SPI1

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

Start nano

nano BB-SPI1-01-00A0.dts


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

/dts-v1/;
/plugin/;

/ {
    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 = <1>;
                 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